Understanding how and why insect numbers fluctuate through time and space has been a central theme in ecological research for more than a century. Life tables have been used to understand temporal and spatial patterns in insect numbers. In this study, we estimated cause-of-death probabilities for phytophagous insects using multiple decrement life tables and the irreplaceable mortality analytic technique. Multiple decrement life tables were created from 73 insect life tables published from 1954 to 2004. Irreplaceable mortality (the portion of mortality that cannot be replaced by another cause) from pathogens, predators, and parasitoids was 8.6 ± 7.2, 7.8 ± 4.9, and 6.2 ± 1.6%, respectively. In contrast, the mean irreplaceable mortality from all non-natural enemy mortality factors (mortality from factors other than natural enemies) was 35.1 ± 4.4%. Irreplaceable mortality from natural enemies was significantly lower compared with non-natural enemy factors. Our results may partially explain cases of unsuccessful efficacy in classical biological control, after successful establishment, by showing low irreplaceable mortality for natural enemies, including 5.2 ± 1.6% for introduced natural enemies. We suggest that the environment (i.e., the degree of environmental stability) influences the magnitude of the irreplaceable mortality from natural enemies. Our results lead to several testable hypotheses and emphasize that it is not possible to estimate the effect of any mortality factor without considering its interaction with competing mortality factors, which has far-reaching consequences for population biology and applied ecology.

Laboratory experiments were conducted to estimate developmental rates and nymphal survival of Aleyrodes proletella Linnaeus (Homoptera: Aleyrodidae) on two broccoli Brassica oleracea L. variety italica Plenck cultivars (Marathon and Agripa) at eight constant temperatures (16, 18, 20, 22,24,26,28, and 30°C). The times required to complete development of egg and first instar decreased with increasing temperature, but the developmental times of second, third, fourth instars, all instars, and egg-adult period were greater at 30°C than at 28°C. The relationships between developmental rate of A. proletella and temperature were slightly influenced by broccoli cultivar. The optimal temperatures and thermal constant as well as the lower and upper thresholds of development for all immature stages were estimated by fitting the observed developmental rates versus temperature with a nonlinear model and two linear models. For all stages, graphs obtained by plotting the developmental rates against temperature could be described by the modification two of the Logan's model. Overall, developmental times for immature stages and egg-adult periods were similar on both Agripa and Marathon cultivars. The most favorable temperature range for nymphal development seemed to be 28-29 (second and third instars) and 31-33°C (fourth instar). Mean generation times (egg-adult) ranged from 19 d (‘Marathon’ and ‘Agripa’) at 28°C to 47 (‘Marathon’) and 46 d (‘Agripa’) at 16°C.

For the last ≈10 yr, the Gypsy Moth Life Stage (GLS) model has been used by pest managers to predict when important events in the gypsy moth, Lymantria dispar L., life cycle will occur (e.g., peak second larval instar population and male moth flight). Although the GLS model has been shown to outperform other gypsy moth phenology models, its predictions have not always been as accurate as desired. Differences between predicted and observed egg hatch phenology prompted a re-examination of the original experimental data that were used in the construction of the egg hatch submodels of the original GLS model, and a data processing error was discovered to have truncated the postdiapause experimental data. Analysis of the complete data set confirmed that developmental rates in the postdiapause phase were age and temperature dependent but that the developmental response to temperature is distinctly nonlinear at postdiapause initiation, in contrast to the indeterminate response previously reported. By incorporating the new estimates of developmental rate patterns and parameters into the GLS model, errors in the GLS-simulated egg hatch period were reduced by 33–71% and error in date of 50% cumulative egg hatch by 25–100%.

Effects of elevated CO₂ (twice ambient) on the interspecific competition among three species of wheat aphids (Sitobion avenae, Rhopalosiphum padi, and Schizaphis graminum) and on wheat-aphid interactions were studied. Wheat plants had higher biomass and yield and lower water and nitrogen content of grain when grown under elevated CO₂ than under ambient CO₂; levels of condensed tannins, total phenols, and total nonstructural carbohydrates were also higher in wheat ears under elevated CO₂. Compared with ambient CO₂, elevated CO₂ increased the abundance of R. padi when introduced solely but reduced its abundance when S. avenae was also present. The spatial distribution of wheat aphids was apparently influenced by CO₂ levels, with significantly more S. avenae on ears and a more even distribution of R. padi on wheat plants under elevated CO₂ versus ambient CO₂. Elevated CO₂ did not affect the abundance and spatial distribution of S. graminus when inoculated solely. Moreover, when S. avenae was present with either R. padi or S. graminum, spatial niche overlap was significantly decreased with elevated CO₂. When three species co-occurred, elevated CO₂ reduced spatial niche overlap between S. avenae and S. graminum and between R. padi and S. graminum. Our results suggest that increases in atmospheric CO₂ would alleviate interspecific competition for these cases, which would accentuate the abundance of and the damage caused by these wheat aphids.

