This study examined the ability of ticks to maintain multiple species of spotted fever group rickettsiae via transovarial transmission. Using a capillary feeding method, previously established Rickettsia montana- and Rickettsia rhipicephali-infected cohorts of Dermacentor variabilis (Say) were exposed to R. rhipicephali and R. montana, respectively, in two reciprocal challenge experiments. Eggs collected from individual females, for two successive generations, of each cohort were assessed for rickettsial infection by polymerase chain reaction for each challenge experiment. Assessment of the eggs from challenged ticks identified that both R. montana- and R. rhipicephali-infected ticks were refractory to their respective challenge rickettsiae. The prechallenged infection rate for both F1 and F2 generations (100%) of the R. montana-infected cohort was resistant to transovarial transmission of the second rickettsia species, and only R. montana was detected in the eggs of F1 = (50%) and F2 = (74%) challenged females. The R. rhipicephali-infected cohort maintained a lower level of infection (20%) in the population and did not transovarially transmit the challenge species, however, detectable levels of infection were lost after the first generation. Second-generation ticks, no longer infected with R. rhipicephali, became susceptible to infection with R. montana and female ticks (≈4%) were able to transmit R. montana to their progeny. The resistance of the ovaries to co-infection and apparent host-specific nature of infection suggests that rickettsial infection of tick ovaries may alter the molecular expression of the oocytes so as to preclude secondary infection with other rickettsiae.

The tick Amblyomma humerale Koch is endemic to South America. All host records refer to the adult stage parasitizing tortoises, mostly yellow-footed tortoise, Geochelone denticulata (L.), and red-footed tortoise, Geochelone carbonaria (Spix). The current study reports the presence of A. humerale in the state of Rondônia, Brazil. A total of 215 adult ticks (201 males, 14 females) was collected from six G. denticulata in an Indian reserve and nine Geochelone sp. in rural Monte Negro County, giving an overall mean infestation of 14.3 ± 12.0 (range: 2–44) ticks per tortoise. Male ticks always outnumbered females on the host and nine tortoises had only male ticks. Male ticks were mostly attached in clusters on the ventral sides of the carapace near the anterior and posterior margins, and more rarely on the outer margin of the plastron. All females were found attached to the tortoise skin, at different sites such as head, neck, shoulders or legs. Male ticks were rarely observed attached to the body skin. Seven engorged nymphs collected on small vertebrates from Monte Negro County molted to adults of A. humerale. This included one nymph each on the seven-colored lizard, Plica plica (L.), green tree climber, Plica umbra (L.), and wide-foraging lizard, Kentropyx calcarata Spix, three nymphs on the common opossum, Didelphis marsupialis L., and one nymph on the silky anteater, Cyclopes didactylus L. These constitute the first host records for the immature stages of the tick A. humerale.

Microtus californicus (Peale, 1848) were live trapped or retrapped 887 times, and fleas were collected over a 2.5-yr period in the San Francisco Watershed and Wildlife Refuge. Also, 179 M. californicus nests were collected monthly with observations to identify the environment of fleas. The ratio of the mean number of fleas per nest to the mean number collected on voles was 4.7:1 for Malaraeus telchinus (Rothschild, 1905), 13:1 for Hystrichopsylla occidentalis linsdalei Holland, 1957, 9:1 for Atyphloceras multidentatus multidentatus (C. Fox, 1909), and 76:1 for Catallagia wymani (C. Fox, 1909). The proportion of each flea species per nest to those per host was not closely associated seasonally or spatially. The average nest contained 37.5% moisture content in relation to its total weight and ranged between 3 and 92%. No relationship was observed between relative humidity of air within nests and flea number, but a significant relationship existed between the moisture of nesting materials and flea number. Malaraeus telchinus and A. m. multidentatus were collected in greatest numbers from nests having 30–39% moisture content by weight, and H. o. linsdalei and C. wymani were most numerous in nests that had 40–49% moisture content. Catallagia wymani had the greatest tolerance for high moisture and was severely affected by lack of moisture and nearly absent in drier nests. No ectoparasites were collected from nests that had <12% moisture content, and nests with >50% moisture content had few fleas. A static concept of nest fleas and host fleas as suggested by averages and often used in literature is questionable. In seasonal comparison of populations of fleas on hosts and in nests, M. telchinus and H. o. linsdalei reversed so that more of the flea population was on the host than in the nest for a short time during fall.

