Life tables provide a summary of mortality and reproductive schedules and can help explain why certain species proliferate in particular environments. Life table characteristics of Anopheles arabiensis, under a range of simulated seasonal temperature were determined. F₁ progeny of field-collected material were observed at four fluctuating temperatures with means of 17.9, 23.2, 26.1, and 21.4°C, representing winter, spring, summer and autumn temperature profiles. Gonotrophic cycles, egg hatchability rates, mean male and female lifespans, reproductive rate, the intrinsic rate of increase, and generation times were calculated. Immature development was fastest in summer (11 d) compared with winter (32 d), resulting in less robust adults. Mean female lifespans were greater than those of the males and also increased with decreasing temperatures. From the age-specific survivorship curve and the gonotrophic cycles, females were found to lay large numbers of eggs especially during spring and summer. Under simulated winter conditions mosquitoes did not oviposit in the laboratory. It was also determined that summer reared mosquitoes are capable of giving just one infected bite while autumn reared mosquitoes can give two infected bites, increasing their transmission potential. Thus life table data go some way toward explaining late season transmission of malaria in South Africa.

Three California Culex species previously identified as efficient laboratory vectors of West Nile (WN) virus were tested for their capability to vertically transmit WN virus. Wild-caught Culex pipiens pipiens L., Culex pipiens quinquefasciatus Say, and two populations of Culex tarsalis Coquillett females were inoculated intrathoracically with 10^{2.7 ± 0.1} plaque-forming units of WN virus. F₁ progeny were reared at 18°C and subsequently tested as adults for infectious virus on Vero cell culture. Virus was not detected in 197 pools comprising 4,884 Cx. p. pipiens. The minimum filial infection rate (MFIR) for Cx. p. quinquefasciatus was ≈3.0/1,000 for 665 progeny tested in 28 pools. There was no virus detected in 102 pools of 2,453 progeny from Cx. tarsalis collected in Riverside County. The MFIR for Cx. tarsalis collected in Yolo County was ≈ 6.9/1,000 for 2,165 progeny tested in 86 pools. Mosquito progeny infected vertically during the fall could potentially serve as a mechanism for WN virus to overwinter and initiate horizontal transmission the following spring.

Thoracic spiracle length and its index was examined for their ability to discriminate two ecological variants, type form and mysorensis, of Anopheles stephensi in the adult stage. The type form is exclusively domestic in all seasons, whereas the mysorensis variant occupies the outdoor niche during monsoon and postmonsoon seasons, with spillover into domestic sites during summer ecological stress periods. A statistically significant co-relation was established between the ridge count of the egg and two adult measurements, the thoracic spiracle length, and the spiracular index. In An. stephensi type form, average spiracle length was 0.11–0.12 mm and average spiracular index was 8.09–9.23, whereas in mysorensis, the corresponding figures were 0.09–0.10 mm and 6.82–7.60. These parameters showed consistent variations in population of mosquitoes that emerged during monsoon and summer season. The thoracic lengths in both variants remained constant, and only spiracular lengths showed fluctuations in three seasonal populations. These measures provide discrimination of adult variants—identifications that are essential in malaria control programs.

Canonical discriminant analysis accurately separated males of Lutzomyia yencanensis (n = 36) (Ortiz), Lutzomyia cayennensis cayennensis (n = 24) (Floch and Abonnenc) and Lutzomyia micropyga (n = 28) (Mangabeira). Only seven (length of head, interocular distance, wing vein δ, genital filaments, coxite, paramere, and lateral lobe) of 20 possible morphometric measurements were required for differentiation, with a highly significant canonical correlation. The discriminant equations provided a simple, fast, and widely available statistical tool to identify accurately unknown sand fly specimens as L. yencanensis, L. c. cayennensis, or L. micropyga.

An ultrastructural study of the heart of the tsetse fly, Glossina morsitans, and of several other species of cyclorraphan flies revealed that the ventral region of the heart of adult flies is supported by a muscular septum not present in the larval stage. The pericardial septum of the adult heart is composed laterally of alary muscles and a central longitudinal muscle that extends the length of the abdominal aorta, whereas the larval heart is supported ventrally only by alary muscles and strands of connective tissue. Thus, unlike the larval stage, and the heart of other insects, the pericardial septum of adult cyclorraphan flies contains a central band of longitudinal muscle, that along with the alary muscle, forms a large pericardial sinus lying between the septum and the heart. Neurosecretory nerves arising from the lateral nerves of the thoracicoabdominal ganglion extend dorsad to the pericardial septum, where they form neuromuscular junctions on the muscle fibers of the pericardial septum or traverse the septum terminating in the pericardial sinus, thereby creating one of the largest neurohemal organs in these flies. In the tsetse fly, some of the neurosecretory fibers also extend between the muscle fibers of the myocardium, and release their material into the lumen of the heart.

The larva of Argas (Persicargas) keiransi Estrada-Peña, Venzal & González-Acuña n. sp. is described from specimens collected on the neck of a chimango, Milvago c. chimango (Aves: Falconiformes) in the Chillán, Chile, in the Sub-Antarctic biogeographical region. The larva of the new species shares the tarsus I setal formula with A. (P.) giganteus, these being the only two Persicargas species with three pairs of ventral setae plus both av4 and pv4 setae. However, it is unique in having a dorsal plate “V” or “U” shaped, with the anterior end open, without the typical reticulated pattern present in the remaining species of the genus.