A year-long field experiment showed that Reticulitermes flavipes attacked and used single stakes and wooden stake bundles differently in two habitats that varied in alternative forage. In both habitats, the number of termites present in single stakes and stake-bundles increased with stake resource size, and the number of larvae recorded from feeding sites was a close reflection of the number of workers attracted to a given food source. Over 12 mo, more single stakes and stake bundles were heavily attacked and abandoned in the pine woods compared with grassy clearings. Paradoxically, the number of termites present in single stakes and stake bundles was greater in the food-poor habitat (grassy clearings), yet the wood was less consumed compared with the food-rich habitat (pine woods). Use of stake bundles as nests and the slower rate of wood consumption in grassy clearings indicated that termites seemed to value food resources in relative terms, i.e., those termites with abundant alternative food resources consumed quickly and departed, whereas those lacking extra resources ate slowly and settled in. These field results confirm earlier laboratory results that showed that termites modified wood consumption rates dependent on the amount of food available to the colony as a whole. The appearance of mature (physogastric) reproductives (»1 yr old) in stake bundles in both habitats further indicated that termites track resources and opportunistically shift colony activities and possibly territory boundaries depending on the nature of the resources and other environmental factors. Implications for managing termites with a baiting strategy are discussed.

We studied the impact of forest edges on the fruit-feeding butterfly communities of three forest remnants in Ghana, West Africa. Community diversity was assessed using traps baited with fermenting banana. Two 200-m, edge-to-interior transects of five traps each were established in each forest. Sampling spanned 1 yr for a total of 180–210 trap days per site and resulted in 2,634 specimens and 56 species. We found significant support for an effect of forest edge on butterfly diversity. The impact of distance from edge on point estimates of diversity, i.e., total trap captures, weighted species richness, and Simpson's diversity, was unique to each forest. Multivariate analyses, which integrated species composition along with relative abundance and richness, uncovered two broad community types, interior communities (those 100, 150, and 200 m distant from the edge) and exterior communities (edge communities and those 50 m distant), indicating that edge habitat generally extends at least 50 m into the forest. However, effects of edges on community diversity were still detected as far as 100 m into the forest. Three species relatively tolerant of forest degradation emerged as indicators of edge habitat. No species were indicative of core habitat.

The hemlock woolly adelgid, Adelges tsugae Annand, is an invasive species reducing the populations of eastern hemlock, Tsuga canadensis L. Carrière, throughout the eastern United States. Systemic imidacloprid and horticultural oil are the primary chemicals used to control infestations of this invasive pest; however, the impact of these two chemicals on nontarget canopy insects is unknown. This study was initiated in November 2005 to assess the effects of (1) imidacloprid soil drench, (2) imidacloprid soil injection, (3) imidacloprid tree injections, and (4) horticultural oil applications on multiple levels of organization (composition, overall specimen abundance and species richness, guild specimen abundance and species richness, and individual species) within the phytophagous and transient canopy insect community. Community composition differed significantly among treatments based on analysis of similarity. Mean species richness and specimen abundance were significantly reduced by one or more treatments. Soil drench applications significantly reduced species richness for the detritivore and phytophaga guilds. Furthermore, specimen abundance for species in the detritivore, fungivore, phytophaga, scavenger, and transient phytophaga guilds was significantly lower in the soil drench treatment. This trend was consistent in all insect guilds examined, with the exception of the hematophaga guild that was not significantly lower than for species on the control trees. Of the 293 species documented to be associated with eastern hemlocks, 33 species were found to be directly effected by one or more of the chemical treatments.

Symbiosis is receiving increased attention among all aspects of biology because of the unifying themes it helps construct across ecological, evolutionary, developmental, semiochemical, and pest management theory. Insects show a vast array of symbiotic relationships with a wide diversity of microorganisms. These relationships may confer a variety of benefits to the host (macrosymbiont), such as direct or indirect nutrition, ability to counter the defenses of plant or animal hosts, protection from natural enemies, improved development and reproduction, and communication. Benefits to the microsymbiont (including a broad range of fungi, bacteria, mites, nematodes, etc.) often iansport, pfrom antagonists, and protection from environmental extremes. Symbiotic relationships may be mutualistic, commensal, competitive, or parasitic. In many cases, individual relationships may include both beneficial and detrimental effects to each partner during various phases of their life histories or as environmental conditions change. The outcomes of insect-microbial interactions are often strongly mediated by other symbionts and by features of the external and internal environment. These outcomes can also have important effects on human well being and environmental quality, by affecting agriculture, human health, natural resources, and the impacts of invasive species. We argue that, for many systems, our understanding of symbiotic relationships will advance most rapidly where context dependency and multipartite membership are integrated into existing conceptual frameworks. Furthermore, the contribution of entomological studies to overall symbiosis theory will be greatest where preoccupation with strict definitions and artificial boundaries is minimized, and integration of emerging molecular and quantitative techniques is maximized. We highlight symbiotic relations involving bark beetles to illustrate examples of the above trends.

