Adult house flies (Musca domestica L.) are often a major pest at livestock facilities, where oviposition occurs on decomposing organic matter, such as manure. Some potential foods that adult house flies might consume on dairy farms were examined. Relative to when they were given water alone, survival of males and females was greater when they were given water along with liquid whole milk, formulated calf feed, or corn silage, or finely milled sorghum or soy, or buckwheat inflorescences. However, survival was significantly lower with these foods than with sucrose, although not significantly so for males with milk. There was little to no survival advantage when flies were given water along with milled hominy, wet spent brewers grain, or manure than with water alone. Both males and females spent significant time with their labellum in contact with corn silage, dandelion inflorescences, and buckwheat inflorescences, but little time with their labellum contacting manure or white clover inflorescences. Egg production was not increased by access to water along with buckwheat inflorescences or corn silage relative to sucrose; but egg production was increased by access to liquid whole milk. Reaching mature vitellogenesis stages was improved by prior exposure to water and sucrose solution along with a mixture of dry sucrose, milk, and yolk, or along with calf manure or formulated calf feed, but not with milled soy, sorghum, or hominy, or with wet spent brewers grain or citrus pellets. The diet including sucrose-milk-yolk resulted in the most females reaching mature vitellogenesis stages.

House flies, Musca domestica L., are pests at livestock facilities. House fly numbers are controlled mainly by manure management and chemical controls, like use of toxic baits. Some toxic baits contain denatonium benzoate as a bittering agent, to avoid poisoning of children. House fly behavioral response to denatonium benzoate was examined, using 2 different diluents, sucrose solution or orange juice. Response of flies to quinine and sucrose octaacetate, 2 other bittering agents, was also examined in sucrose. Sucrose is the sweetener in commercially available toxic house fly baits. The proboscis extension response of both male and female flies was significantly reduced by addition of 1,000 ppm of denatonium benzoate to sucrose. Response in males was also reduced at 100 ppm. Consumption of sucrose by both male and female flies was reduced by addition of 100, 500, and 1,000 ppm of denatonium benzoate, but consumption by males was also reduced at 10 ppm. Addition of sucrose octaacetate had no detectable effect on consumption of sucrose at 100, 500, or 1,000 ppm. In contrast, addition of quinine reduced consumption by both male and female flies in all tested concentrations. In orange juice, 10 ppm of denatonium benzoate is often avoided by children. With orange juice, fly proboscis extension response patterns were the same for both sexes, with a reduction at 1,000 ppm of denatonium benzoate. Orange juice consumption by flies was reduced significantly at 1,000 ppm of denatonium benzoate for females but not at any of the concentrations tested for males.

The house fly, Musca domestica L., is a vector of pathogens. When sanitation measures fail to control fly populations, pesticides are often used. Fungal biopesticides have been suggested as another tool in fly control. Our study investigated whether inhibitors of eicosanoid biosynthesis (EBI), and presumably of immunity, combined with the fungal biopesticide BotaniGard ES is a feasible option for a new biopesticide formulation. The EBIs tested were dexamethasone, naproxen, and esculetin. An insecticide-susceptible and an insecticide-resistant house fly strain were tested. Compared to a control sugar cube with no EBI and no BotaniGard ES, both strains spent a shorter duration at sugar cubes with fungus alone and with fungus combined with naproxen; flies from the susceptible strain spent a shorter duration at cubes with fungus combined with dexamethasone; and flies from the resistant strain spent a shorter duration at cubes with fungus combined with esculetin. Both strains, whether exposed to fungus, fungus with dexamethasone, or fungus with naproxen, had higher mortality risk compared to a control. With or without injection of an EBI, immersion in a fungal solution increased mortality. However, with CAR21 flies, mortality was greater with the naproxen injection than with dexamethasone- or esculetin injection with the fungal immersion. Due to no greater mortality for both strains for all EBI and BotaniGard ES combinations compared to BotaniGard ES alone, it is not recommended that dexamethasone, esculetin, or naproxen be used in conjunction with BotaniGard ES for house fly control.