Cyanobacteria associated with Anopheles albimanus Wiedemann larval habitats from southern Chiapas, Mexico, were isolated and identified from water samples and larval midguts using selective medium BG-11. Larval breeding sites were classified according to their hydrology and dominant vegetation. Cyanobacteria isolated in water samples were recorded and analyzed according to hydrological and vegetation habitat breeding types, and mosquito larval abundance. In total, 19 cyanobacteria species were isolated from water samples. Overall, the most frequently isolated cyanobacterial taxa were Phormidium sp., Oscillatoria sp., Aphanocapsa cf. littoralis, Lyngbya lutea, P. animalis, and Anabaena cf. spiroides. Cyanobacteria were especially abundant in estuaries, irrigation canals, river margins and mangrove lagoons, and more cyanobacteria were isolated from Brachiaria mutica, Ceratophyllum demersum, and Hymenachne amplexicaulis habitats. Cyanobacteria were found in habitats with low to high An. albimanus larval abundance, but Aphanocapsa cf. littoralis was associated with habitats of low larval abundance. No correlation was found between water chemistry parameters and the presence of cyanobacteria, however, water temperature (29.2–29.4°C) and phosphate concentration (79.8–136.5 ppb) were associated with medium and high mosquito larvae abundance. In An. albimanus larval midguts, only six species of cyanobacteria were isolated, the majority being from the most abundant cyanobacteria in water samples.

Since 1988 malaria epidemics have occurred in multiple sites in western Kenya highlands. Climatic variability has been associated with some of the recent epidemics. We examined influences of climatic factors on the distribution and abundance of three malaria vector species, Anopheles gambiae, Anopheles arabiensis, and Anopheles funestus in western Kenya and in the Great Rift Valley. Mosquito samples were collected from the lowland and highland areas with various climatic conditions. The three vector species were abundant in the lower part of western Kenya. An. arabiensis was not found in the areas above 1,400 m elevation in western Kenya. Although An. gambiae and An. funestus were found in the sites above 1,700 m in western Kenya, their densities were <1 per house. In the Great Rift Valley, An. gambiae was not recorded. An. funestus was more widely distributed than the other two species. A stepwise multiple regression analysis found that moisture index was the most important variable in shaping species composition of the An. gambiae complex. Relative abundance of An. gambiae was positively associated with moisture index, suggesting that An. gambiae is more adapted to moist climate. Seasonal differences in species composition were significant in western Kenya, and the proportion of An. funestus was higher in the dry season than the rainy season. Influence of temperature on vector density was significant for all three species. These results imply that climate changes alter the distribution and abundance of malaria vectors in future.

We measured three components of the behavioral activity of blacklegged tick (Ixodes scapularis Say) nymphs under controlled conditions of daylength, temperature, and relative humidity in the laboratory. Temperature and relative humidity were experimentally manipulated among replicated treatment groups in two experiments. Humidity treatment had a significant effect on mean questing height, which was greater at 100% RH than at any lower humidity (P < 0.01), but it had no effect on mean distance moved between observations or the mean percentage of time in questing posture. Temperature had no effect on mean questing height, but significantly affected mean distance moved (P < 0.01) and the percentage of time in questing posture (P < 0.001). Mean distance moved and percentage of time in questing posture were both greater at 25°C than at higher or lower temperatures. A mechanistic understanding of the factors affecting tick behavior is likely to be useful for interpreting field data, designing field studies, and predicting risk of exposure to tick-borne pathogens.