Fungus-growing ants (Attini: Formicidae) engage in an obligate mutualism with fungi they cultivate for food. Although biologists have been fascinated with fungus-growing ants since the resurgence of natural history in the modern era, the early stages of research focused mainly on the foraging behavior of the leaf-cutters (the most derived attine lineage). Indeed, the discovery that the ants actually use leaf fragments to manure a fungus did not come until the 1800s. More recently, three additional microbial symbionts have been described, including specialized microfungal parasites of the ant's fungus garden, antibiotic-producing actinobacteria that help protect the fungus garden from the parasite, and a black yeast that parasitizes the ant-actinobacteria mutualism. The fungus-growing ant symbiosis serves as a particularly useful model system for studying insect-microbe symbioses, because, to date, it contains four well-characterized microbial symbionts, including mutualists and parasites that encompass micro-fungi, macro-fungi, yeasts, and bacteria. Here, we discuss approaches for studying insect-microbe symbioses, using the attine ant-microbial symbiosis as our framework. We draw attention to particular challenges in the field of symbiosis, including the establishment of symbiotic associations and symbiont function. Finally, we discuss future directions in insect-microbe research, with particular focus on applying recent advances in DNA sequencing technologies.

Mycorrhizal fungi and insects are important components of most ecosystems that are likely to interact with one another indirectly through a common host plant. In this paper, we review the literature examining the effects of insects on mycorrhizal fungi and the effects of mycorrhizal fungi on insects and show that both groups of organisms can indirectly and, occasionally directly, influence each other. We explore the mechanisms for these interactions and test a recently proposed model predicting mycorrhizal fungal community responses to herbivory. We emphasize the results of several recent studies that showed that experiments conducted in isolation are unlikely to predict the outcome of interactions between insects, plants, and mycorrhizal fungi, and we highlight the need for a community approach to the study of mycorrhizal fungal-plant-insect interactions.

Nezara viridula L. is a highly polyphagous and cosmopolitan pentatomid stink bug. Despite its economic importance, aspects of its biology are poorly understood. N. viridula has one primary bacterium associated with its gastric caeca, which females provide to offspring by smearing it on the surface of eggs during oviposition. We studied the impact of three temperatures and egg mass surface sterilization on N. viridula's nymphal development rate and reproductive performance. Our results show that maintenance of the symbiont is affected both by temperature and egg mass surface sterilization. We detected the symbiont in 100, 84, and 8.3% of the untreated control insects at 20, 25, and 30°C, respectively, by using polymerase chain reaction. In insects originated from surface sterilized egg masses, the symbiont was never detected at 20 or 30°C and was detected in only 1 of 21 insects at 25°C. Nymphal mean development time decreased with increasing temperature, but there were no differences between the sterilized and control treatments. Sterilized insects at 20°C lived longer than insects in any other treatment but never laid eggs. Life table analysis of N. viridula adults showed that net reproductive rate, intrinsic rate of increase, finite rate of increase, and gross reproductive rate were not significantly different among treatments except at 20°C for the surface sterilized treatment. Mean generation time, however, was significantly longer at 20°C (70.96 ± 4.43 d), regardless of the surface sterilization treatment. Our results highlight the effect that temperature has on the maintenance of this symbiosis and its relationship with N. viridula host's development and reproduction.

Aphids, which feed solely on plant phloem sap, have developed symbiotic associations with bacteria that provide them with the amino acids that are lacking in phloem. Three soybean aphid (Aphis glycines Mat samura) populations were screened for the presence of Buchnera aphidicola and three common species of secondary aphid symbionts (Serratia symbiotica, Hamiltonella defensa, and Regiella insecticola). Diagnostic polymerase chain reaction and subsequent DNA sequencing showed the presence of two species of symbiotic bacteria present in all three soybean aphid populations tested: B. aphidicola and Arsenophonus sp. Although Buchnera is commonly found in aphids, Arsenophonus is most commonly found in whiteflies (Hemiptera: Aleyrodidae), making the soybean aphid unique among aphids that have been tested for the presence of Arsenophonus.

The attraction of washed, medium-free cells of Pantoea (Enterobacter) agglomerans to wild, adult Rhagohtis mendax Curran, the blueberry maggot fly, was evaluated in managed blueberry fields in Maine. Attraction was evaluated using Pherocon AM and Ladd traps, each tested with or without washed bacterial cells. Field studies showed significant increases in fly captures on the Pherocon AM traps. Apple volatiles odors on Ladd traps seemed to cancel the effects of bacterial odors. Aerobic heterotrophic bacteria were isolated and identified from alimentary organs within wild R. mendax. Isolates indentified included P. agglomerans. Blueberries collected in the field were surveyed for the presence of P. agglomerans and blueberries containing blueberry maggot larvae and noninfested blueberries were analyzed for amino acid content. Maggot-infested blueberry contained twice the amino acid nitrogen than that of noninfested blueberry. P. agglomerans, like with other pest tephritids, seems to be a cosmopolite with blueberry maggot.

