Nutritional status and insecticide tolerance in German cockroaches (Orthoptera: Blattellidae).

The interrelationship of two extrinsic factors-nutrition and pesticide exposure-was studied in German cockroaches, Blattella germanica (L.). Amount of dietary protein had no effect on susceptibility of male German cockroaches to propoxur and chlorpyrifos; however, the source of protein produced significant changes in insecticide susceptibility. Increased total body lipids, carbohydrates, and uric acid may have resulted in increased tolerance to these insecticides. Three days of food or water deprivation (or both) caused significant differences in susceptibility to chlorpyrifos and propoxur.     

Comparisons of toxic baits for controlling the cockroach, Blattella germanica: attractiveness and feeding stimulation

Female German cockroaches, Blattella germanica (L.) (Dictyoptera: Blattellidae) and nymphs (stages 1, 3 and 6) were used to test the attractiveness and the feeding stimulation of several commercial gel formulations of insecticide food baits in laboratory binary choice tests. The four toxic gel baits tested were: 'Avert' (0.05% abamectin=avermectin B1), 'Drax' (33.3% boric acid), 'Goliath' (0.05% fipronil) and 'Maxforce' (2.15% hydramethylnon). The attractiveness of a bait was estimated by the number of cockroaches that chose it first, and by their tendency to change to it secondarily. Feeding stimulation was estimated by the mean duration of feeding bouts and total duration of food intake. Variability of these factors was assessed in relation to age of cockroaches and to age of baits. With a few exceptions, cockroach age did not affect performance in any of these tests. Attractiveness to B. germanica ranked 'Goliath' gel higher than 'Avert', 'Drax' and 'Maxforce' gels, whether or not the active ingredient fipronil was present in 'Goliath' gel. Feeding stimulation ranked 'Avert' and 'Maxforce' gels higher than 'Goliath' gel, and 'Drax' gel was inferior. With ageing up to 3 months, the feeding stimulation power of 'Goliath' and 'Maxforce' gels increased, whereas that of 'Avert' fluctuated. Assuming that all types of bait effectively kill cockroaches once ingested, these results illustrate the importance of behavioural observations on bait efficiency and show that ranking of these different food baits varies in relation to the parameter analysed.     

Haemolymph sugar levels in a nectar-feeding ant: dependence on metabolic expenditure and carbohydrate deprivation

In nectar-feeding insects, sugars are an important source of fuel and energy storage. Here, we analyzed the haemolymph sugar levels in foragers of the ant Camponotus rufipes trained to collect nectar from an artificial feeder, and their dependence on the metabolic rate during feeding. The main sugar found was trehalose, followed by glucose and traces of fructose and sucrose. In foragers, trehalose level was independent of their activity and metabolic rate while feeding. Carbohydrate deprivation of the colony had a strong effect on the haemolymph sugar levels of workers, with a significant decrease in trehalose and glucose with increasing starvation. We also found a correlation between haemolymph sugar levels and behavioral states, with immobile workers having higher trehalose and fructose levels than active ones. It is suggested that under food deprivation, inside-nest workers initially stay completely immobile as a strategy to save energy, and only become active and start to search for food when the trehalose levels decrease even more. Based on a conservative estimation, well-fed ants could travel up to 500 m, or spend more than 20 h inactive at 25°C, using only the energy provided by the haemolymph trehalose, before reaching the levels found in starved nest-mates.     

Genetic studies of a behavioral mutant,glucose aversion,in the German cockroach (Dictyoptera: Blattellidae)

Glucose aversion(Glu) is a naturally occurring behavioral mutant of the German cockroach,Blattella germanica. Earlier work suggested thatGlu is a semidominant autosomal trait. Further study was undertaken to place the mutant gene in the linkage map of the species and expand the information on its genetic basis. Linkage was investigated in test crosses with morphologic markers for 7 of the 11 autosomal linkage groups. Assays for amounts of glucose ingested per individual confirmed the expected low consumption ofGlu heterozygotes(Glu/+) and that continuous selection pressure on the parental strain had resulted in near- and probably complete homozygosity forGlu. Glu genotypes were identified by means of a discriminating ingestion that separated heterozygotes from wild type(Glu+). Variations in expression indicate that genetic factors influence food consumption inB. germanica. Positive results were obtained in linkage tests ofGlu with ruby eye(ru), indicating that theGlu locus lies in linkage group VIII (chromosome 9), a group notable for mutants that apparently result in the expression of latent, highly primitive development pathways.     

