Flying on empty: reduced mitochondrial function and flight capacity in food-deprived monarch butterflies.

Mitochondrial function is fundamental to organismal performance, health and fitness - especially during energetically challenging events, such as migration. With this investigation, we evaluated mitochondrial sensitivity to ecologically relevant stressors. We focused on an iconic migrant, the North American monarch butterfly (Danaus plexippus), and examined the effects of two stressors: 7 days of food deprivation and infection by the protozoan parasite Ophryocystis elektroscirrha (known to reduce survival and flight performance). We measured whole-animal resting metabolic rate (RMR) and peak flight metabolic rate, and mitochondrial respiration of isolated mitochondria from the flight muscles. Food deprivation reduced mass-independent RMR and peak flight metabolic rate, whereas infection did not. Fed monarchs used mainly lipids in flight (respiratory quotient 0.73), but the respiratory quotient dropped in food-deprived individuals, possibly indicating switching to alternative energy sources, such as ketone bodies. Food deprivation decreased mitochondrial maximum oxygen consumption but not basal respiration, resulting in lower respiratory control ratio (RCR). Furthermore, food deprivation decreased mitochondrial complex III activity, but increased complex IV activity. Infection did not result in any changes in these mitochondrial variables. Mitochondrial maximum respiration rate correlated positively with mass-independent RMR and flight metabolic rate, suggesting a link between mitochondria and whole-animal performance. In conclusion, low food availability negatively affects mitochondrial function and flight performance, with potential implications for migration, fitness and population dynamics. Although previous studies have reported poor flight performance in infected monarchs, we found no differences in physiological performance, suggesting that reduced flight capacity may be due to structural differences or low energy stores.

Instar Determination of Blattella asahinai (Blattodea: Ectobiidae) From Digital Measurements of the Pronotum Using Gaussian Mixture Modeling and the Number of Cercal Annuli.

The Asian cockroach, Blattella asahinai Mizukubo, has expanded its range throughout the southeastern United States since its introduction into Florida. Unlike its closest relative, the German cockroach, Blattella germanica (L.), B. asahinai lives outdoors and can fly. There is little information on the biology and development of B. asahinai, including the number of instars during nymphal development. To estimate the number of instars of B. asahinai, nymphs were photographed, sexed, and the lengths and widths of their pronota were measured digitally. The number of instars of B. asahinai was estimated using Gaussian mixture models with the pronotal data. The most probable model and its clusters were selected to assign individuals to an instar. Instars were also determined by counting the number of cercal annuli of nymphs. Both clustering and cercal annuli indicated that B. asahinai most frequently had six instars when reared at 30°C. Growth did not strictly follow the Brooks-Dyar Rule, because nymphs had different numbers of instars and different growth patterns. Although Gaussian mixture models are not efficient for field sampling experiments, digital measurements may provide a way to estimate instars with live specimens in development studies without handling the animals in a way that may alter growth.

Estimating the critical thermal maximum (CTmax) of bed bugs, Cimex lectularius: Comparing thermolimit respirometry with traditional visual methods.

Evaluating the critical thermal maximum (CTmax) in insects has provided a number of challenges. Visual observations of endpoints (onset of spasms, loss of righting response, etc.) can be difficult to measure consistently, especially with smaller insects. To resolve this problem, Lighton and Turner (2004) developed a new technique: thermolimit respirometry (TLR). TLR combines real time measurements of both metabolism (V·CO2) and activity to provide two independent, objective measures of CTmax. However, several questions still remain regarding the precision of TLR and how accurate it is in relation to traditional methods. Therefore, we evaluated CTmax of bed bugs using both traditional (visual) methods and TLR at three important metabolic periods following feeding (1d, 9d, and 21d). Both methods provided similar estimates of CTmax, although traditional methods produced consistently lower values (0.7-1°C lower than TLR). Despite similar levels of precision, TLR provided a more complete profile of thermal tolerance, describing changes in metabolism and activity leading up to the CTmax, not available through traditional methods. In addition, feeding status had a significant effect on bed bug CTmax, with bed bugs starved 9d (45.19[±0.20]°C) having the greatest thermal tolerance, followed by bed bugs starved 1d (44.64[±0.28]°C), and finally bed bugs starved 21d (44.12[±0.28]°C). Accuracy of traditional visual methods in relation to TLR is highly dependent on the selected endpoint; however, when performed correctly, both methods provide precise, accurate, and reliable estimations of CTmax.