The house fly, Musca domestica, is a cosmopolitan filth fly pest common in agricultural and urban areas where decaying organic matter is available for larval development. Adult M. domestica are nuisances and vectors of disease. When sanitation, screens, and sticky fly strips fail to control house fly populations, insecticide baits are often used. The use of baits can lead to the evolution of resistance, including not only physiological resistance to the toxicant but also behavioural resistance to the phagostimulant and to the toxicant. Here, the non-nutritive sweeteners neotame and allulose were examined for their suitability as replacement phagostimulants in insecticidal baits for house flies. Suitability was assessed using proboscis extension response (PER) and consumption experiments. Allulose was further examined for insecticidal activity. Dry neotame elicited no PER, and it would not easily go into solution, so it was not examined in solution. Both in dry form and in solution, allulose elicited some PER and consumption, but only half or less of what sucrose or fructose elicited. Flies fed allulose alone had lower survival rates than flies fed sucrose alone. When given both allulose and sucrose, flies survived at similar rates to flies only fed sucrose. Neotame is not recommended as a replacement phagostimulant in bait formulations. Allulose alone is not recommended as a replacement phagostimulant. It remains to be seen whether combining allulose with sucrose as the phagostimulant in baits would result in as much bait consumption as just sucrose. If so, it might be worth testing whether the combination could serve as a rotational phagostimulant to prevent behavioural resistance to sucrose from evolving.

The insect equivalent of taste buds are gustatory sensilla, which have been found on mouthparts, pharynxes, antennae, legs, wings, and ovipositors. Most gustatory sensilla are uniporous, but not all apparently uniporous sensilla are gustatory. Among sensilla containing more than one neuron, a tubular body on one dendrite is also indicative of a taste sensillum, with the tubular body adding tactile function. But not all taste sensilla are also tactile. Additional morphological criteria are often used to recognize if a sensillum is gustatory. Further confirmation of such criteria by electrophysiological or behavioral evidence is needed. The five canonical taste qualities to which insects respond are sweet, bitter, sour, salty, and umami. But not all tastants that insects respond to easily fit in these taste qualities. Categories of insect tastants can be based not only on human taste perception, but also on whether the response is deterrent or appetitive and on chemical structure. Other compounds that at least some insects taste include, but are not limited to: water, fatty acids, metals, carbonation, RNA, ATP, pungent tastes as in horseradish, bacterial lipopolysaccharides, and contact pheromones. We propose that, for insects, taste be defined not only as a response to nonvolatiles but also be restricted to responses that are, or are thought to be, mediated by a sensillum. This restriction is useful because some of the receptor proteins in gustatory sensilla are also found elsewhere.

This review summarizes which body parts have taste function in which insect taxa. Evidence of taste by mouthparts, antennae, and tarsi is widespread. Mouthparts that commonly have taste function are the labium, including the labella and labial palps, the maxillae, including the galeae and maxillary palps, the inner surface of the labrum or clypeolabrum of chewers, and inside the precibarium/cibarium of hemipterans, which have piercing-sucking mouthparts. Tasting with mandibles has not been found, and tasting with the hypopharynx is seldom reported. Use of the antennae appears uncommon among fly species, but common among species of lepidopterans, hymenopterans, beetles, and bugs. Although tasting with legs, especially tarsi, is reported mostly for fly and lepidopteran species, there is also evidence of it for multiple species of beetles, grasshoppers, and hemipterans, and one species of a roach, an ant, and a bee. Ovipositor taste function has been supported for some species of flies, lepidopterans, hymenopterans, orthopterans, and odonates. Taste by wings has been much less studied, but has been documented in a few fly species. Taste remains unstudied for any species or any body parts of Archaeognatha, Dermaptera, Mantodea, Mecoptera, Phasmatodea, Megaloptera, Neuroptera, Phthiraptera, Psocoptera, Siphonaptera, as well as Raphidioptera, Strepsiptera, Embioptera, Notoptera, and Zoraptera. Across holometabolous insects, larvae have not often been examined, the exception being some species of lepidopterans, flies, and beetles. Taste studies of antenna and legs are uncommon for even lepidopteran and beetle larvae.