In this study, we assessed the interaction occurring between the rice weevil and two storage molds (Aspergillus candidus Link and Aspergillus niger Van Tiegem) that prefer different moisture regimens under rice storage conditions. Rice weevil induced rapid population growth in both of the storage molds. The colony forming units (CFUs) of A. candidus and A. niger peaked at 10^9.00 ± 0.02 and 10^7.72 ± 0.03/g, respectively. All of the rice grains were infested with the molds and eventually deteriorated; in the jars infested with A. candidus, no living weevils were found after 135 d. Suppression of the rice weevil by its larval parasitoid, Anisopteromalus calandrae (Howard), significantly retarded the growth of A. candidus but completely halted the growth of A. niger, which was replaced by xerophyllic molds including Aspergillus penicilloides Spegazzini and Wallemia sebi (Fries). Regression analyses showed that the total number of weevils was a significant factor explaining grain moisture content, which was in turn a significant factor in the growth of both mold species. The growth of A. niger was dependent on the grain moisture content (r² = 0.52), thereby suggesting that the growth of A. niger was caused primarily by activity of the rice weevil and the resulting increased grain moisture content. However, 27% of the growth of A. candidus was explained by grain moisture contents, suggesting that a factor other than the grain moisture content may also affect its growth. Suppression of rice weevil by A. calandrae could induce an A. candidus- dominant molds community, which would be a factor for consideration in biological control program.

Studies were conducted to examine the effect of treating Zinnia elegans Jacq. with soluble silicon on the performance of the green peach aphid, Myzus persicae (Sulzer). Z. elegans plants were irrigated every 2 d throughout the duration of the experiment with a nutrient solution amended with potassium silicate (K₂SiO₂), or a nutrient solution without K₂SiO₂. Length of the prereproductive period and survivorship of M. persicae were not affected by K₂SiO₂ treatment, but total cumulative fecundity and the intrinsic rate of increase (r_m) were slightly reduced on Z. elegans plants receiving soluble silicon. Quantification of silicon contentin leaf tissues using inductively coupled plasmaoptical emission spectroscopy (ICP-OES) confirmed significantly higher silicon concentrations in plants treated with K₂SiO₂ compared with control plants. High performance liquid chromatography-mass spectrometry (HPLC-MS) analysis was used to identify and quantify phenolic acids and flavonols in leaf tissue of z. elegans. Compared with untreated control plants, significant elevations in 5-caf-feoylquinic acid, p-coumaroylquinic acid, and rutin were detected in leaves of Z. elegans plants treated with K₂SiO₂, but none of seven other phenolics were significantly affected. Similarly, a slight elevation in guaiacol peroxidase activity was detected in plants treated with K₂SiO₂ Overall, these results indicate treatment of Z. elegans with soluble silicon provides a modest increase in resistance levels to M. persicae, which may be caused in part by defense-related compounds.

The twospotted spider mite, Tetranychus urticae Koch, is among the most economically important pests in strawberries (Fragaria spp.). As T. urticae feeds, it ingests mesophyll cells that contain pigments essential for physiologic function and alters radiant energy use of the leaf tissue, severely compromising plant health and productivity. In our study, diffuse reflectance spectroscopy in the visible and near infrared (VNIR) portions of the spectrum was used to identify specific spectral regions altered by T. urticae feeding and to quantitatively assess T. urticae density. During the 2006–2007 growing season, 80 strawberry leaflets with varying levels of T. urticae infestation were collected. Spectral classification of both mite density (continuous) and mite density class (categorical) were developed. Spider mite density classes were low infestation (0–20 mites/leaflet), moderate infestation (20–50 mites/leaflet), and high infestation (≥50 mites/leaflet). Continuous spectral prediction for leaf infestation was developed using partial least squares (PLS) regression. Classification trees were used to train spectra to categorical levels of infestation. Both models were calibrated with 67% of the samples, and accuracy was evaluated using the remaining 33%. Categorical validation accuracy was 81%, with odds ratios for correctly predicting extreme categories (low and high) of 33 and 47.7, respectively. Continuous validation efficiency was also high, with an r² between predicted and observed of 0.85 and a root-mean-squared error (RMSE) of 12.2 mites per leaf. Developing a spectral pest monitoring system would provide a diagnostic tool allowing early and effective intervention for precision management of T. urticae in strawberry.

Ophiostomatoid fungi are well known as economically important pathogens and agents of timber degradation. A unique assemblage of these arthropod-associated organisms including species of Gondwanamyces G. J. Marais and M. J. Wingf., and Ophiostoma Syd. and P. Syd. occur in the floral heads (infructescences) of Protea L. species in South Africa. It has recently been discovered that Ophiostoma found in Protea flower-heads are vectored by mites (Acarina) including species of: Tarsonemus Canestrini and Fonzago, Proctolaelaps Berlese, and Trichouropoda Berlese. It is, however, not known how the mites carry the fungi between host plants. In this study, we consider two possible modes of mite dispersal. These include self-dispersal between infructescences and dispersal through insect vectors. Results showed that, as infructescences desiccate, mites self-disperse to fresh moist infructescences. Long-range dispersal is achieved through a phoretic association with three beetle species: Genuchus hottentottus (F.), Trichostetha fascicularis L., and T. capensis L. The long-range, hyperphoretic dispersal of O. splendens G. J. Marais and M. J. Wingf. and O. phasma Roets et al. seemed effective, because their hosts were colonized during the first flowering season 3–4 yr after fire.