Antennal olfactory sensilla responses to insect chemical repellents in the common bed bug, Cimex lectularius.

Populations of the common bed bug Cimex lectularius (Hemiptera; Cimicidae), a temporary ectoparasite on both humans and animals, have surged in many developed countries. Similar to other haematophagous arthropods, C. lectularius relies on its olfactory system to detect semiochemicals in the environment, including both attractants and repellents. To elucidate the olfactory responses of the common bed bug to commonly used insect chemical repellents, particularly haematophagous repellents, we investigated the neuronal responses of individual olfactory sensilla in C. lectularius' antennae to 52 insect chemical repellents, both synthetic and botanic. Different types of sensilla displayed highly distinctive response profiles. While C sensilla did not respond to any of the insect chemical repellents, Dγ sensilla proved to be the most sensitive in response to terpene-derived insect chemical repellents. Different chemical repellents elicited neuronal responses with differing temporal characteristics, and the responses of the olfactory sensilla to the insect chemical repellents were dose-dependent, with an olfactory response to the terpene-derived chemical repellent, but not to the non-terpene-derived chemical repellents. Overall, this study furnishes a comprehensive map of the olfactory response of bed bugs to commonly used insect chemical repellents, providing useful information for those developing new agents (attractants or repellents) for bed bug control.

Field and laboratory efficacy of three insecticides for population management of the Asian cockroach (Dictyoptera: Blattellidae).

Toxicity, repellency, and performance of three insecticides, beta-cyfluthrin EC, fipronil granules, and an essential oil EC formulation, were evaluated against the Asian cockroach, Blattella asahinai Mizukubo, in field and laboratory experiments. The beta-cyfluthrin EC and fipronil granules were significantly more toxic than the essential oil EC formulation under continuous exposure conditions, with LT50 values of 0.014, 0.45, and 11.45 d, respectively. The beta-cyfluthrin EC and fipronil granules were also significantly more toxic than the essential oil EC formulation in an Ebeling choice box test with LT50 values of 0.64, 1.98, and 59.64 d, respectively. Field applications of insecticides at label rates to Asian cockroach populations in Dothan, AL, showed that beta-cyfluthrin EC and fipronil granules reduced populations by 100% at 7 and 30 d after treatment. The essential oil EC formulation initially reduced populations by 68% at 7 d, but control diminished to 2% by 30 d. Results of the field applications and laboratory experiments demonstrate that the beta-cyfluthrin EC and fipronil granules provide excellent control of Asian cockroach populations.

Topical and vapor toxicity of saturated fatty acids to the German cockroach (Dictyoptera: Blattellidae).

Topical and fumigant toxicity of saturated aliphatic fatty acids with chain lengths of C1 through C14 were determined against the German cockroach, Blattella germanica (L.). In the C1 to C11 series, topical toxicity (LD50 in milligram per adult male) ranged from 0.145 (C1) to 0.322 mg (C2). Toxicity declined dramatically with C12 and C14 acids whose LD50 values could not be calculated. The relative fumigation toxicity (LC50 in microliter per liter) of C1 through C5 acids was positively correlated with topical toxicity with values ranging from 6.159 (C3) to 12.302 microl/liter (C2). Fumigant toxicity decreased sharply with C6 (LC50 = 37.691 microl/liter) and there was no mortality of cockroaches exposed to vapors from C7 to C14 acids. The low fumigant toxicity of the C6 to C11 acids was correlated with their relatively low vapor pressure, but differences in diffusion of the vapors into the spiracles and subsequent passage to the target sites may have also been involved.