Questing female blacklegged ticks, Ixodes scapularis, Say in Massachusetts rarely bear more than one endospermatophore in their reproductive tracts. We evaluated the cause of this nonrandom distribution by examining the stability of endospermatophore retention in females and the effect of prior insemination of females on the copulatory behavior of male ticks. Endospermatophores were retained without degradation in unfed female ticks for >1 yr at 5°C and for at least 4 mo at 21°C. Males were much more likely to abort preprandial (before feeding) copulations without inseminating females bearing endospermatophores. This remating inhibition activity persisted in unfed females for at least 2 mo after insemination. Perprandial (during feedng) copulations were less restrictive, particularly when females became partially engorged. Males were more likely to remain in copula with previously inseminated females that were engorged, but generally did not transfer spermatophores to them until their fifth day of attachment to a rabbit. Little inhibitory activity was evident during the final, rapid engorgement phase of feeding. Thus, remating inhibition appears to degrade as feeding progresses. In summary, an unknown factor associated with the previous insemination of females inhibits subsequent spermatophore transfer by causing mating pairs to interrupt copulation soon after initiation. Remating inhibition is strongest in unfed ticks and becomes less apparent as females become engorged.

A field population of Culex (Culex) nigripalpus Theobald from Vero Beach, FL, sampled monthly over a period of 24 mo, a colony sample and 10 geographic samples were analyzed for genetic variation at 14 enzyme loci using polyacrylamide gel electrophoresis. The Cx. nigripalpus colony sample showed significantly lower genetic variation than the field-collected samples, measured by mean number of alleles per locus (colony 1.4 ± 0.1 versus field 2.1 ± 0.22), percentage of polymorphic loci (colony 35.7% versus field 54.8 ± 7.7%), but mean observed heterozygosity (H_o = colony 0.16 ± 0.07 versus field 0.17 ± 0.03) and mean Hardy–Weinberg expected heterozygosity (H_e = colony 0.14 ± 0.06 versus field 0.18 ± 0.02) did not differ significantly. Three of the 14 loci (Aldox, Gpd, and Gpi) from the Vero Beach field samples showed distinct temporal patterns in the frequency of the most common allele. Higher mean observed heterozygosity (H_o) occurred during months following high rainfall in the Vero Beach field samples than during months following low rainfall. The average Nm value of 3.6 indicated high gene flow among the temporally distributed samples of the Vero Beach population. Genetic variability values between geographic samples from Panhandle, FL and south Florida were not significant. Gene flow estimates based on F_ST = 0.039 provided a Nm of 6.2 indicating high levels of gene flow among the geographic samples of Cx. nigripalpus. The average Nei’s and modified Rogers’ genetic distances among the 10 populations were 0.009 ± 0.001 and 0.081 ± 0.004, respectively. The cluster analysis did not suggest geographic clustering. Because Cx. nigripalpus is the vector of St. Louis encephalitis (SLE) in Florida, temporal and geographic genetic variation in this species is discussed in relation to the seasonal and geographic SLE virus activity in Florida.

The Neotropical malaria vector Anopheles aquasalis Curry is distributed predominantly along the Atlantic and Pacific Coasts because of its tolerance for breeding in salt water. We tested the hypothesis that the freshwater Amazon River acts as a barrier to gene flow in northeastern Brazil, by examining variation at a 588-nucleotide fragment of the mitochondrial cytochrome oxidase I gene from five populations. We identified 15 haplotypes of which 5 were shared both (1) between sample localities and (2) across the Amazon River Delta. Sequence divergence ranged from 0.0017–0.0272 (average = 0.0137). Estimates of genetic subdivision based on the presence of the Amazon River were greatest within localities (Φ = 0.029) and among regions (Φ = 0.018), followed by among localities (Φ = 0.011), but none were significant. Parsimony, neighbor-joining, and Nested Clade Analyses were used to estimate relationships among populations and infer evolutionary processes. Two phylogenetically distinct clusters of populations were moderately supported by parsimony. Neighbor-joining trees were poorly resolved, thus providing no geographical resolution and no support for the Amazon River as a barrier to migration. Phylogeographic structure as detected by the Nested Clade Analysis was consistent with restricted gene flow coupled with isolation by distance. Taken together, these analyses suggest that the localities within this region of northeastern Brazil constitute a single large population of An. aquasalis that spans the Amazon Delta.