Discussions of intraguild predation (IGP) have assumed that the nutritional quality of intraguild (IG) prey is similar to that of any other prey available to the IG predator. It has been suggested therefore that generalist predators do not distinguish between healthy and parasitized aphids and thus function as facultative predators of parasitoids. More recent studies have shown that predators may selectively ingest prey of various nutritional qualities and that predators may have higher body nitrogen composition than herbivores. If so, predators may preferentially feed on other predators (i.e., IG prey) to increase their nitrogen intake. We used a system composed of larvae of the coccinellid Coccinella undecimpunctata (IG predator), the parasitoid Aphidius cohmani (IG prey), and their shared food source, the green peach aphid Myzus persicae, to test whether (1) the predator preferentially feeds on parasitized over healthy prey, (2) predatory behavior on parasitized aphids changes with time elapsed after parasitism, and (3) parasitized and healthy aphids differ in their suitability for predator development. Results indicate that, given a choice, C. undecimpunctata larvae show no preference for either parasitized or healthy prey items, regardless of parasitoid age. Feeding time, however, increased with parasitoid age, leading to a reduction in the number of prey consumed per unit time. Mummified prey were protected from predation by C. undecimpunctata larvae but the larvae were able to feed and complete development on mummies with a broken cuticle. These predators, however, had an extended developmental time and lower pupal and adult weights in comparison to larvae fed healthy aphids. That parasitized aphids are inferior prey for C. undecimpunctata larvae should act to reduce intensity of IGP in the field and the negative impact IGP has on herbivore suppression.

Lesquerella fendleri is a new crop being cultivated in the arid Southwest for the hydroxy fatty acids found in its seed oils; however, little is know about the agricultural pests that will affect the seed production of this crop or the role the crop may have as a possible source or sink for current agricultural pests in the Arizona landscape. In the early spring, Lygus bugs, some of our most important agricultural pests, are normally found in relatively small numbers on weeds; however, as lesquerella production increases, it may serve as an important early-season host for Lygus. Here we present results from olfactometer bioassays that showed a significant attraction by Lygus hesperus females to volatiles associated with flowering lesquerella. Headspace volatiles of flowering lesquerella were collected and identified by gas chromatography-mass spectrometry, and phenylacetaldehyde (PAA) was found to be the major component, followed by benzaldehyde and Z-3- hexenyl acetate. In the field, we examined the Lygus spp. complex, as well as the prevalence of other herbivores and select predators, and monitored their responses to unbaited sticky traps of various colors and PAA-baited green and blue sticky traps. Green, blue, and clear sticky traps captured significantly more Lygus spp. (L. elisus in particular) than opaque yellow and red traps, but PAA-baited blue and green traps did not capture more Lygus than unbaited traps. Collops spp., however, were collected in higher numbers on PAA-baited traps, suggesting that this compound might provide a means of recruiting and/or retaining this particular natural enemy.

The ability of three cyanoacrylate glues to ensure a durable bond between the Colorado potato beetle, Leptinotarsa decemlineata (Say), the plum curculio, Conotrachelus nenuphar (Herbst), or the corn rootworms (Western Corn Rootworm, Diabrotica virgifera virgifera LeConte and Northern Corn Rootworm, Diabrotica longicornis Smith and Lawrence) and the harmonic radar tag without impact on behavior and survival was assessed as part of a study on the use of harmonic radar technology to track these insect pests. Droplets of 0.1 mg of Krazy Glue, Loctite, and Bowman FSA applied to the pronotum had no effect on the survival of the Colorado potato beetle or plum curculio after 5 and 7 d, but caused >40% mortality after only 4 h with both the western and northern corn rootworms. The three glues created an effective bond lasting 4–5 d between the harmonic radar tag and the Colorado potato beetle in >85% of cases and the plum curculio in almost 50% of cases. There was no detectable impact of the glue treatment on feeding or walking behavior of the Colorado potato beetle. Analysis of the same behaviors with the plum curculio showed no impact on the ability to walk on a vertical surface, the speed of travel, or the duration of travel. There was no significant impact on feeding by female plum curculio but indication that males treated with Krazy Glue fed less. Overall, results quantified the effectiveness of the cyanoacrylate glues at providing a durable bond with no significant impact on mobility or behavior of the Colorado potato beetle or plum curculios. However, the toxicity of the glues against the corn rootworms suggests that similar toxicity or sublethal effects may exist with other insects.

Understanding of the mating and dispersal behavior of the western corn rootworm, Diabrotica virgifera virgifera (LeConte), is essential to predicting potential resistance to Bt corn technologies recently deployed to combat this pest. To quantify movement of male beetles, field studies were conducted during 2006 and 2007 in commercial Bt cornfields that included the Environmental Protection Agency-mandated 20% refuge acreage. Wing traps containing a single virgin female beetle were placed along transects throughout these fields. Male beetles were collected from the sticky bottoms of traps to compare the mean number of beetles captured at the different transect distances. Gut contents of each captured male were assayed with protein test strips to determine if the Bt protein (Cry3Bb1) was present. This provided an estimate of the distances traveled by males to reach virgin females. These data indicated that the mean number of males captured ≈200 m from refuge corn was not significantly different than the mean number of males captured close to the refuge (<22 m). Complementary field observations were conducted to determine how far newly emerged female beetles moved before mating and the time of day mating occurs. Results indicated that females do not move far from the site of emergence before mating and do not mate within the first 4 h of adult life. The implications of these data for movement and mating patterns of adult rootworms in Bt/refuge environments are discussed.