A functional<Emphasis Type="Italic"> gltB</Emphasis> gene is essential for utilization of acidic amino acids and expression of periplasmic glutaminase/asparaginase (PGA) by<Emphasis Type="Italic"> Pseudomonas putida</Emphasis> KT2440

Pseudomonas putida KT2440, a root-colonizing fluorescent pseudomonad, is capable of utilizing acidic amino acids (Asp and Glu) and their amides (Asn and Gln) as its sole source of carbon and nitrogen. The uptake of Gln and Asn is facilitated by a periplasmic glutaminase/asparaginase (PGA), which hydrolyses Asn and Gln to the respective dicarboxylates. Here, we describe transposon mutagenesis of P. putida KT2440 with a self-cloning promoter probe vector, Tn5-OT182. Transconjugants defective in Glu-mediated PGA induction were selected for further studies. In most clones the transposon was found to have integrated into the gltB gene, which encodes the major subunit of the glutamate synthase (GOGAT). The transconjugants were nonmotile, no longer showed a chemotactic response towards amino acids, and could not survive prolonged periods of starvation. The acidic amino acids and their amides supported growth of the transconjugants only when supplied together with glucose, suggesting that the gltB-mutants had lost the ability to utilize amino acids as a carbon source. To confirm that gltB inactivation was the cause of this phenotype, we constructed a mutant with a targeted disruption of gltB. This strain behaved like the clones obtained by random mutagenesis, and failed to express not only PGA but also a number of other Glu-induced proteins. In contrast to wild-type cells, the gltB ^- strain accumulated considerable amounts of both Glu and Gln during long-term incubation.Communicated by A. Kondorosi     

Density-dependent natural selection does not increase efficiency

Summary Populations ofDrosophila melanogaster kept at high population density (K-selected) for 125 generations have higher larval viability than populations kept at low densities (r-selected) when both are raised under crowded conditions. In additionK-selected adults that emerge from crowded cultures are larger than theirr-selected counterparts. These differences cannot be explained by differences in efficiency of food use. The minimum food required for successful pupation is actually greater in theK-selected populations. I conjecture that there may be a trade-off between minimum food requirements and competitive ability, which has changed substantially in theK-selected populations. The possibility thatK-selected larvae can dig more more deeply and gain access to unused food is examined and rejected as a possible explanation of the viability differences. Evidence is provided supporting the hypothesis that the differences in viability may be due to an increased tendency of theK-selected larvae to pupate off the surface of the medium.     

Description of the basic features of parent‐offspring stomodeal trophallaxis in the subsocial wood‐feeding cockroach Salganea esakii (Dictyoptera,Blaberidae, Panesthiinae)

In subsocial xylophagous cockroaches it is thought that parental feeding is important for the survival and growth of the altricial offspring, but the details of parental feeding in these groups are poorly known. We observed stomodeal (oral) trophallaxis between parents and the 2nd or 3rd instars of the wood‐feeding cockroach Salganea esakii Roth, and here report basic features of trophallaxis in young families. Both the female and male parents fed young nymphs with stomodeal food, and there was no difference in the frequency of the behavior between parental sexes. Up to three nymphs could be fed simultaneously during a single trophallactic event. Adults occasionally rejected contact with nymphs by blocking them with their forelegs. Nymphs utilized trophallactic food from parents more frequently than feeding independently on wood pieces or fecal pellets. Trophallaxis between sibling nymphs was never observed. These results suggest that the 2nd and 3rd instar nymphs rely on the stomodeal substances provided by their parents, and that provisioning is an essential component of subsocial behavior in biparental wood‐feeding cockroaches.     