Toxicity of cockroach gel baits to the oothecal parasitoid Aprostocetus hagenowii (Hymenoptera: Eulophidae) and implications for cockroach integrated pest management.

Aprostocetus hagenowii (Ratzeburg) is a parasitoid wasp that parasitizes the oothecae of peridomestic pest cockroaches. A. hagenowii has been used in integrated pest management (IPM) programs for cockroach control but little is known about how this parasitoid responds to the insecticides commonly used for cockroach management. Five insecticidal gel bait products containing indoxacarb, clothianidin, fipronil, dinotefuran, or abamectin B1 were tested for their toxicity towards A. hagenowii and the American cockroach, Periplaneta americana (L.; Blattodea: Blattidae), a host of A. hagenowii and a common pest. All baits were tested as fresh and 1-d aged deposits. Indoxacarb was the only active ingredient that did not cause significant (P < 0.05) A. hagenowii mortality compared to the control in both the fresh and aged gel experiments (Median survival time [MST]s: 168 h fresh, 72 h aged). Clothianidin caused the lowest A. hagenowii MSTs across experiments (24 h, fresh and aged). All baits caused significant P. americana mortality as fresh and 1-d aged deposits (P < 0.05). Indoxacarb appears most compatible with A. hagenowii in cockroach IPM.

Common consumer residual insecticides lack efficacy against insecticide-susceptible and resistant populations of the German cockroach (Blattodea: Ectobiidae).

The German cockroach, Blattella germanica (L.) (Blattodea: Ectobiidae), is a ubiquitous pest in affordable housing. They represent a major threat to human health due to their contribution of asthma-exacerbating allergens and the potential to transfer pathogenic microorganisms indoors. Despite well-documented pyrethroid resistance, pyrethroid-based broadcast residual insecticide products are often used by residents to control cockroaches in their homes. Additionally, there is little empirical independent testing of these products. Thus, it remains unclear how effective these commonly used do-it-yourself products are at controlling German cockroaches. This study represents a comprehensive examination of the efficacy of these products with direct, limited, and continuous exposure assays on a variety of common household surfaces on field populations of cockroaches with varying levels of pyrethroid resistance. While most products performed well when applied directly to test insects, mortality was substantially lower across all surfaces with limited exposure (30 min). In continuous exposure assays on a nonporous surface, products took at least 24 hr to cause 100% mortality in a field population, with some products taking up to 5 d to achieve 100% mortality. The findings of this study demonstrate a lack of residual efficacy from common pyrethroid-based consumer-use pesticides products. Given that it is not feasible to find and treat every cockroach in a home directly, the residuality of spray-based formulations is critical for products designed to control German cockroaches. Without residual efficacy, as shown in the consumer aerosol and spray products tested, we expect these products to add little to no value to cockroach control.

Mulch preferences of the Asian cockroach (Dictyoptera: Blattellidae).

Mulch preferences of the Asian cockroach, Blattella asahinai Mizukubo, were determined in a series of laboratory experiments. Because this species is a peridomestic pest, mulch preferences may be a key part of an integrated pest management program for homeowners. Five mulches were used: cypress, oak leaf litter, pine straw, rubber, and topsoil. Large arena experiments showed that adult male Asian cockroaches preferred oak leaf litter and pine straw, while adult females preferred oak leaf litter and rubber mulches. Nymphal stages preferred rubber (48.3-62.5% for small and medium instars, respectively) to all other mulches. All stages of the Asian cockroach showed very little preference to topsoil (0%) and cypress mulch (6.3%). Ebeling choice box tests confirmed lack of preference or repellency of adult males to topsoil (17.8 +/- 3.6%) and rubber mulch (15.7 +/- 3.6%). Continuous exposure experiments indicated that pine straw was significantly more toxic to adult males than other mulches (66.7 +/- 18.4% mortality at 7 d). Mulch preferences of the Asian cockroach may be mediated by characteristics of the interstitial spaces in the different mulches. Rubber mulch afforded smaller, more humid spaces that were inaccessible to adults. Because cypress mulch was least preferred by nymphs and adults, use of cypress mulch in an integrated pest management program around homes may help to reduce Asian cockroach populations and limit insecticide exposure to humans, animals, and the environment.