The ultrastructure and characteristics of hemocytes of argasid tick species, Ornithodoros moubata, during the ecdysdial phase are herein presented. Hemocyte classes/populations characterized based on their affinity with Giemsa stain and ultrastructural differences comprised the prohemocytes, nongranular cells (Nc), eosinophilic granular cells (Ec), basophilic granular cells (Bc), and unidentified cells. Significant changes/shift in the ratio of hemocyte classes/population was apparent in ticks before and after the ecdysial phase. The granule-scant basophilic granular cells (sBc) constituted the most abundant hemocyte population in the ecdysial phase. Nymphs in ecdysis showed increases in Nc and sBc and decrease in Ec, a phenomenon that was reversed in unengorged nymphs and adults ticks. The significant increase in total Bc population in ecdysis relative to nonengorged ticks clearly point to blastogenesis of Bc taking place during the ecdysial phase and Bc’s important role in the process of tissue remodeling.

A multitemporal, land use land cover (LULC) classification dataset incorporating distributions of mosquito larval habitats was produced in ERDAS Imagine using the combined images from the Multispectral Thermal Imager (MTI) at 5 m spatial resolution from 2001 with Thematic Mapper-classification data at 28.5 m spatial resolution from 1987 and 1989 for Kisumu and Malindi, Kenya. Total LULC change for Kisumu over 14 yr was 30.2%. Total LULC change for Malindi over 12 yr was 30.6%. Of those areas in which change was detected, the LULC change for Kisumu was 72.5% for nonurban to urban, 21.7% urban to nonurban, 0.4% urban to water, 4.5% water to urban, and 0.9% water to nonurban. The proportion of LULC change for Malindi was 93.5% for nonurban to urban, 5.9% urban to nonurban, 0.2% urban to water, 0.3% nonurban to water, and 0.1% water to urban. A grid (270 m × 270 m cells) was overlaid over the maps stratifying grid cells based on drainage and planning. Of 84 aquatic habitats in Kisumu, 32.1% were located in LULC change sites and 67.9% were located in LULC nonchange sites. Of 170 aquatic habitats in Malindi, 26.5% were located in LULC change sites and 73.5% were located in LULC nonchange sites. The most abundant LULC change per strata with anopheline habitats was unplanned and poorly drained. Ditches and puddles in Kisumu and car tracks in Malindi displayed the highest number of anopheline larval habitats for all LULC change sites. The proportion of site positive aquatic habitats for anopheline larvae was higher in LULC change sites than for LULC nonchange sites for Kisumu. This evidence suggests LULC change can influence anopheline larval habitat distribution.

During the rainy season of 2001, the incidence of the dengue vectors Aedes aegypti and Ae. albopictus was examined in different habitats of two cities (Rio de Janeiro and Nova Iguaçu) in Rio de Janeiro State, Brazil, and in two cities (Palm Beach and Boca Raton) in Florida. Oviposition trap collections were performed in urban, suburban, and rural habitats in both areas. Our hypothesis that the abundances and frequencies of occurrence of Ae. aegypti and Ae albopictus are affected in opposite ways by increasing urbanization was only partially supported. City, habitat, and their interaction significantly affected the abundance of both species. Cities with high abundance of Ae. aegypti also had a high abundance of Ae. albopictus. The two species were most abundant in the cities of Rio de Janeiro state and the lowest in Boca Raton. Habitat had a significant but opposite effect on the abundances of Ae. aegypti and Ae. albopictus. In general, Ae. aegypti was most prevalent in highly urbanized areas and Ae. albopictus in rural, suburban, and vegetated urban areas in Rio de Janeiro state and Florida. However, abundances of the two species were similar in most suburban areas. Analyses of frequencies of occurrence showed an unexpected high level of co-occurrence of both species in the same oviposition trap. Despite the different geographical origins of Ae. albopictus in Brazil and the United States, the habitats used by this recent invader are remarkably similar in the two countries.

An automated feeding apparatus was developed to maintain the human head louse (Pediculus capitis DeGeer) in vitro. With the use of valves and timers, banked human blood and saline from refrigerated reservoirs were pumped into and flushed out of the system every 7 d. During this rotational interval, bloodmeals were provided to head lice continuously and ad libitum through a stretched Nescofilm-silicone sandwich membrane. Compared with our previous in vitro human head louse-rearing apparatus, greater numbers of lice could be fed simultaneously with minimal human monitoring. Development of second to third instars and third instars to adults was significantly faster when lice were reared in vivo than on either of the in vitro rearing systems; there was no significant difference in the duration of the first instar. Although fecundity and hatch rates were significantly higher for female lice reared in vivo, similar trends have been observed for other membrane-fed arthropods. Body lice (Pediculus humanus L.) and bed bugs (Cimex lectularius [L.]) also completed most of their life cycle on this apparatus. Our automated mass-rearing system has broad applications for maintaining fluid-sucking ectoparasites and will facilitate various toxicological, behavioral, and disease-transmission investigations.

Dispersion and invasion capacity of sylvatic populations of Triatoma dimidiata (Latreille) were investigated during 14 mo by means of experimental chicken coops installed in a nature reserve within the Maya Biosphere, Petén, Guatemala. In addition, palm trees, underground archeological holes (chultunes) and piles of limestones within the forest were inspected as potential sylvatic habitats of T. dimidiata. From the three types of sylvatic habitats we inspected, all served as shelter and breeding sites for T. dimidiata. The natural infection of these bugs (n = 72) with Trypanosoma cruzi (Chagas) was high (25%) and represent a risk for humans who colonize the forest. T. dimidiata quickly invaded the experimental chicken coops installed in the primary forest, albeit at very low densities. However, only one adult bug was encountered in the chicken coops installed in a secondary forest. Dispersal of adult T. dimidiata was most apparent at the end of the dry season. Overall, our results indicate a potential risk for invasion by sylvatic T. dimidiata of domestic environments in this area, with a risk of T. cruzi transmission to humans. We suggest that a system of community-based surveillance should be developed to detect new infestations and organize prompt treatment of any new cases of acute Chagas disease that may result.