The knockdown resistance (kdr) mutation in the voltage-gated sodium channel gene (VGSCG), an important resistance mechanism against pyrethroids, was studied in Anopheles sacharovi Favre. It was found that the specific primers Agdl and Agd2 used for polymerase chain reaction (PCR) amplification of Anopheles gambiae Giles VGSCG also amplified this genomic region in An. sacharovi. Comparison of the IIs4–IIs6 domain segments of the gene indicated 70% nucleotides common to both species and a genetic distance of 0.255 between them. Four different samples of pyrethroid-resistant An. sacharovi produced three types of amino acid, serine (TCG), leucine (TTG), and phenylalanine (TTT) at the kdr mutation point, whereas only two kdr mutations, leucine to phenylalanine and leucine to serine, occur in An. gambiae.

The role of water balance capabilities of fleas was examined in desert habitats. The fleas studied were Xenopsylla ramesis Rothschild and Xenopsylla conformis Wagner. Both fleas occur on Sundevall’s jird, Meriones crassus, in the Negev Highlands of Israel but in different macro- and microhabitats. Because M. crassus occurs in several habitats of the highlands, it was used as a model for investigating the effect of habitat parameters on species composition of fleas within a host species. Water balance parameters investigated were the range of humidities over which active water uptake occurs in the larvae and prepupae of X. ramesis and X. conformis. Critical equilibrium humidity estimates were close to 65% RH for larvae and prepupae of both species. Water loss rates were determined for each life stage, except eggs, and represented water loss from cuticular, respiratory, and other body openings) under conditions of little or no bulk air movement. When converted to a proportional rate (1.44–2.37% mass loss h⁻¹) water loss rates did not differ significantly between stages or species. Thus, geographic separation of X. ramesis and X. conformis could not be explained by any difference in water uptake capabilities or water loss rates. Other factors that may be important include interspecific competition for resource availability among larval fleas and effect of soil texture on cocoon construction.

A sample of Aedes aegypti (L.) from Santiago de Cuba, Cuba, with a high level of temephos resistance (19.58× at the 50% lethal concentration [LC₅₀]), was subjected to temephos selection to evaluate the utility of this organophosphate insecticide for mosquito control. High resistance developed after six generations of selection (200.00×). Little or no cross-resistance was observed to the organophosphates, malathion and fenitrothion, but high cross-resistance was observed for the pyrethroid deltamethrin (337.5×) and the organophosphate fenthion (12.74×). Synergism tests implicated detoxifying esterases in temephos and fenthion resistance and deltamethrin resistance was associated with a cytochrome P450 monooxygenasa. Biochemical tests, polyacrylamide gel electrophoresis (PAGE), and inhibition studies confirmed the presence of elevated esterase activity associated with temephos resistance. Pyrethroid resistance could be associated with a glutathione-S-transferase mechanism but not the esterases. The cross-resistance to deltamethrin from temephos selection could limit the use of both insecticides for Ae. aegypti control.