Differential development and survival of Blattella asahinai and Blattella germanica (Blattodea: Ectobiidae) at six constant temperatures.

The Asian cockroach, Blattella asahinai Mizukubo, is a peridomestic nuisance pest in the southeastern United States. Blattella asahinai is the closest relative to Blattella germanica (L.), the German cockroach, one of the most prolific and widespread domestic pests. Because these two species live in different habitats, they are expected to have differential development patterns reflecting environmental adaptations. Development of B. asahinai and B. germanica cockroach nymphs were observed at six constant temperatures ranging from 10 to 35 °C. At 10 °C and 15 °C, all nymphs died in the first instar, but B. germanica nymphs survived longer (10 °C: 12.9 d; 15 °C: 42.9 d) than B. asahinai nymphs (10 °C 8.2 d; 15 °C 18.4 d) at both temperatures. At 20 °C, 25 °C, and 30 °C, B. asahinai consistently had more instars and longer stadia than B. germanica. At 35 °C, only B. germanica was able to complete nymphal development; cannibalism among B. asahinai nymphs during molting was often observed at this temperature. The results for B. asahinai corroborated previously estimated growth patterns. The lower nymphal development threshold was 14.1 °C for B. germanica and 13.7 °C for B. asahinai. Comparing the development of B. germanica directly with its closest relative reveals specific physiological adaptations that B. germanica has developed for the indoor biome.

The prevalence of Wolbachia in multiple cockroach species and its implication for urban insect management.

Cockroach management relies heavily on the use of conventional insecticides in urban settings, which no longer provide the anticipated level of control. Knowledge of cockroach endosymbionts, like Wolbachia, might provide novel avenues for control. Therefore, we screened 16 cockroach species belonging to 3 families (Ectobiidae, Blattidae, and Blaberidae) for the presence of Wolbachia. We mapped the evolution of Wolbachia-cockroach relationships based on maximum likelihood phylogeny and phylogenetic species clustering on a multi-loci sequence dataset (i.e., coxA, virD4, hcpA, and gatB) of Wolbachia genes. We confirmed the previous report of Wolbachia in 1 Ectobiid species; Supella longipalpa (Fab.), and detected the presence of Wolbachia in 2 Ectobiid species; Balta notulata (Stål) and Pseudomops septentrionalis Hebard, and 1 Blaberid species; Gromphadorhina portentosa (Schaum). All cockroach-associated Wolbachia herein detected were clustered with the ancestor of F clade Wolbachia of Cimex lectularius L. (bed bugs). Since Wolbachia provision C. lectularius with biotin vitamins that confer reproductive fitness, we screened the cockroach-associated Wolbachia for the presence of biotin genes. In toto, our results reveal 2 important findings: (i) Wolbachia is relatively uncommon among cockroach species infecting about 25% of species investigated, and (ii) cockroach-associated Wolbachia have biotin genes that likely provide nutritional benefits to their hosts. Thus, we discuss the potential of exploring Wolbachia as a tool for urban insect management.

Potential of the oothecal parasitoid Aprostocetus hagenowii (Hymenoptera: Eulophidae) as a biological control agent for the Turkestan cockroach (Blattodea: Blattidae).