Differential consumption of baits by pest blattid and blattellid cockroaches and resulting direct and secondary effects

Consumption was measured of three commercially available cockroach gel baits (0.01 and 0.05% fipronil and 0.6% indoxacarb) by two pest blattellid (German cockroach, Blattella germanica L., and brownbanded cockroach, Supella longipalpa Fabricius) and three pest blattid [oriental cockroach, Blatta orientalis L., American cockroach, Periplaneta americana L., and smokybrown cockroach, Periplaneta fuliginosa (Serville)] species (Dictyoptera), and direct and secondary effects were quantified. All three baits were greatly preferred for consumption over dog food; however, virtually all consumption (ca. 98%) by pest blattids was gel baits containing sugar feeding stimulants and water. Pest blattid greater preference for gel baits was probably due to their greater need for nutrients in baits due to their greater cuticular water permeability and higher metabolism than the pest blattellids. Brownbanded cockroaches had lowest percentage gel bait selection. Pest blattellids consumed greater amounts of bait per g body weight than pest blattids. Cockroaches consumed more active ingredient than needed to cause mortality; however, based on bait consumption, a 30‐g tube of gel bait potentially killed from 394 to 6 966 adult cockroaches, depending on species. Mortality for all cockroach species was faster for adults (≥3 days) than for nymphs (≥7 days); however, most brownbanded cockroaches exposed to indoxacarb survived despite consuming 1.5‐ to >3‐fold more than other baits, suggesting low enzyme production by brownbanded cockroaches and consequently lower conversion of indoxacarb into its toxic form. Besides direct mortality, German cockroaches died from indirect effects: exposure to debris from other cockroaches that had direct access to the gel baits or bait contact without ingestion. Although maximization of bait consumption is important, factors that enhance secondary mortality and contact toxicity should also be considered.     

Local enhancement promotes cockroach feeding aggregations

Communication and learning from each other are part of the success of animal societies. Social insects invest considerable effort into signalling to their nestmates the locations of the most profitable resources in their environment. Growing evidence also indicates that insects glean such information through cues inadvertently provided by their conspecifics. Here, we investigate social information use in the foraging decisions by gregarious cockroaches (Blattella germanica L.). Individual cockroaches given a simultaneous choice in a Y-olfactometer between the odour of feeding conspecifics and the mixed odour of food plus non-feeding conspecifics showed a preference for the arm scented with the odour of feeding conspecifics. Social information (the presence of feeding conspecifics) was produced by cockroaches of all age classes and perceived at short distance in the olfactometer arms, suggesting the use of inadvertently provided cues rather than signals. We discuss the nature of these cues and the role of local enhancement (the selection of a location based on cues associated with the presence of conspecifics) in the formation of feeding aggregations in B. germanica. Similar cue-mediated recruitments could underpin a wide range of collective behaviours in group-living insects.     

Factors restricting the feeding of the cabbage stem flea beetle (Psylliodes chrysocephala)

The feeding acceptability of 40 different plants to Psylliodes chrysocephala L. (Coleoptera: Chrysomelidae) was determined using leaf disc consumption tests for the adult, and stem or petiole penetration tests for the larvae. Only plants that contained glucosinolates were accepted as food, but addition of the glucosinolate sinigrin to rejected food plants did not make them acceptable to adults. Of the 34 plants that contained glucosinolates, nine were either totally or mostly rejected. Solvent extracts of the rejected plants applied to oilseed rape inhibited feeding by adults. The feeding of P. chrysocephala within the group of plants tested is influenced by the presence or absence of glucosinolates, which may act as feeding stimulants, and other, unidentified chemicals which act as feeding inhibitors.     

The effect of deprivation on the microstructure of feeding by the Tobacco hornworm caterpillar

An automated device was used to examine, in detail, feeding on disks of wheat germ medium by fifth-instar Manduca sextacaterpillars. Comparisons were made between some animals which had ad libitum access to food at all times and others which were deprived of food for 1–5 h before being tested. Feeding patterns of both groups indicated regulation of feeding both between and within meals. Deprived animals ate more during their first meal than did nondeprived animals chiefly by increasing (a) the number of chewing bouts (and thus the meal duration) and (b) the bite frequency. Calculations indicated that the deficit caused by deprivation was made up during the first meal. However, deprived animals continued to eat more than nondeprived ones in subsequent feeding also. Passage of food through the gut was examined by dissecting out the contents of each region of the gut at various times after a colored test meal. Food passed through the foregut directly into the anterior part of the midgut. It stayed in the middle third of the midgut longer than in the anterior and posterior thirds, and the first pellet resulting from the test meal appeared 4 h after the meal. The following mechanisms of feeding regulation are proposed: (a) volumetric feedback mediated by stretch receptors of the foregut and anterior third of the midgut which terminates meals; (b) the development and subsequent reduction of satietyspecific behaviors mediated either by stretch receptors or by some other means which, e.g., allow the next meal to begin; and (c) metabolites whose levels drop during deprivation, triggering a series of events which lead to the excess feeding observed.     