Biting midges (Diptera: Ceratopogonidae) were collected at 16 periurban and rural sites around Iquitos, Peru, between 17 October 1996 and 26 May 1997. Culicoides paraensis (Goeldi), the principal vector of Oropouche virus, was the most commonly collected species (9,086 flies) with Culicoides insinuatus Wirth & Blanton second (7,229 flies). Although both species were collected at all sampling sites (linear distance surveyed ≈25 km), C. paraensis dominated at northern collection sites (>90%), whereas C. insinuatus prevailed at southern collection sites (>60%). C. paraensis were collected from human sentinels at a constant rate throughout daylight hours, at similar rates during wet and dry months, and regardless of rainfall. Larval developmental substrates for C. paraensis included decaying platano (Musa × paradisiaca L. [Musaceae]) stems, stumps, flowers, fruits, and debris beneath platano trees as well as from soil beneath a fruiting mamay (Syzygium malaccense Merr. & Perry [Myrtaceae]) tree and organic-rich mud along a lake shoreline. C. insinuatus adults likewise emerged from decaying platano and organic-rich mud along a lake shoreline, but also from debris accumulated in the axils of aguaje (Mauritia flexuosa L. [Palmae]) fronds and decaying citrus fruit. Despite high numbers of biting adults near putative substrates, adults of neither species emerged from other decomposing plant material, soil, phytotelmata, or artificial containers. Because both species of biting midges emerged in high numbers from all parts of platano (ubiquitous in Iquitos), it will be challenging to control them through sanitation.

Between April and October 1997, 689 bats representing seven species were captured at Pennsylvania’s Canoe Creek State Park. Each bat was sampled for ectoparasitic arthropods, and four species were collected from 13.2% of the host individuals. Ectoparasites include the bat flea Myodopsylla insignis (Rothschild), the wing mite Spinturnix americanus (Banks), the bed bug Cimex adjunctus Barber, and the soft tick Ornithodoros kelleyi Cooley & Kohls. Prevalence, relative density, and mean intensity were calculated for ectoparasites of Myotis lucifugus (Le Conte), which harbored all four ectoparasite species and was the most commonly captured host. Patterns of ectoparasite associations were examined with respect to host sex and habitat (roost characteristics). Female M. lucifugus hosted higher densities of ectoparasites than did males. Moreover, relative densities of ectoparasites from M. lucifugus were dependent on the proximate roost; hosts captured near Bat Church were more heavily parasitized than those captured near Hartman Mine. Two other bat species were infested with at least one ectoparasite, but sample sizes were too small to analyze statistically. These bat species included Myotis septentrionalis (Trouessart), harboring M. insignis, S. americanus, and O. kelleyi, and Eptesicus fuscus (Beauvois), which harbored M. insignis and O. kelleyi.

Three potentially important aspects of mark-release-recapture experimentation were addressed: 1) source of mosquitoes for release, 2) time of release, and 3) weather during recapture. Culex tarsalis Coquillett mosquitoes collected as adult host-seeking females from dry ice-baited traps (CO₂ traps) operated within the study area (local) were recaptured more frequently than females collected from traps operated outside the study area (foreign) or reared from field-collected immatures (reared). These results supported published studies on Anopheles and Ochlerotatus that indicated mosquitoes may “memorize” flight paths within their environment. Releasing gravid females provided a potentially useful replacement for reared females, because these gravids oviposited at wetlands and then dispersed to upland traps. Releasing local, foreign, or reared mosquitoes just after sunrise or just before sunset did not alter recapture success or the distance dispersed. Elevated wind speeds inhibited dispersal from protected microhabitats with citrus orchards and resulted in most recaptures being found at the leeward portion of the orchard.

Progressive changes in the attraction of waters harboring pre-imago populations of Aedes aegypti exposed to different levels of the entomopathogenic digenean Plagiorchis elegans to ovipositing conspecific females were assessed under conditions of optimal food availability. The impact of ovipositional preference and parasitic infection on population structure and development was investigated. Probabilities that larvae progress from one stage to the next or die within 24 h were calculated for all life stages. Exposure to P. elegans cercariae did not significantly affect the attractiveness of larval-holding waters. Ovipositional preference increased significantly with growing biomass of the larval population, with the event of pupation and, in some cases, with late instar mortality. Exposure to various levels of the parasite significantly increased mortality of all instars, but most of the damage caused by the parasite occurred in the form of increased pupal mortality and decreased adult emergence. Exposure to the parasite significantly reduced the number of adults produced yet did not impair larval development. Thus, larval recruitment into environments containing P. elegans remains high, the structure of larval populations remains relatively normal, but few adults are produced.

The responses of Aedes albopictus to sources of oviposition attractants and stimulants were evaluated with a behavioral bioassay in which females attracted to odorants emanating from water were trapped on screens coated with an adhesive. Gravid mosquitoes were attracted to volatiles from larval-rearing water and soil-contaminated cotton towels. Bacteria were isolated from these substrates and from an organic infusion made with oak leaves. Through fatty acid-methyl ester analyses, six bacterial isolates from larval-rearing water, two isolates from soil-contaminated cotton towels, and three isolates from oak leaf infusion were identified to species. The response of gravid mosquitoes to these isolates was also evaluated in behavioral bioassays. Water containing Psychrobacter immobilis (from larval-rearing water), Sphingobacterium multivorum (from soil-contaminated cotton towels), and an undetermined Bacillus species (from oak leaf infusion) elicited significantly higher oviposition than control water without bacteria. Only volatiles collected from larval rearing water elicited significant electroantennogram responses in females.