The Turkestan cockroach, Blatta lateralis (Walker), is a peridomestic pest of growing concern in the US Southwest. The parasitoid Aprostocetus hagenowii (Ratzburg) is used in IPM programs targeting other blattid cockroach species and may aid in B. lateralis suppression. Information about the ability of A. hagenowii to parasitize B. lateralis is lacking. A no-choice host-switching experiment was used to test A. hagenowii acceptance of B. lateralis oothecae, and a multigenerational no-choice experiment was used to determine the suitability of B. lateralis as a host for A. hagenowii over several months of rearing. Periplaneta americana (L.) (Blattodea: Blattidae), the preferred host of A. hagenowii, and Blatta orientalis L., a known host and relative of B. lateralis, were used for comparison. Development time was similar among hosts and generations (P > 0.05). Parasitism success and proportion of female progeny declined significantly with subsequent generations on both Blatta spp. (parasitism success: χ2 = 14.916; df = 2; P = 0.001; proportion female: H = 6.364; df = 2; P = 0.041). These results suggest that A. hagenowii may initially aid in suppression of B. lateralis, but an overall decline in fitness will require repeated releases or provisioning of P. americana oothecae. Development of a strain more suitable for B. lateralis control may be possible via selection from laboratory strains or through use of wild A. hagenowii from areas where B. lateralis is present.

Subterranean termite open-air foraging and tolerance to desiccation: Comparative water relation of two sympatric Macrotermes spp. (Blattodea: Termitidae).

The foraging patterns of termites are strongly related to physiological limits in overcoming desiccation stress. In this study, we examined moisture preferences and physiological characteristics of Macrotermes carbonarius (Hagen) and M. gilvus (Hagen) as both exhibit conspicuous patterns of foraging activity. Despite both species showing no significant differences in calculated cuticular permeability, and percentage of total body water, they differed greatly in rate of water loss and surface area to volume ratio. For example, M. carbonarius which had a lower surface area to volume ratio (29.26-53.66) showed lower rate of water loss and percentage of total body water loss. This also resulted in higher LT(50) when exposed to extreme conditions (≈2% RH). However, contrasting observations were made in M. gilvus that has smaller size with higher surface area to volume ratio of 40.28-69.75. It is likely that the standard equation for calculating insect surface areas is inadequate for these termite species. The trend was further supported by the result of a moisture preference bioassay that indicated M. carbonarius had a broader range of moisture preference (between 5% and 20%) than M. gilvus which had a relatively narrow moisture preference (only 20%). These results explain why M. carbonarius can tolerate desiccation stress for a longer period foraging above-ground in the open air; while M. gilvus only forages below ground or concealed within foraging mud tubes.

Efficacy of commercial baits and new active ingredients against firebrats and silverfish (Zygentoma: Lepismatidae).

Commercial baits containing boric acid, hydramethynon, and indoxacarb were tested against the firebrat, Thermobia domestica (Packard), and silverfish, Lepisma saccharina L. (both Zygentoma: Lepismatidae), under laboratory conditions. Three boric acid baits were consumed in significantly smaller amounts than untreated control food and did not effectively control either species. Baits containing hydramethylnon and indoxacarb were consumed in greater amounts than boric acid baits, but were relatively ineffective, with LT50 values >9 d. Presence or absence of competitive untreated food did not consistently affect bait efficacy. A ground oat matrix was used to evaluate the potential effectiveness of abamectin, chlorfenapyr, dinotefuran, fipronil, hydramethylnon, metaflumizone, and novaluron baits. The most effective compound was chlorfenapyr. At 0.05 and 0.20% (wt:wt) rates, chlorfenapyr baits produced LT50 values, for both species, ranging from 2 to 4 d. All other compounds had LT50 values >7 d.

Why Do Insects Close Their Spiracles? A Meta-Analytic Evaluation of the Adaptive Hypothesis of Discontinuous Gas Exchange in Insects.