The efficacy of a photostable formulation of methoprene and two photostable juvenoids, fenoxycarb and pyriproxyfen, and their residual activity in inhibiting the emergence of adult cat fleas, Ctenocephalides felis (Bouché), was studied in topsoil. Nursery pots composed of clay, peat, and plastic, and wooden flats were used to hold soil samples. Treated soil samples were exposed to sunlight during the 63-d study period. Methoprene was as effective as fenoxycarb and pyriproxyfen against cat fleas for up to 42 d in clay, peat, and plastic pots at a concentration of 64.56 mg (AI)/m² (6 mg [AI]/ft²), but its activity declined significantly thereafter. In contrast, fenoxycarb and pyriproxyfen showed strong residual activity for the entire 63 d. The activity of methoprene declined even more rapidly over time in wooden flats, while at the same concentrations the other two juvenoids showed significant residual activity for 63 d. Clay, peat, and plastic pots were therefore considered to be equally effective for evaluating the outdoor efficacy of juvenoids in comparison to the wooden flats. However, results obtained with wooden flats may be more realistic when testing residual activity of volatile chemicals such as methoprene. Fenoxycarb and pyriproxyfen showed strong efficacy and residual activity at concentrations of 8.07, 16.14, and 32.28 mg (AI)/m², whereas methoprene did not cause a significant reduction of adult emergence at levels below 64.56 mg (AI)/m². LC₅₀ values for methoprene, fenoxycarb, and pyriproxyfen needed for preventing flea emergence when applied to topsoil were estimated to be 0.643, 0.031, and 0.028 ppm, respectively.

IR3535, KBR3023, para-menthane-3,8-diol (PMD), and deet were evaluated in controlled studies with human subjects (n = 5) for repellency to black salt marsh mosquitoes (Ochlerotatus taeniorhynchus Wiedemann), in the Everglades National Park, FL. In tests of 6-h duration, with an average mosquito biting pressure on exposed forearm skin of 19.5 (±13.7) bites per minute, the mean percent repellencies (SE) for IR3535, KBR3023, PMD, and deet was 88.6 (3.2), 97.5 (1.7), 89.2 (2.9), and 94.8 (2.5), respectively. Mean complete protection times (SE) for IR3535, KBR3023, PMD, and deet were 3.0 (1.0), 5.4 (0.6), 3.8 (1.4), and 5.6 (0.5) h, respectively. Untreated (ethanol) controls provided 0% repellency. When mosquito biting rates on the untreated forearm skin of repellent-treated subjects were compared with biting rates on the forearm skin of control subjects, the former were 23%–40% lower early in tests and as much as 22% higher late in tests. These differences cast doubt on the technical merit of test designs comprising evaluation of more than one repellent at a time on the same human subject while underscoring the importance of untreated subjects as negative controls in field repellent bioassays.

The effect of salivary gland extract of the stable fly, Stomoxys calcitrans (L.), on bovine lymphocyte proliferation was determined, and antibody reactivity to salivary gland proteins was characterized in cattle exposed to stable flies. Salivary glands were dissected from male and female flies (4–8 d after eclosion), and protein extracts were made by freeze–thaw cycles. Salivary gland extract (SGE, 1 and 5 μg) significantly inhibited mitogen-driven proliferation of bovine lymphocytes, compared with 1 and 5 μg of identically prepared midgut extract (ANOVA, P < 0.05). Phytohemagglutinin A (PHA) stimulated lymphocyte responses were suppressed by 61.7 and 79.5% (mean values) with 1 and 5 μg of SGE, whereas concanvalin A (Con A) stimulated responses were suppressed by 62.9 and 77.1% (1 and 5 μg). In contrast, midgut extract (1 and 5 μg) minimally suppressed PHA (12.7% ± 12.6 and 18.7% ± 15.5) and Con A-driven responses (13.8% ± 20.5 and 24.6% ± 14.9), respectively. Viability studies using propidium iodide and flow cytometry demonstrated that SGE was not cytotoxic. Two-color immunofluorescence studies identified T and B lymphocytes as the nonviable cells in the cultures. Western blot analysis of serum collected from five dairy cows during periods of low and high fly exposure identified an immunodominant 27 kDa protein among the salivary gland proteins. These results indicate that exposure of cattle to stable fly saliva during blood feeding results in an antibody response to salivary proteins and that the saliva has a potential to modulate T lymphocyte function.