Chemical analysis (high-performance liquid chromatography) and bioassay demonstrated the presence of compounds that seem to be components of the Ixodes scapularis arrestment pheromone. Only two purines, guanine and xanthine, were found in acidified saline extracts made from cast skins after molting of fed nymphs, fed larvae, and fecal/excretory exudates deposited by unfed adults on substrates in their environment. The ratio of guanine to xanthine was 10.6:1 in an extract from the nymphal skins versus 0.95:1 in an extract from the larval skins. Guanine, xanthine, and traces of a third purine, tentatively identified as 8-azaguanine, were found in extracts made from filter paper strips or washings from glass vials contaminated with tick feces and excreta left by unfed adults. 8-azaguanine may be a product of microbial degradation of the other purines rather than a natural product from the ticks. Low concentrations of ammonia also were detected in saline extracts of excreta from feeding ticks. Hematin also was found in NH₄OH extracts of the black fecal/excretory exudates deposited by the unfed ticks. Hematin was tentatively identified by comparison of spectra with that of the authentic standard. Bioassays demonstrated a strong positive arrestment response to cast skins found to contain a mixture of guanine and xanthine and to black fecal/excretory exudates containing guanine, xanthine, the putative 8-azaguanine, and hematin. A Noldus video tracking system using a CCD video camera and Ethovision Pro tracking software showed statistically significant increases in the frequency of visits to the treated zone versus the control. Ticks were significantly more likely to assemble in response to the tick exudates within as little as 3 h compared with the controls. Previous bioassay studies also showed strong positive responses to guanine, xanthine, other purines, and hematin. Comparisons with the arrestment pheromones of other tick species are described. The inclusion of the pheromone components in a permethrin-impregnated oily matrix, Last Call, increased the lethal activity of the product to 95% compared with only 65% in the formulation with permethrin alone. More detailed knowledge of I. scapularis arrestment pheromone may be useful for improving the efficacy of this tick-killing technology even further.

To explain how larval Anopheles arabiensis Patton feed effectively in the turbid water in which they frequently develop, we determined whether an extractable component of maize, Zea mays L., pollen enhances feeding by these mosquitoes. Maturing maize produces a copious amount of wind-borne pollen that is nutritious enough and produced over a sufficient period to support the development of at least one generation of anopheline mosquitoes. Larval An. arabiensis readily ingest the contents of maize pollen or the intact pollen grains themselves. An aqueous extract of maize pollen markedly accelerates the rate at which larval An. arabiensis ingest inert particles and strongly enhances the effectiveness of Bti against larval An. arabiensis. We conclude that the ability of larval anopheline mosquitoes to feed on maize pollen in turbid water is enhanced by the release from these pollen grains of a water-soluble phagostimulatory component (or components), which may be used to increase ingestion of microbial entomotoxins.

Two groups of Anopheles claviger sensu stricto Meigen (Diptera: Culicidae) were recently found in France, representing unclear genetic entities. To better understand this situation, sampling was extended to 13 European countries, and 47 samples were analyzed by investigating the polymorphism of 11 autosomal and 1 sex-linked allozyme loci. Genetic differentiation, as measured by F_st, between these two groups was confirmed, with no isolation by distance within each group. Among the twelve loci studied, none had diagnostic alleles. Group I is mainly located in western Europe (UK and south-west of France), and Group II covers eastern France and eastern and northern Europe. Intermediate populations, sampled at the overlapping range between them, do not display a heterozygote deficit, suggesting that these two groups are probably not genetically isolated. The origin of each group and its biological significance is discussed within the context of differentiation in refugia during recent glaciations.

Anopheline mosquito larvae and adults were sampled at Ban Pu Teuy, Tri-Yok District, Kanchanaburi Province, western Thailand, from January 2000 to December 2001. Over the period of 2 yr, Anopheles minimus sensu lato was the most commonly collected species, followed by Anopheles swadiwongporni and Anopheles dirus sensu lato; all three species are important vectors of malaria in Thailand. Attempted blood feeding by An. minimus occurred throughout the night, with two distinct feeding peaks: strong activity immediately after sunset (1800–2100 hours), followed by a second, less pronounced, rise before sunrise (0300–0600 hours). Anopheles minimus were more abundant during the wet season compared with the dry and hot seasons, although nocturnal adult feeding patterns were similar. Anopheles minimus fed readily on humans inside and outside of houses, showing a slight preference for exophagy. The human-biting peak of An. minimus in our study area differed from other localities sampled in Thailand, indicating the possible existence of site-specific populations of An. minimus exhibiting different host-seeking behavior. These results underscore the importance of conducting site-specific studies to accurately determine vector larval habitats and adult activity patterns and linking their importance in malaria transmission in a given area.