Differential inputs from chemosensory appendages mediate feeding responses to glucose in wild-type and glucose-averse German cockroaches, Blattella germanica

Glucose is a universal phagostimulant in many animal species, including the cockroach Blattella germanica. However, some natural populations of B. germanica have been found that are behaviorally deterred from eating glucose. In dose-response studies, glucose was a powerful phagostimulant for wild-type cockroaches, but it strongly deterred feeding in a glucose-averse strain. Both strains, however, exhibited identical dose-response curves to other phagostimulants and deterrents. As a lead to electrophysiological and molecular genetics studies to investigate the mechanisms that underlie glucose-aversion, we used 2 assay paradigms to delineate which chemosensory appendages on the head contribute to the reception of various phagostimulatory and deterrent chemicals. Both simultaneous dual stimulation of the antenna and mouthparts of the insects and 2-choice preference tests in surgically manipulated insects showed that the glucose-averse behavior could be elicited through the gustatory systems of the antennae and mouthparts. The paraglossae alone were sufficient for maximum sensitivity to both phagostimulants and deterrents, including glucose as a deterrent in the glucose-averse strain. In addition to the paraglossae, the labial palps were more important than the maxillary palps in the reception of deterrents (caffeine in both strains and glucose in the glucose-averse strain). The maxillary palps, on the other hand, played a more important role in the reception of phagostimulants (fructose in both strains and glucose in the wild-type strain). Our results suggest that distinct inputs from the chemosensory system mediate opposite feeding responses to glucose in the wild-type and glucose-averse strains.     

Summer torpor in African woodland dormiceGraphiurus murinus (Myoxidae: Graphiurinae)

We determined the effect of food availability (presence/absence) and ambient temperature (25/10°C) on daily energy expenditure and the use of activity and torpor in summer-acclimated captiveGraphiurus murinus. Daily energy expenditure declined logarithmically with duration of food deprivation at a mean rate of 11 and 31% per day at 25 and 10°C, respectively. The incidence of torpor in the presence of food at 25°C was low (one in seven individuals) and increased on a single day's exposure to 10°C and with duration of food deprivation. Use of torpor was highest during the day, varied between individuals, and torpor bouts of greater than 24h duration were not noted. With food deprivation, individuals at 25°C initially responded by reducing activity but remained euthermic while the same individuals at 10°C responded by increasing their use of torpor during the light period; this difference in response probably reflects a difference in the relative energetic benefits of torpor at different temperatures.     

Effect of food deprivation on the ambulatory movement of the Colorado potato beetle,Leptinotarsa decemlineata

Modification of dispersal behaviour is a common response of insects to food and water deprivation. The literature suggests that different insects respond with different strategies: changing walking parameters, switching dispersal mode (walking to flight or vice versa), or changing the host searching path. The goal of this study was to add to the limited literature on the subject by investigating, whether the walking parameters of adult male Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), change in response to food and water deprivation. Observations on the distance walked, the travel speed, and the frequency of walking bouts were carried out in laboratory arenas using motion monitoring equipment. Summer and overwintered beetles were exposed to short starvation periods (2, 4, 8, 24 h) and two ranges of long starvation periods (1, 2, 4, 8 days and 1, 2, 4, 8, 16, and 32 days). Only the longest food deprivation periods of 16 and 32 days significantly reduced the walking distance, speed, and frequency of walking bouts of summer beetles. No changes were observed with overwintered beetles. The tolerance of the beetles without access to water to the different periods of food deprivation was similar to that for beetles with water except after a starvation period of 32 days, when the travel speed of summer beetles was significantly reduced by 33%. The absence of increased walking parameters found in this study and earlier observations of increased flight frequency suggest that the strategy of summer beetles will be to change the dispersal mode from walking to flight and/or to change the walking host searching path. The same results of this study and earlier observations of a decrease in the mean frequency of daily flights suggest that the strategy of overwintered L. decemlineata, exposed to food deprivation, will be to change the host search walking path rather than the walking parameters themselves.     