Black flies (Simulium spp.) are intermediate hosts and vectors of parasitic nematodes belonging to the genus Onchocerca (Filarioidea: Onchocercidae). Infection and subsequent transmission of infective third-stage larvae occur at the vertebrate host–skin interface. Experimental evidence presented here demonstrates that Onchocerca lienalis Stiles microfilariae orient to one or more components (microfilarial orientation factor[s]; MOF) in black fly saliva. MOFs may serve as a means for microfilariae to find and infect black flies during the act of blood-feeding. Directed movement through the host’s skin to the bite site is necessary because Onchocerca spp. microfilariae do not circulate in the blood. The substance directing microfilarial orientation appears to be a salivary protein, but it is not the Simulium vittatum Zetterstedt erythema protein (SVEP) described from New World Simulium spp. These results support earlier field observations that associated increased numbers of cutaneous microfilariae with black fly feeding and indicate that a fundamental molecular mechanism linked to vector saliva may be key for the maintenance of the life cycle of Onchocerca spp. Salivary molecules that induce orientation of microfilariae to the bite site are potential targets for use in transmission-blocking vaccines to uncouple this primary vector infection step.

Two out of three pools of cat fleas, Ctenocephalides felis (Bouché), that were fed Bartonella henselae-positive cat blood for 3 d and then bovine blood for 3 d, were polymerase chain reaction (PCR) positive for B. henselae. In a second experiment, three cats were inoculated with a streptomycin-resistant strain of B. henselae. After the cats were inoculated, caged cat fleas were fed on the cats during three different periods, and then pooled and transferred to noninfected recipient cats. In the first trial, the bacteria in the flea feces were below level of detection when the fleas were transferred from the infected cats to the recipient cat. After the fleas had fed on the recipient cat for 6 d, a bacteria level of 4.00 × 10³ CFU/mg was detected in the flea feces. Subsequently, the bacteria level increased for 4 d and then declined. In another experiment, the bacteria level in the flea feces was 1.80 × 10³ CFU/mg at 2 h after collection and 3.33 × 10² CFU/mg at 72 h after collection. These data indicated that this strain of B. henselae can persist in flea feces in the environment for at least 3 d, and that B. henselae can multiply in the cat flea.

The seasonal occurrence and abundance of a newly introduced mosquito in the United States, Ochlerotatus (Finlaya) japonicus (Theobald), are reported for Westchester and Putnam Counties in southern New York State. Adult mosquitoes were sampled at 39 sites distributed throughout the two counties. CDC (Centers for Disease Control and Prevention) light traps (2,107 trap nights) and gravid traps (1,813 trap nights) were used to collect a total of 44,428 mosquitoes from May through October 2000. Oc. japonicus was found at 97.4% of sites sampled and accounted for 9.8% of all specimens collected. Oc. japonicus was recovered from 1.5% (n = 326) of the light trap collections and 18.1% (n = 4,026) of the gravid trap collections. Although gravid traps collected significantly more specimens than light traps, the seasonal activity patterns measured by each trap type were congruent. In all, 30 mosquito species were collected. Unlike other Ochlerotatus or Aedes species, Oc. japonicus was collected throughout the study, indicating a broad seasonal activity period. There was significant regional variation in Oc. japonicus abundance, with higher trap densities occurring in the northern-most trapping sites. This study demonstrates that Oc. japonicus is established in southern New York State.

Mark-release-recapture experiments were conducted to determine the duration of the gonotrophic cycle of Anopheles albitarsis s.l. in Ribeira Valley, State of Sao Paulo, Brazil. Separate experiments with females collected from the field were followed under laboratory conditions. A mean of 2.4 d was characteristic for the gonotrophic cycle for wild-caught females, whereas 4.4 d was characteristic for females in the laboratory conditions.