Culex (Culex) pipiens quinquefasciatus Say field population from Vero Beach, FL, sampled monthly over a period of 8 mo, a colony sample, and six geographic samples were analyzed for genetic variation at 12 enzymes (10 “neutral” gene enzymes with 11 putative loci and two “complex” gene enzymes) by using polyacrylamide gel electrophoresis. The analysis of the 11 putative loci in both temporal and geographic samples showed that the four loci (Gpi, Hk, Mdhp-2, and Pgm) diagnostic of Cx. p. quinquefasciatus in the southern United States are present in similar frequencies in Florida samples. The Cx. p. quinquefasciatus colony sample showed significantly lower genetic variation than the temporal field samples, measured by mean number of alleles per locus (colony 1.2 ± 0.1 versus field 1.44 ± 0.03), percentage of polymorphic loci (colony 18.2% versus field 28.4%), mean observed heterozygosity (H_o = colony 0.027 ± 0.02 versus field 0.09 ± 0.01), and mean Hardy-Weinberg expected heterozygosity (H_e = colony 0.025 ± 0.02 versus field 0.085 ± 0.01). Three of the 11 loci (Acoh, Pgd, and Pgm) from the Vero Beach field samples showed bimodal patterns in their frequencies of the most common allele during peak density of the population. The low value of F_st of 0.058 indicated minimum population substructuring among the temporal samples. Genetic variability values between geographic samples from the Florida panhandle and south Florida were not significant. Gene flow estimates based on F_ST = 0.05, indicating low levels of gene flow among the geographic samples of Cx. p. quinquefasciatus. The average Nei’s and modified Rogers’ genetic distances among the six populations were 0.005 ± 0.001 and 0.077 ± 0.007, respectively. The cluster analysis did not suggest geographic clustering. The analysis of the “complex” gene enzymes in both temporal and geographic samples of Cx. p. quinquefasciatus from Florida showed the presence of two highly amplified esterases (Estβ1 and Estα2\Estβ2), indicating resistance to organophosphate insecticides and highly amplified Aldox enzyme (an enzyme that indicates resistance to at least one insecticide and a herbicide). Comparison of our results with previous studies on Cx. p. quinquefasciatus populations in the United States indicates that the genetic characteristics of the Florida populations of Cx. p. quinquefasciatus are very similar to populations from areas where ecological conditions are very different.

Two putative cDNAs of acetylcholinesterase (AChE), one from Dermacentor variabilis, and the other from Rhipicephalus sanguineus, were amplified and sequenced. The deduced amino acid sequences have high amino acid identities (between 70 and 94%) to known tick AChE sequences deposited in GenBank. Furthermore, these two AChEs also possess common features in their primary AChE structure such as catalytic active sites. A 2,220-bp contiguous sequence, containing a 1,791-bp open reading frame encoding an AChE precursor with 596 amino acid residues, was obtained from D. variabilis. The deduced proteins of R. sanguineus are different in size by 6 amino acids because of alternative splicing at the 5′ end. A gene tree deduced from phylogenetic analysis indicates that there are at least three lineages of AChE in arthropods.

Field and laboratory investigations were undertaken to determine the level of expression of autogeny in the mosquito Ochlerotatus vigilax (Skuse) from southeast Queensland, Australia, and whether there was evidence of seasonal variation. At two field sites in southeast Queensland, Wellington Point and Donnybrook, autogeny rates were determined on six occasions between January 2001 and January 2002. The autogeny rate varied between 71 and 100% at Wellington Point and between 63 and 100% at Donnybrook. Autogenous fecundity ranged from 17 to 63 eggs per female at Wellington Point and from 13 to 88 eggs per female at Donnybrook. Positive relationships were found between adult body size (indicated by wing length), autogeny rate, and fecundity. A laboratory study was conducted to investigate the influence of larval nutrition and adult diet (water versus sucrose) on the expression of autogeny. The autogeny rate at a low-diet treatment was between 73 and 90% when sucrose was withheld from females and 100% when sucrose was provided. All high-diet females were autogenous. Autogenous egg development required 80 ± 6 h from emergence at 27°C. We conclude that autogeny rates are consistently high in Oc. vigilax from the southeast Queensland region.

We used flow-through respirometry on female mosquitoes to observe individual ventilatory pattern and to measure metabolic rate at rest, during activity and after a blood-meal. At rest, young adult females of the species Culex tarsalis ventilated cyclically with an average VCO₂ of 65 nl/min and frequency of 45 mHz. Both resting metabolic rate and body mass of females increased between emergence and 4 d, but only body mass continued to increase until 12 d. Mating status had no effect on the body mass or resting metabolic rate of the females. Both lipid and carbohydrate stores strongly increased during the first week of adult life, in particular between emergence and 4 d, in which lipid mass increased 8.3-fold and carbohydrate mass increased 3.6-fold. Hourly metabolic rate after a blood or sugar meal was measured over a 6-d period in two groups of 14 females. Sugar-fed mosquitoes remained calm during the day and had nocturnal increases in metabolic rate associated with flight activity. Blood feeding elicited a specific dynamic action lasting ≈55 h, at the peak of which metabolic rate of the blood-fed females was twice that of the sugar-fed group. Eggs were laid on the third night. The increase in metabolic rate presumably reflected the cost of blood digestion and egg production. The females were not active during digestion, so that although their metabolic rate was increased, the overall energy expenditure of the blood-fed group was not very different from that of the sugar-fed group.

A single village control trial for Triatoma pallidipennis and T. barberi was conducted using three synthetic pyrethroids (bifenthrin, cyfluthrin, and deltamethrin), evaluated as residual treatments in separate sectors, with complete coverage indoors and in peridomiciliary areas. Spray intervention was preceded by a preintervention entomological evaluation and household survey, followed by four postintervention evaluations at 1, 3, 6, and 12 mo of >96% of houses. Overall preintervention adjusted infestation index was 38%, 17% of which represented intradomicile infestation. Dose verification using high-performance liquid chromatography (HPLC) demonstrated correct spray doses for all but deltamethrin treatments. There was between a 6- and 13-fold decrease in intradomicile live bug infestation for cyfluthrin- and bifenthrin-treated areas, resulting at 1 mo in 0 and 0.6% infestation, respectively. Intradomicile infestation recovered somewhat, terminating at 20 and 50% of preintervention levels at 12 mo, respectively, while peridomicile infestation recovered preintervention levels within 3–6 mo. Households with persistent live peridomiciliary infestation had 1.9 times the risk of having a persistent intradomiciliary infestation, while 80% of peridomicile infestations for both triatomine species were in houses not having a previous infestation. New or reinfestation of households did not occur consistent with a sylvan source, and unconstructed lots were not a significant source of bugs. Houses with persistent peridomicile infestation did represent a significant risk for surrounding uninfested houses by cluster analysis (P < 0.05). Along with the increased prevalence of T. cruzi infection after intervention, the data indicate that a sylvan reservoir source, probably peridomicile small rodent nests, represent the major risk factor for persistent and new infestations.