The earliest description of the discontinuous gas exchange cycle (DGC) in lepidopterous insects supported the hypothesis that the DGC serves to reduce water loss (hygric hypothesis) and facilitate gaseous exchange in hyperoxia/hypoxia (chthonic hypothesis). With technological advances, other insect orders were investigated, and both hypotheses were questioned. Thus, we conducted a meta-analysis to evaluate the merit of both hypotheses. This included 46 insect species in 24 families across nine orders. We also quantified the percent change in metabolic rates per °C change of temperature during the DGC. The DGC reduced water loss (-3.27 ± 0.88; estimate ± 95% confidence limits [95% CI]; p < 0.0001) in insects. However, the DGC does not favor gaseous exchange in hyperoxia (0.21 ± 0.25 [estimate ± 95% CI]; p = 0.12) nor hypoxia, but did favor gaseous exchange in normoxia (0.27 ± 0.26 [estimate ± 95% CI]; p = 0.04). After accounting for variation associated with order, family, and species, a phylogenetic model reflected that metabolic rate exhibited a significant, non-zero increase of 8.13% (± 3.48 95% CI; p < 0.0001) per °C increase in temperature. These data represent the first meta-analytic attempt to resolve the controversies surrounding the merit of adaptive hypotheses in insects.

Profiles of telomeric repeats in Insecta reveal diverse forms of telomeric motifs in Hymenopterans.

Telomeres consist of highly conserved simple tandem telomeric repeat motif (TRM): (TTAGG)n in arthropods, (TTAGGG)n in vertebrates, and (TTTAGGG)n in most plants. TRM can be detected from chromosome-level assembly, which typically requires long-read sequencing data. To take advantage of short-read data, we developed an ultra-fast Telomeric Repeats Identification Pipeline and evaluated its performance on 91 species. With proven accuracy, we applied Telomeric Repeats Identification Pipeline in 129 insect species, using 7 Tbp of short-read sequences. We confirmed (TTAGG)n as the TRM in 19 orders, suggesting it is the ancestral form in insects. Systematic profiling in Hymenopterans revealed a diverse range of TRMs, including the canonical 5-bp TTAGG (bees, ants, and basal sawflies), three independent losses of tandem repeat form TRM (Ichneumonoids, hunting wasps, and gall-forming wasps), and most interestingly, a common 8-bp (TTATTGGG)n in Chalcid wasps with two 9-bp variants in the miniature wasp (TTACTTGGG) and fig wasps (TTATTGGGG). Our results identified extraordinary evolutionary fluidity of Hymenopteran TRMs, and rapid evolution of TRM and repeat abundance at all evolutionary scales, providing novel insights into telomere evolution.

A Review of Alternative Management Tactics Employed for the Control of Various Cockroach Species (Order: Blattodea) in the USA.

Effective control of domestic and peridomestic cockroaches requires integrated approaches that emphasize concurrent use of chemicals with alternative control tactics. An integrated pest management (IPM) approach is particularly justified in environments where satisfactory cockroach control cannot be achieved due to multiple factors including development of insecticide aversion and resistance in some cockroach species, and poor sanitation or structural issues that foster infestations. While a flurry of research effort has been devoted to study alternative tactics for cockroach control, only a few of them have been evaluated in the context of IPM programs. This review focuses on examining studies on alternative tactics that are proven efficacious, economical, and logistically feasible for their inclusion in IPM programs for important domestic and peridomestic cockroaches in the USA. Management programs that educate the public on cockroach biology, behavior, and the importance of sanitation; use of traps to monitor infestation levels; apply targeted low impact insecticides such as baits, have demonstrated a greater success for effective and sustainable control of cockroaches when compared to an insecticide-only approach. Incorporation of other alternative control methods to IPM programs will require more applied research that validates their use in real-world scenarios and demonstrates their cost-effectiveness.

Fumigant toxicity of essential oils to the German cockroach (Dictyoptera: Blattellidae).