Adult blowflies, Calliphora vicina Robineau-Desvoidy, are exposed to bacteria-laden decay as adults and larvae. They are protected from infections in such habitats by a family of lytic proteins called Cecropins. In this study, we explore the relationship between the developmental stages of the blowfly and the strength of the immune response when insulted by an endogenous pathogen, Escherichia coli. Our data indicate that the protective function of Cecropin B varies with developmental stage. Pupae that were not fully tanned exhibited the greatest response to an insult by E. coli. The expression of an increased immune response is due in part to an increased concentration of Cecropin B manufactured by this instar.

In a Central Michigan wetland setting, air drawn through a DEET-impregnated screen using an electric fan and projected toward a human subject significantly reduced mosquito orientation by 74%, landing by 75%, and probing by 70%, relative to no applied wind or DEET. The DEET vapor effect was significant as revealed by a statistically significant wind/DEET interaction. The wind speed at the downwind human subject was 0.6 m/s and the DEET vapor concentration was estimated at 2 μg/liter air. We suggest a combination of directed wind and volatile repellent might be developed as a mosquito deterrent strategy for the backyard setting.

The purpose of this study was to conduct a survey for the susceptibility of the horn fly, Hematobia irritans (L.), populations to permethrin on dairy cattle from Aguascalientes, Mexico. Samples of populations of horn flies at 25 dairies were exposed to two discriminating doses (2.5 and 6.0 μg/cm²) on permethrin-treated filter papers and the percentage of mortality was compared with that of a susceptible strain treated with same doses of permethrin. The results show that there was a difference in the mortality from two discriminating doses and the mortality of the susceptible strain. Therefore, horn fly populations at all dairies tested in Aguascalientes, Mexico, were susceptible to permethrin. This insecticide, as well as other pyrethroids, could continue to be used to provide satisfactory control of horn flies in the study region.

Female Anopheles mosquitoes usually mate only once, but mating is seldom seen in small containers containing only one female and male. Therefore, matings are often performed among many adults in large cages or by forced copulation. Isolated-pair mating of Anopheles gambiae G3 strain–derived mosquitoes without forced copulation in small vials is described. We observed that the experimental variables eye color and male number were significant factors in the mating frequency. Females mated more frequently when three males were present over only one male. White-eyed females were more likely to be mated than wild-eyed females, but wild males mated more frequently than did white-eyed males. Experiments were also conducted to determine when mating was occurring by using wild-eye-color mosquitoes in isolated pairs. Almost no matings were observed before day 6 rather than the frequencies typically observed after 1–2 d in standard large-cage matings among large numbers of adults.

Presence of 2,4-dichlorophenol (2,4-DCP) in extracts of fed and nonfed adult female Dermacentor variabilis (Say) by gas chromatography and mass spectroscopy (GC/MS) is reported. 2,4-DCP was detected as part of a mixture with 2,6-dichlorophenol, which is the attractant sex pheromone in this species in a 1:9 ratio, respectively. Extracts did not contain the monochlorinated phenols, 2-chlorophenol and 4-chlorophenol. None of these chlorophenols were detected in eggs. 2,4-DCP is comparable in efficacy to 2,6-DCP as an attractant sex pheromone, prompting attraction, arrestment and feeding posture behavior by fed males. It is also present in the female adult.

During a 6-mo period, 2,055 brown recluse spiders, Loxosceles reclusa Gertsch and Mulaik, were collected in a 19th-century-built, currently occupied home in Lenexa, KS. We conservatively estimate that at least 400 of these spiders were large enough to cause envenomation. Additional collections from more typically infested homes in Missouri and Oklahoma in 2001 yielded 45 and 30 brown recluse spiders, respectively. Despite these infestations, no envenomations of the inhabitants of these three homes occurred. Considering the levels of infestations with no bites in the homes presented here, nonendemic areas in the United States, which typically lack recluse spider populations and have had zero to few verified specimens of the spider, do not have sufficient numbers of brown recluse spiders to make envenomation a likely scenario. Despite this, physicians from nonendemic recluse areas often diagnose brown recluse bites which, therefore, are unlikely to be correct.