Studies on the spatial distribution of anopheline mosquito larvae were conducted in 302 villages over two transmission seasons in Eritrea. Additional longitudinal studies were also conducted at eight villages over a 24-mo period to determine the seasonal variation in anopheline larval densities. Eight anopheline species were identified with Anopheles arabiensis predominating in most of the habitats. Other species collected included: An. cinereus, An. pretoriensis, An. d’thali, An. funestus, An. squamosus, An. adenensis, and An. demeilloni. An. arabiensis was found in five of the six aquatic habitats found positive for anopheline larvae during the survey. Anopheles larvae were sampled predominantly from stream edges and streambed pools, with samples from this habitat type representing 91.2% (n = 9481) of the total anopheline larval collection in the spatial distribution survey. Other important anopheline habitats included rain pools, ponds, dams, swamps, and drainage channels at communal water supply points. Anopheline larvae were abundant in habitats that were shallow, slow flowing and had clear water. The presence of vegetation, intensity of shade, and permanence of aquatic habitats were not significant determinants of larval distribution and abundance. Larval density was positively correlated with water temperature. Larval abundance increased during the wet season and decreased in the dry season but the timing of peak densities was variable among habitat types and zones. Anopheline larvae were collected all year round with the dry season larval production restricted mainly to artificial aquatic habitats such as drainage channels at communal water supply points. This study provides important information on seasonal patterns of anopheline larval production and larval habitat diversity on a countrywide scale that will be useful in guiding larval control operations in Eritrea.

A field evaluation of a new area repellent system, Thermacell Mosquito Repellent (TMR, cis-trans allethrin), was conducted against phlebotomine sand flies and mosquitoes in Cunpolat village, Sanlıurfa Province, in southeastern Anatolia, Turkey, an area historically endemic for cutaneous leishmaniasis and high sand fly populations. The objective of this study was to determine the efficacy, duration of protection, and spatial characteristics of protection (downwind distance from point of release), of the TMR. Twelve adult volunteers (nine in the treatment and three controls) made collections from ankle to knee for 25 min every hour from 2100 to 0300 on six consecutive nights in August 2002. Treatment consisted of placing a TMR unit at the middle of the village and then placing human bait collectors at 2.3, 4.6, and 7.6 m away from the repellent unit. Results from the field tests showed highly significant protection provided by the TMR from attack by Phlebotomus papatasi (Scopoli) (P < 0.001) and Ochlerotatus caspius (Pallas) (P < 0.001) for up to 4 h postapplication. In the six nights that tests were done, a total of 949 sand flies and 1095 mosquitoes were collected from the untreated control sites. Only 86 sand flies and 83 mosquitoes were collected at all distances from the places treated with TMR. These results indicated that reduction in sand fly and mosquito biting rates in treated groups ranged from 87.5 to 97.7% (mean protection 92%) and 90.2–97.4% (mean protection 93%), respectively. The percentage reduction values were maintained above 90.0% for 6 h of the assessment period. Overall, the number of bites by the cutaneous leishmaniasis vector Ph. papatasi and also Oc. caspius was reduced >11-fold and 13-fold, respectively, by the TMR.

The effectiveness and residual activities of permethrin-impregnated military battle dress uniforms were evaluated by comparing a new company-manufactured ready-to-use polymer-coating method with two “dipping methods” that are currently used to treat uniforms. Residual permethrin amounts and remaining contact toxicities on treated fabrics before and after up to 100 launderings were tested against Aedes aegypti (L.), Ixodes ricinus (L.), and Lepisma saccharina (L.). The residual amount of permethrin was considerably higher with the polymer-coating method: 280 mg a.i./m² after 100 launderings, compared with 16 and 11 mg a.i./m², respectively, obtained when using the two dipping methods. Hard ticks were most susceptible to the new polymer-coating method, resulting in prelaundering 100% knockdown times of 7.0 ± 0.9 min, whereas equivalent times for the dipping methods were 7.9 ± 0.35 min and 8.0 ± 0.54 min, respectively. After 100 launderings, 100% knockdown of I. ricinus nymphs was reached at 15.2 ± 1.04 min using the polymer-coating method, compared with 178.8 ± 24.7 min and 231 ± 53.6 min, respectively, using the dipping methods. Similar results were obtained for Ae. aegypti and L. saccharina, indicating that the polymer-coating method is more effective and efficient when compared with the dipping methods.