Homalodisca vitripennis (Germar) and related species have caused millions of dollars in damage to southern California vineyards in recent years through the vectoring of Pierce's disease. However, the effects of surrounding vegetation on the dispersal and distribution of H. vitripennis are poorly understood. Therefore, the relationship between dispersal rates and patch quality was tested, as well as the basic predictions of the marginal value theorem. Additional experiments were conducted to compare the H. vitripennis distribution in an isolated crape myrtle (Lagerstroemia indica) patch and a L. indica patch bordering two alternative host patches. In mark-release-recapture tests, H. vitripennis dispersed farther from the release point in a patch of low-quality host plants (Prunus persica) than in patches of high-quality host plants (L. indica). In addition, H. vitripennis remained in L. indica patches longer than in P. persica patches and adjusted patch residence times in P. persica in correlation with known changes in plant physiology. These data suggest that H. vitripennis follows the basic predictions of marginal value theorem. In distribution tests, H. vitripennis were more abundant in the patch center than patch edges in the isolated L. indica patch, but in a patch bordering cottonwood (Populus sp.) and peach (P. persica), H. vitripennis numbers were generally higher along the edges of the patch. These data suggest that alternate hosts bordering cropping systems may be important to the spatial dynamics of H. vitripennis. Implications of these spatial observations on the biology of H. vitripennis and potential control methods are discussed.

Numerous studies of insect species have shown that a subset of female cuticular hydrocarbons is used as short-range or contact pheromones. Here, we studied the possible use of contact pheromones in the mating behavior of the weevil Aegorhinus superciliosus, a native species of Chile. Males mounted females only after antennal contact with the female's cuticle, and only 33% of the males attempted to mate with dead females washed with solvent. When a glass rod (dummy) was coated with female cuticular extracts, males exhibited behaviors similar to those observed with females. A preliminary gas chromatography-mass spectrometry (GC-MS) analysis of cuticular extracts indicated that males and females share a series of aliphatic hydrocarbons but that the relative abundance of some of these compounds differ between the sexes. These results suggest that cuticular lipids mediate mating behavior of the raspberry weevil and provide the first evidence of contact pheromones in curculionids.

We assessed the performance of Pseudacteon curvatus Borgmeier with respect to the social form of Solenopsis invicta Buren in Argentina. In the field, we studied the effect the parasitoid on size and proportion of ant foragers. In the laboratory, we evaluated P. curvatus oviposition preferences; host size elected; developmental periods; and sexual size dimorphism, sex ratio, and parasitoid survivorship. P. curvatus affected the average size of foraging workers on both social forms diminishing the proportion of big and increasing the proportion of minor workers. P. curvatus required a shorter orientation time and exhibited a greater number of attacks when ovipositing on monogynes workers. In the laboratory, host sizes elected by P. curvatus were similar between social forms. However, attacks on polygyne colonies were more variable, increasing the number of unviable offspring. Developmental times of females and males of P. curvatus were similar for both social forms, but total developmental periods were shorter for males from monogyne colonies. We did not find differences between sexes in emerging adults' size by social form and the female: male sex ratio was 1:1 for both social forms. P. curvatus pupae survival and adult emergence per trial from monogyne colonies were greater than from polygyne colonies. The rarity of polygyne S. invicta in its native range may prevent this phorid from adjusting its life history to that social form. Consequences of applying this phorid in biological control are discussed.

Perimeter trap cropping (PTC) is a method of integrated pest management (IPM) in which the main crop is surrounded with a perimeter trap crop that is more attractive to pests. Blue Hubbard (Cucurbita maxima Duch.) is a highly effective trap crop for butternut squash (C. moschata Duch. ex Poir) attacked by striped cucumber beetles (Acalymma vittatum Fabricius), but its limited marketability may reduce adoption of PTC by growers. Research comparing border crop varieties is necessary to provide options for growers. Furthermore, pollinators are critical for cucurbit yield, and the effect of PTC on pollination to main crops is unknown. We examined the effect of five border treatments on herbivory, pollination, and yield in butternut squash and manipulated herbivory and pollination to compare their importance for main crop yield. Blue Hubbard, buttercup squash (C. maxima Duch.), and zucchini (C. pepo L.) were equally attractive to cucumber beetles. Border treatments did not affect butternut leaf damage, but butternut flowers had the fewest beetles when surrounded by Blue Hubbard or buttercup squash. Yield was highest in the Blue Hubbard and buttercup treatments, but this effect was not statistically significant. Native bees accounted for 87% of pollinator visits, and pollination did not limit yield. There was no evidence that border crops competed with the main crop for pollinators. Our results suggest that both buttercup squash and zucchini may be viable alternatives to Blue Hubbard as borders for the main crop of butternut squash. Thus, growers may have multiple border options that reduce pesticide use, effectively manage pests, and do not disturb mutualist interactions with pollinators.