Separating food and water deprivation in locusts: effects on the patterns of consumption, locomotion and growth

Abstract. In a factorial experiment, fifth-instar Locusta migratoria (L.) (Orthoptera: Acrididae) were given either dry food (lyophilized grass) and drinking water, food only, water only, or neither food nor water.Food consumption and insect weight were measured daily, and the behaviour of each locust was recorded for 5 h on each of four consecutive days and for 2.5 h on the fifth.Consumption declined progressively in locusts given food only, and those given water only were not observed to drink after the first day of food deprivation.The decline in food consumption on the first day was accounted for by a decrease in the average duration of feeds, which remained constant thereafter.The further decline in consumption over subsequent days was due to a progressive decline in the number of feeds.Although food availability did not slow weight loss relative to locusts given neither food nor water, the availability of water without food did.The proportion of time locomoting increased in all deprivation treatments, but the pattern of change across the five observation days differed markedly between treatments.Locusts given food but no water increased locomotion from 20% of the time budget (the value for controls) to 30% on the first day of deprivation, and by the second day had reached a plateau of approximately 65%.which was maintained until the experiment was terminated on day 5.In contrast, locusts given water but no food approached the 65% level of locomotion on the first day, which was stutistically greater than the 55% observed in those deprived of both food and water.This increase was due both to an increase in the number of locomotion bouts initiated and an increase in the average duration of locomotion bouts.On the second and third days, all deprivation treatments maintained locomotion at around 65%.By day 4, locomotion had decreased to approximately 15% in locusts deprived of both food and water, but not in those deprived of food only or water only.Unlike those given only food, locusts given only water showed a reduction in locomotion of c. 15% on the fifth day.     

Diet specialization in an extreme omnivore: nutritional regulation in glucose‐averse German cockroaches

Organisms have diverse adaptations for balancing dietary nutrients, but often face trade‐offs between ingesting nutrients and toxins in food. While extremely omnivorous cockroaches would seem excluded from such dietary trade‐offs, German cockroaches (Blattella germanica) in multiple populations have rapidly evolved a unique dietary specialization – an aversion to glucose, the phagostimulant in toxic baits used for pest control. We used factorial feeding experiments within the geometric framework to test whether glucose‐averse (GA) cockroaches with limited access to this critical metabolic fuel have compensatory behavioural and physiological strategies for meeting nutritional requirements. GA cockroaches had severely constrained intake, fat and N mass, and performance on glucose‐based diets relative to wild‐type (WT) cockroaches and did not appear to exhibit digestive strategies for retaining undereaten nutrients. However, a GA × WT ‘hybrid’ had lower glucose aversion than GA and greater access to macronutrients within glucose‐based diets – while still having lower intake and survival than WT. Given these intermediate foraging constraints, hybrids may be a reservoir for this maladaptive trait in the absence of positive selection and may account for the rapid evolution of this trait following bait application.     

Evaluations on the Lethal, Choice and Secondary Effects of Four Insecticidal Baits against the German Cockroach (Blattaria, Blattellidae)