A field survey was conducted in 2001 to evaluate resistance to pyrethroid and organophosphate (OP) insecticides on horn flies, Hematobia irritans irritans (L.), from seven ranches in the state of Tamaulipas, Mexico, and from three locations in central Texas. Filter papers impregnated with either technical permethrin or diazinon were used to measure the levels of resistance to pyrethroids and OPs. A multiplex polymerase chain reaction (PCR) assay was used on individual horn flies from these field populations to detect the presence of the kdr and super-kdr alleles associated with pyrethroid resistance, and a mutated αE7 esterase allele associated with OP resistance. Relative to a susceptible laboratory (Kerrville) strain, horn flies from Mexico exhibited 5.1- to 28.3-fold resistance to permethrin at the LC₅₀, and 23.8- to 136-fold resistance at the LC₉₀. Horn flies from Texas ranches exhibited only two- to five-fold resistance. All field populations of the horn fly were highly susceptible to diazinon, and no mutant αE7 esterase alleles were detected. The super-kdr allele was found only in a single fly from a ranch in Mexico. Results of PCR assays showed that the kdr allele was present at various frequencies in field populations of horn flies. A gender-related bias in distribution of kdr genotypes was found in horn flies from Mexico, but not in horn flies from Texas. The overall kdr allelic frequencies in horn flies from Mexico were 23.2–37.8% higher in females than in males. Regression analysis revealed a significant correlation between kdr allelic frequencies and the levels of knockdown resistance to permethrin among the horn fly populations studied. The results validate the role of the PCR-based molecular assay as a diagnostic tool in monitoring resistance to pyrethroids and also provide useful information on population genetics of horn fly resistance to pyrethroids and OPs.

Australian Aedes aegypti (L.) mosquitoes colonized from the Torres Strait and three mainland localities (Charters Towers, Townsville, and Cairns) were fed on blood suspensions containing dengue virus type 2 (DEN-2) or dengue virus type 4 (DEN-4). Variation was found in oral susceptibility to DEN-2 (59–99% infection) and DEN-4 (28–79% infection) among Ae. aegypti assayed for virus at 8, 12, 16, or 20 d after ingestion of infected blood. Torres Strait Ae. aegypti were the most susceptible to DEN-2 and were significantly more efficient in transmission to capillary tube at 16 d (76% transmission) than mainland Ae. aegypti populations (20–28% transmission). Torres Strait Ae. aegypti were also the most susceptible to DEN-4, although transmission did not vary significantly from mainland populations at 16 d (12% compared with 0–4%) or 20 d (16% compared with 4–16%). Disseminated infection (i.e., leg infection) with either DEN-2 or DEN-4 was not an accurate predictor of transmission potential. This study demonstrates differences among Australian Ae. aegypti populations in vector competence for DEN-2 and DEN-4. Torres Strait Ae. aegypti were more frequently infected and able to transmit DEN-2 at higher rates than mainland populations. These data indicate that the Torres Strait region is potentially more receptive to dengue transmission than mainland localities, a finding discussed with respect to past outbreaks.

Vesicular stomatitis (VS) is an economically devastating disease of livestock in the Americas. Despite strong circumstantial evidence for the role of arthropods in epizootics, no hematophagous vector explains the field evidence. Based on the spatiotemporal association of grasshopper outbreaks and VS epizootics, we investigated the potential role of these insects as vectors and reservoirs of the disease. The critical steps in the grasshopper–bovine transmission cycle were demonstrated, including 1) 62% of grasshoppers [Melanoplus sanguinipes (F.)] fed vesicular stomatitis virus (VSV) from cell culture became infected, with titers reaching 40,000 times the inoculative dose; 2) 40% of grasshoppers that cannibalized VSV-infected grasshopper cadavers became infected, amplifying virus up to 1,000-fold; 3) one of three cattle consuming VSV-infected grasshopper cadavers contracted typical VS and shed virus in saliva; and 4) 15% of grasshoppers became infected when fed saliva from this infected cow. The ecological conditions and biological processes necessary for these transmissions to occur are present throughout much of the Americas. Field studies will be required to show these findings are relevant to the natural epidemiology of VSV.

The principal vector of Borrelia burgdorferi, the Lyme borreliosis spirochete, in the Northeast and Midwestern regions of the United States is the blacklegged tick Ixodes scapularis. Because of a favorable environment, I. scapularis is also plentiful in the South; however, a correlation with Lyme borreliosis cases does not exist in this region of the United States. Concern existed that something intrinsic to ticks found in Louisiana could mitigate their ability to transmit B. burgdorferi. Therefore, we set out to assess the ability of I. scapularis ticks from Louisiana to become infected with and transmit B. burgdorferi using mice as hosts. In the laboratory, mating adult female ticks collected in southeastern Louisiana were fed on the ears of rabbits. After oviposition and egg hatching, the resulting larvae were fed on mice that had been needle-inoculated with two different strains of B. burgdorferi sensu stricto, B31 and JD1. Larvae were found to be positive for spirochetes. Additional fed larvae were allowed to molt into the nymphal stage. Flat nymphs remained infected with B. burgdorferi. Infected nymphs were allowed to feed on naïve mice, all of which became infected as shown by culture of ear biopsy specimens. Naïve larvae were then fed on these same mice to assess transmissibility. The resulting engorged larvae harbored spirochetes. We have demonstrated that the I. scapularis ticks found in Louisiana are fully competent to carry and transmit B. burgdorferi infection.

A total of 27 bird species from the San Joaquin and Coachella valleys of California were inoculated subcutaneously with sympatric strains of western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses. Overall, 133 of 164 birds inoculated with WEE virus developed a viremia detected by plaque assay; significantly greater than 72 of 163 birds inoculated with SLE virus. Host competence was calculated as the average number of days that each avian species had a viremia ≥2 log₁₀ plaque-forming units per 0.1 ml, the threshold for infecting susceptible Culex tarsalis Coquillett, the primary vector of these viruses in California. Eleven of 20 species inoculated with WEE virus had a value ≥1 and were considered to be competent hosts, whereas only six of 22 species inoculated with SLE virus had a value ≥1. Overall, 133 of 164 birds inoculated with WEE virus and 105 of 163 inoculated with SLE virus produced antibody detectable by enzyme immunoassay and/or plaque reduction neutralization test. Six birds infected with WEE virus (one house finch, three mourning doves, one Brewer’s sparrow, and one white-crowned sparrow) and nine birds infected with SLE virus (two house finches, three white-crowned sparrows, one song sparrow, two Western scrub-jays, and one orange crowned warbler) contained viral RNA detected by reverse transcription-polymerase chain reaction at necropsy >6 wk postinoculation; infectious WEE and SLE viruses were only recovered from three mourning doves and an orange-crowned warbler, respectively, after blind passage in mosquito cells. Our study indicated that birds with elevated field antibody prevalence rates may not be the most competent hosts for encephalitis viruses and that relatively few birds developed chronic infections that could be important in virus persistence and dispersal.