The location of wild and cultivated host plants by pepper weevil (Anthonomus eugenii Cano) may be aided by visual cues, the male-produced aggregation pheromone, herbivore-induced, or constitutive host plant volatiles. The attractiveness of constitutive plant volatiles to pioneer weevils is important in understanding, and perhaps controlling, dispersal of this insect between wild and cultivated hosts. Ten-day-old male and 2- and 10-day-old female weevils were tested in short-range Y-tube assays. Ten-day-old male and female weevils were attracted to the volatiles released by whole plants of three known oviposition hosts, ‘Jalapeno’ pepper, American black nightshade, and eggplant, as well as tomato, a congener, which supports feeding but not oviposition. Two-day-old females were attracted to all plants tested, including lima bean, an unrelated, nonhost plant. Fruit volatiles from all three hosts and flower volatiles from nightshade and eggplant were also attractive. In choice tests, weevils showed different preferences for the oviposition hosts, depending on age and sex. Upwind response of 10-day-old male and female weevils to host plant volatiles was also tested in long-range wind tunnel assays. Weevils responded to pepper, nightshade, and eggplant volatiles by moving upwind. There was no difference in the observed upwind response of the weevils to the three host plants under no-choice conditions. Reproductively mature pepper weevils can detect, orient to, and discriminate between the volatile plumes of host plants in the absence of visual cues, conspecific feeding damage, or the presence of their aggregation pheromone.

Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is an important worldwide pest of citrus that vectors bacteria (Candidatus Liberibacter spp.) responsible for huanglongbing (citrus greening disease). We examined the behavioral responses of mated and unmated D. citri of both sexes to odors from host plants in a Y-tube olfactometer, with and without visual cues. The host plants tested were ‘Duncan’ grapefruit (Citrus paradisi Macfayden), sour orange (Citrus aurantium L.), navel orange (C. sinensis L.), and Murraya paniculata L. Jack. Responses varied by plant species, psyllid sex and mating status, and the presence of a visual cue. Evidence of attraction generally was stronger in females and in mated individuals of both sexes relative to virgins. The presence of a visual cue typically enhanced attractiveness of olfactory cues; in no case did unmated individuals show evidence of attraction to host plant odors in the absence of a visual cue. In the absence of visual cues, mated females and males showed evidence of attraction only to odors from sour orange and navel orange, respectively. Psyllids exhibited anemotactic responses when assayed with plant odors alone but showed strong evidence of attraction only when olfactory and visual cues were combined, suggesting that olfactory cues facilitate orientation to host plants but may be insufficient alone. Antennal responses to citrus volatiles were confirmed by electroantennogram. The results reported here provide evidence that D. citri uses olfactory and visual cues in orientation to host plants and suggest the possibility of using plant volatiles in monitoring and management of this pest.

The exotic beetle Ophraella communa LeSage was first found in 1996 in Japan and has rapidly expanded its distribution. This study examined the effect of several factors on the flight activity of this beetle and estimated its dispersal potential by measuring its flight time on a flight mill system. The beetles exhibited low flight activity at the age of 1–3 d posteclosion; however, after 4 d, it increased and thereafter remained high. The beetles reduced flight activity under the dark photophase, although they flew during both light and dark phases. Flight activity was lower in adults reared from hatching under a 12:12 (L:D)-h photoperiod than in those reared under a 16:8-h photoperiod; the shorter photoperiod was found to induce reproductive diapause. This photoperiodic response could explain seasonal changes in flight activities in which fourth-generation adults displayed the lowest activity before overwintering. The female beetles flew, at maximum, for 385 min during a 23-h experimental period. Based on this value, the flight distance was estimated to be 25 km/23 h, suggesting a high dispersal potential of this beetle.

Prolonged exposure to low temperature generally induces deleterious effects on survival and reproduction of insects. Reproduction costs are well documented in cold-exposed female parasitoids, but there is little information concerning males. In some species, low temperature is suspected to cause male sterility. Mummies of the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiinae) were exposed to either ?uctuating thermal regimens (FTR: 4°C, 22 h; 20°C, 2 h) or constant low temperature (CLT: 4°C) for 15 d. We verified whether cold exposure can sterilize males and evaluated treatment-related survival, reproductive potential, and mobility parameters. Sterility trials showed that cold-exposed males were all fertile. Survival and reproductive potential of males (e.g., mating success, premating period, and competition for mating) were negatively affected when individuals were exposed to CLT. These alterations were associated with a reduction in locomotion performances during premating period. When parasitoids were exposed to FTR, survival, reproductive potential, and mobility parameters were unaffected. The reduced survival and mobility under CLT, probably results physiological perturbations: processes that may have a limited impact on individuals exposed to FTR. The consequence of mobility reduction on partner acceptance and competitive mating ability is discussed.

Diamesa mendotae Muttkowski is commonly observed emerging during winter at low air temperatures from Minnesota streams, but little is known about the winter dynamics of this and other winter-emerging aquatic insects. Biweekly collections of surface-floating pupal exuviae indicated that this species emerged from October through May, when water temperatures were less than ≈10C. Emergence occurred continuously through winter, with a lull during January and February. Development of larvae from in situ growth enclosures supported emergence data and indicated that the reduction and halt of emergence in the spring was related to increasing water temperatures (>10°C), which were unsuitable for the growth or survival of the larvae. Development continued through January when water temperatures were at their lowest for the study stream and therefore did not explain the mid-winter lull in emergence. Growth rates of D. mendotae were not greater than other chironomid taxa at similar temperatures, indicating that lower critical thermal limits for growth allow this species to dominate ground-water influenced streams during the winter in Minnesota. The results of this study show that D. mendotae is well suited for growth and development at low temperatures and provides an assessment of important factors that regulate this species at low water and air temperatures.