ABSTRACT The laboratory studies were carried out for evaluating control effects of four commercial insecticidal baits such as two different hydramethylnon [2.0%(AI)] products (DBK^® and Combat‐Gold^®), fipronil [0.05 %(AI)] (Combat‐Power^®) and (0.6% chlorpyrifos [0.6%(AI)] (Raid‐Roachbait^®) against German cockroaches (Blattella germanica). The control rates of four kinds of toxic baits were all 100.0% mortality of German cockroaches in 5 days after treatment. The results of chlorpyrifos and fipronil brought 100.0% mortalities in 2 to 3 days after treatment, respectively. After 3 day treatment, there was no significant difference of control effect among the four toxic baits. As a result of this study, fipnonil and chlorpyrifos showed faster killing action against German cockroaches than the two hydramethylnon formulation products. In the choice test, DBK^® (hydramethylnon) (average 17.0 ind.) significantly attracted more German cockroaches than Combat‐Gold^® (hydramethylnon) (avg. 7.0 ind.), Combat‐Power^® (fipronil) (avg. 5.3 ind.) and Raid‐Roachbait^® (chlorpyrifos) (avg. 3.3 ind.). The difference in attraction effects came 10 minutes after treatment. In order to evaluate the secondary killing effect of toxic baits by coprophagy against adult Blattella germanica, the comparative test was carried out. The adult mortality rates were significantly different among the four toxic baits showing 86.7% mortality for fipronil, 60.0% for hydramethylnon (DBK^®), 30.0% for chlorpyrifos, and below 13.3% for hydramethylnon (Combat‐Gold^®) in 6 days. During the first 12 days, fipronil showed the highest mortality rate (90.0%), followed by hydramethylnon (DBK^®) (60.0%). The secondary killing effect of toxic baits by coprophagy appeared in all of the baits against adult Blattella germanica.     

Prey feeding increases water stress in the omnivorous predator Dicyphus hesperus

The effects of water stress (produced by water deprivation and prey feeding) on plant feeding were investigated in the omnivorous predator Dicyphus hesperus Knight (Hemiptera: Miridae). The objective was to determine if prey feeding aggravated water deficits and thus increased plant feeding. We measured plant feeding in a factorial experiment where female D. hesperus were prepared for experiments by providing or withholding water and/or prey for 24 h. We then evaluated the amount of plant feeding on Nicotiana tabacum seedlings by the direct observation of insects at three different densities of the prey, Ephestia kuehniella eggs. The amount of plant feeding, as measured by frequency of plant feeding bouts and time spent plant feeding during observation, was significantly greater for water‐deprived individuals than for those that had been provided with water. Individuals that had been provided with prey fed on plants at a significantly higher frequency than prey‐deprived individuals at two of the prey densities used in the experiment. These results support the hypothesis that plant feeding in zoophytophagous Hemiptera facilitates prey feeding by providing water that is essential for predation.     

Laboratory and field performance of an imidacloprid gel bait against German cockroaches (Dictyoptera: Blattellidae)

An experimental 2.15% imidacloprid gel bait containing approximately 44% water was evaluated in laboratory and field studies against the German cockroach, Blattella germanica (L). In continuous exposure tests, toxicity and presumably bait consumption varied with cockroach stage, deprivation of competitive food, and temperature. The LT50 values for cockroaches provided with competitive food ranged from approximately 0.9 h for adult females to 190 h for small nymphs. The LT50s for cockroaches not provided competitive food ranged from approximately 1.7 h for adult females to approximately 31 h for adult males. The LT50s decreased exponentially with temperature between 10 and 30 degrees C. Even though the bait was significantly more repellent (approximately 38%) than an untreated control (approximately 14%) when tested in Ebeling choice boxes, performance index values were positive and increased to nearly 100 (indicating high mortality and low repellency) after 14 d. When applied at 15-45 g per kitchen, the bait significantly reduced German cockroach trap catch in infested homes during a 4-wk period. There was a approximately 50% reduction after 1 wk and approximately 80% reduction 4 wk after treatment.     

Feeding behavior ofLemur catta andLemur fulvus

The feeding behavior of two sympatric species of lemurs, Lemur cattaand Lemur fulvus,was studied in an enclosure simulating a natural habitat at the Duke University Primate Center. L. fulvusspent less time feeding during the day than L. catta.But the former species ate more fruit and had longer feeding bouts on preferred food items than L. catta.They also had a shorter food passage time than L. cattaand their choice of resting places was more influenced by food distribution. Furthermore, the two lemur species ate parts of different plant species and showed different reactions to chemical plant components. According to these results, L. fulvusis a more conservative feeder than L. catta.These interspecific differences in feeding behavior may be one of a number of differences that allow the two species to coexist. In allopatry, however, L. fulvusmay also adopt feeding patterns similar to those of L. catta.But L. cattawas never found to change its feeding strategies in different areas. It may be this option of L. fulvusto adopt different feeding strategies in different situations that allows this species to have the widest range of all Malagasy lemurs. Duke University Primate Center Publication No. 259.