We reported on the hairy maggot of Chrysomya villeneuvi Patton, collected from a human corpse in Thailand. Although the general morphology of the third instar closely resembled the more common hairy maggot blow fly, Chrysomya rufifacies (Macquart), the spines along the tubercles of each body segment could be used as a feature to distinguish between these species, with those of C. villeneuvi bearing sharp-ended spines that encircle the entire tubercle. Not only has the resemblance of a hairy appearance between C. villeneuvi and C. rufifacies larvae been documented but also their similarity in predacious feeding behavior. The differentiation between these two species is necessary for post-mortem interval estimation in the corpse.

Pyrethroid-treated nets are an efficient tool for reducing malaria transmission and morbidity. The recent evolution of pyrethroid resistance in several Anopheles species represents a major threat for the future success of roll back malaria in Africa. The possible use of nonpyrethroid insecticides, such as carbamates, on nets is a promising alternative solution because these insecticides are effective against susceptible and pyrethroid-resistant populations of Anopheles and Culex mosquitoes. Unfortunately, carbamate resistance as a result of insensitive acetylcholinesterase has recently been detected in Anopheles gambiae s.s. populations from Côte d’Ivoire. Using biochemical assays on surviving Anopheles mosquitoes from an experimental hut trial, we showed evidence for selection for an insensitive acetylcholinesterase mechanism by carbamate impregnated bednets. However, no such selection has been found with nets treated with pyrethroid alone or pyrethroid/carbamate “two-in-one”-treated nets. Because pyrethroid-impregnated nets were suspected to select for the Kdr mutation in An. gambiae, we propose that use of two-in-one nets could be a promising alternative strategy for the management of insecticide resistance in malaria vectors.

Although Panstrongylus lutzi (Neiva and Pinto) is currently the fifth most frequent species of Triatominae captured in artificial structures in Brazil, its silvatic habitat remains unknown. A survey of its natural ecotopes was performed in an area of Bahia State. P. lutzi nymphal instars and adults were detected in burrows of Dasypodidae. Silvatic habitat of four other endemic triatomine species of the caatinga (Triatoma pseudomaculata Correa and Espinola, Triatoma brasiliensis Neiva, Rhodnius neglectus Lent, and Psammolestes tertius Lent and Jurberg) was also recorded.

Trypsin activity increases in the midgut of Anopheles aquasalis, Anopheles albitarsis, and Anopheles darlingi after a bloodmeal. The activity returns to basal levels at the time the blood is completely digested. Affinity chromatography, reversed-phase high performance liquid chromatography (HPLC), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were used to sequentially purify the mosquito trypsins found in the midguts at 24 h after feeding. Amino-terminal sequencing of the purified trypsins showed the occurrence of two distinct trypsins in the midgut of each of the mosquitoes studied. The sequences obtained are similar to those of the trypsins of other hematophagous insects.

The Mexican free-tailed bat, Tadarida brasiliensis mexicana, is one of the most widely distributed bats, and its range includes the whole Mexican territory. Ectoparasites of this bat have been the subject of isolated reports, but no studies of its community ecology have been conducted. The acarine infracommunities associated with this bat were analyzed, comparing bat populations from three arid regions of Mexico: an abandoned factory in Nombre de Dios, Durango; a cave in Santiago, Nuevo León; and a church in Concepción del Oro, Zacatecas. The acarine infracommunity in Nuevo León’s bats exhibited the highest levels of diversity as reflected by a higher richness, a lower dominance, and a moderate and relatively homogeneous abundance in this locality in relation to the other two. This pattern is influenced by stable cave conditions relative to artificial habitats. Notwithstanding, further studies are required to determine whether or not different habitat conditions are a primary factor in the process of structuring the acari infracommunities.

It has long been assumed that Ehrlichia chaffeensis (Anderson, Dawson & Wilson), is not transmitted transovarially in the lone star tick vector Amblyomma americanum (L.). To test this hypothesis, three beagle dogs, Canis familiaris (L.) (Carnivora: Canidae), were subcutaneously infected with E. chaffeensis (Arkansas strain). Uninfected nymphal lone star ticks were placed on the infected dogs and allowed to feed to repletion. These nymphal ticks were allowed to molt, and five of five adult female ticks sampled were confirmed to be infected by polymerase chain reaction (PCR). Forty infected adult ticks, the majority of which were female with several males included to stimulate feeding, were then placed on two uninfected dogs. Fourteen females were removed early and the rest were allowed to feed to repletion. After feeding to repletion, the six remaining females detached and two of these females were tested preoviposition, whereas the remaining four were allowed to lay eggs. All six of these fully engorged females tested negative by PCR. The egg clutches laid by four engorged adult females, and the larvae that hatched from these eggs along with larvae from a previously untested egg clutch, were shown to be uninfected by PCR. This seems to support the long-held assumption of lack of transovarial transmission. Also of interest, we found that these PCR-confirmed infected adult ticks reared in the laboratory did not transmit E. chaffeensis to uninfected dogs.