The fumigant toxicity of 12 essential oil components [carvacrol, 1,8-cineole, trans-cinnamaldehyde, citronellic acid, eugenol, geraniol, S-(-)-limonene, (-)-linalool, (-)-menthone, (+)-alpha-pinene, (-)-beta-pinene, and thymol] to adult male, adult female, gravid female, and large, medium, and small nymphs of the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), was determined. 1,8-Cineole was the most toxic essential oil component to adult males and females, gravid females, and large nymphs, with LC50 values of 6.8, 8.4, 5.3, and 11.4 mg/liter air at 24 h, respectively. (-)-Menthone and carvacrol were the most toxic essential oil components to medium and small nymphs, with LC50 values of 9.0 and 3.6 mg/liter air at 24 h, respectively. Citronellic acid was the least toxic essential oil component to all stages of the German cockroach. There was not a consistent relationship between body mass and toxicity; the susceptibility of the stages differed for each oil. LC50 values of all stages were correlated negatively with vapor pressure and positively with molecular weight of the essential oil components. The most toxic essential oil components to the majority of cockroach stages were cyclic aliphatic hydrocarbons [1,8-cineole, (-)-menthone, (+)-alpha-pinene, (-)-beta-pinene, and S-(-)-limonene]. Ring size and the presence of a carbonyl functional group also may have contributed to the toxicity of the compounds. Citronellic acid had no effect on ootheca hatch (100% hatch), whereas (-)-menthone had the greatest effect on ootheca hatch (73% hatch). Percentage of hatched oothecae decreased linearly with increasing concentration for (-)-menthone, S-(-)-limonene, (+)-alpha-pinene, and (-)-beta-pinene. No essential oil component prevented ootheca hatch, suggesting that multiple treatments would be required in the field to eliminate infestations.

Topical toxicity of essential oils to the German cockroach (Dictyoptera: Blattellidae).

The toxicity of 12 essential oil components [carvacrol, 1,8-cineole, trans-cinnamaldehyde, citronellic acid, eugenol, geraniol, S-(-)-limonene, (-)-linalool, (-)-menthone, (+)-alpha-pinene, (-)-beta-pinene, and thymol] to adult male; adult female; gravid female; and large, medium, and small nymphs of the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), was determined. Thymol was the most toxic essential oil component to adult males, gravid females, and medium nymphs, with LD50 values of 0.07, 0.12, and 0.06 mg per cockroach, respectively, trans-Cinnamaldehyde was the most toxic essential oil component to adult females, large nymphs, and small nymphs, with LD50 values of 0.19, 0.12, and 0.04 mg per cockroach, respectively. (+)-alpha-Pinene was the least toxic essential oil component to all stages of the German cockroach. The most frequently occurring susceptibility ranking for the stages was small nymphs > medium nymphs > adult males > large nymphs > gravid females > adult females. Adult females were the least susceptible to the essential oils, so they will be the determining factor when considering a rate for field application. Toxicity was positively correlated with essential oil component density and boiling point; however, there was no significant correlation between toxicity and lipophilicity. The effect of essential oil components on ootheca hatch was also investigated. S-(-)-limonene had the least effect on ootheca hatch, with 35.21 (mean) nymphs hatching per ootheca. (-)-menthone had the greatest effect on ootheca hatch with 20.89 nymphs hatching per ootheca The numbers of nymphs hatching from each ootheca generally declined as dose increased. No essential oil component completely prevented ootheca hatch suggesting that multiple treatments might be required in the field to prevent reinfestation.

Effects of indoxacarb concentration and exposure time on onset of abnormal behaviors, morbundity, and death in eastern subterranean termite (Isoptera: Rhinotermitidae).

Onset of abnormal behaviors, morbundity, and death was evaluated in eastern subterranean termites, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae), exposed to several concentrations (45, 90, 135, and 180 ppm) of indoxacarb and to several (5, 10, 20, 40, 80, and 160 min) exposure periods. Abnormal behaviors, morbundity, and death occurred in a predictable sequence: disorientation, ataxia, and morbundity followed by death. In general, higher concentrations and longer exposure periods resulted in faster onset of abnormal behaviors, morbundity, and death. The average onset time of abnormal behaviors, morbundity, and death was faster for groups of termites compared with individuals exposed to similar concentrations and periods of contact. The importance of onset times of abnormal behaviors as another important measure of the toxicity of slow-acting toxicants is discussed.