The rice stem borer, Chilo suppressalis Walker, which is a key rice pest in northern parts of Iran, overwinters in rice stubble and weeds as mature larvae. Diapause of this pest is initiated between October to November and terminates in March. Seasonal variations in the supercooling point, survival at low temperatures, and sugar contents were studied in field-collected larvae during different phases of diapause. Ambient temperature was lowest in January and February when larvae were at the highest diapause intensity and achieved a high degree of cold hardiness at -10, -15, and -20°C. Glycerol, a major cryoprotectant, reached a peak in January. It appeared that cold hardiness in the larvae is closely associated with the diapause. For the first time, this study suggests that glucose and glycogen are converted to glycerol during cold seasons, but trehalose has no definite role in the interconversion. During the coldest months, supercooling points (SCPs) increased (around — 11°C), and larvae could survive below their SCP values, showing that overwintering larvae of C. suppressalis are freeze tolerant in Iran. Our findings suggest that cold hardiness and diapause are essential components for this species. The ovewintering larvae have high capacity of cold hardiness and can overcome severe winters. Understanding of cold hardiness and overwintering behavior of this species may help in integrated pest management of the rice stem borer in paddy fields.

The exotic beetle Ophraella communa LeSage (Coleoptera: Chrysomelidae) was first found in 1996 in Japan and has rapidly expanded its distribution. This study investigated variation in flight activity and its genetic basis in this beetle by measuring its flight time on a flight mill system. The O. communa population exhibited substantial variation in flight activity among individuals. More than 30% of the beetles did not fly at all during a 23-h experimental period, whereas 20–26% of the beetles flew for over 60 min. Bidirectional artificial selection based on total flight time (0 or >60 min) significantly shifted the distributions of flight time and percentage of beetles flying after several generations. Repeatability of the following five flight components was analyzed: the total flight time, longest duration of single flight, mean duration of single flights, number of single flights, and a fly-or-not criterion (flying at least once [1] or nothing at all [0]) because it defines a theoretical upper limit of heritability. Among them, the fly-or-not criterion had the highest repeatability (0.797), followed by the total flight time (0.648). The fly-or-not criterion assumes a threshold trait, whereas the total flight time is regarded as a continuous trait. The realized heritabilities of these traits were estimated at 0.206–0.864 based on the threshold trait and 0.125–0.531 based on the continuous trait.

The western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a pest of both corn and dry bean crops. At the beginning of the 21st century, the species began to extend its range out of the Great Plains, eastward through the Corn Belt. This rapid range expansion is remarkable because the species distribution had been stable for at least the previous half century, despite the apparent abundance of suitable habitat (i.e., cornfields) immediately to the east. We hypothesized that if the western bean cutworm had to overcome a stable barrier to movement before starting the current range expansion, it probably experienced a genetic bottleneck in doing so. To test this hypothesis, variation in the mitochondrial NADH dehydrogenase one (ND1) gene was studied in populations from Wyoming, Nebraska, and Iowa. No differences in overall genetic diversity or haplotype frequencies indicative of a bottleneck were observed between the recently founded populations in Iowa and the established populations in Wyoming and Nebraska. This result suggests that the sudden loss of an ecological exclusion mechanism, allowing the species to move east in appreciable numbers, is more likely to have triggered the range expansion than the surmounting of an extrinsic barrier to movement. The nature of this mechanism is unknown but might be related to recent changes in corn farming practices and technology.

Field studies were conducted over a 3-yr period to investigate the potential effects of cultivating transgenic maize hybrids containing a Cry1F insect-resistant protein on nontarget arthropod abundance. The narrow spectrum of activity of Cry1F against a subset of lepidopteran pest species would not suggest broad-spectrum effects on nontarget arthropods. However, because of the insecticidal nature of Bt proteins, an alternate hypothesis is that some nontargets may be affected by exposure to the protein. To examine this hypothesis at the field level, monitoring for nontarget organism abundance was initiated at four locations across the U.S. Corn Belt from 2004 through 2006. At each location, paired fields (≈0.8 ha each) of commercial Cry1F maize hybrids and isogenic nontransgenic control hybrids were planted. Sampling methods used to monitor nontarget organisms included visual surveillance, sticky cards, pitfall traps, and litterbags. Data were analyzed using multivariate analyses to look for a general community level response to the treatments. Analysis of variance was conducted on individual taxa to detect differences distinct from the primary community response. Community level analyses of the nontarget arthropod abundance showed no significant impact on community abundance when comparing Bt with non-Bt maize fields. Analyses of the individual taxa also showed no significant differences in abundance between Bt and non-Bt fields. Results of these studies confirm earlier laboratory testing and support the hypothesis that Cry1F maize does not produce adverse effects on nontarget arthropods occurring in maize fields.