Most parasitoid wasps parasitize herbivorous insects, so nectar from flowers is readily available. However, parasitoid wasps are also an important component of the rich invertebrate communities at livestock facilities in large accumulations of manure, where flowers are largely absent. Little is known about adult parasitoid diet and nutrition in these communities. The present study examined this in Spalangia cameroni Perkins, a pupal parasitoid of filth flies. Like many parasitoid wasps, S. cameroni feed on host fluids, and in the laboratory readily feed on honey or a sucrose solution, which increases their longevity. Here adult longevity in the presence of six potential food sources, bovine manure, sorghum silage, bovine milk, buckwheat inflorescence (Polygonaceae), sweet alyssum inflorescence (Brassicaceae), or dandelion inflorescence (Asteraceae), was compared to that with water or honey. Only parasitoids given buckwheat lived as long as parasitoids given honey, and parasitoids given honey or buckwheat lived longer than parasitoids given water. Parasitoids readily ate buckwheat nectar, avoiding pollen grains. Diet affected the amount of free sugars, glycogen, and lipids in complex ways. Compared to parasitoids that were given just water, parasitoids with access to honey or sucrose had higher sugar and glycogen levels, but not detectably higher lipid levels. Access to buckwheat had no detectable effect on a parasitoid's free sugar, glycogen, or lipid levels; however, then after 4 d with just water, sugar levels were lower and glycogen levels were higher compared to parasitoids that had been given access to only water the entire time.

Foreign materials like insecticides may increase grooming in insects; and generally, grooming may be expected to reduce effects of insecticides, but this may not be the case when grooming involves the mouth and hence a risk of ingestion. To examine this, female Spalangia endius, a wasp that parasitizes filth fly pupae, were exposed to a surface coated with a low concentration of imidacloprid or not. Their mouthparts were sealed or not to determine whether sealing is a useful method for examining effects of mouth grooming. Wasps mouth-groomed more frequently while exposed to imidacloprid than when not. However, imidacloprid did not increase the number of times that a wasp groomed the rest of her body, and this was true regardless of whether or not her mouthparts were sealed. While exposed to imidacloprid, wasps spent less time locomoting only if their mouthparts were not sealed. Having been exposed to imidacloprid also decreased subsequent longevity, from 9 to 7 d. These effects of imidacloprid on grooming, locomotion, and longevity occurred despite exposure being for just 5 min and to only 2% of the amount that will be present in an area immediately after house fly baits are scattered at their recommended coverage. This is such a low amount that, with 48 h of constant exposure, mortality of these wasps is only 10%. Having mouthparts sealed decreased locomotion and longevity regardless of exposure to imidacloprid. Thus, sealing mouthparts is not useful for measuring effects of mouth grooming.

Veterinary and medical entomologists who are involved in research on pest control often need to perform dose-response bioassays and analyze the results. This article is meant as a beginner's guide for doing this and includes instructions for using the free program R for the analyses. The bioassays and analyses are described using previously unpublished data from bioassays on house flies, Musca domestica Linnaeus (Diptera: Muscidae), but can be used on a wide range of pest species. Flies were exposed topically to beta-cyfluthrin, a pyrethroid, or exposed to spinosad or spinetoram in sugar to encourage consumption. LD50 values for beta-cyfluthrin in a susceptible strain were similar regardless of whether mortality was assessed at 24 or 48 h, consistent with it being a relatively quick-acting insecticide. Based on LC50 values, spinetoram was about twice as toxic as spinosad in a susceptible strain, suggesting a benefit to formulating spinetoram for house fly control, although spinetoram was no more toxic than spinosad for a pyrethroid-resistant strain. Results were consistent with previous reports of spinosad exhibiting little cross-resistance. For both spinosad and spinetoram, LC50 values were not greatly different between the pyrethroid-resistant strain and the susceptible strain.

Filth flies cause billions of dollars of losses annually to the animal production industry. Fluralaner is a relatively new pesticide currently sold for control of fleas, ticks, and mites on companion animals and poultry. We examined the efficacy of fluralaner against three species of filth flies. Insecticide-susceptible horn flies and stable flies were tested topically. Fluralaner outperformed permethrin by >2-fold for the horn flies but underperformed permethrin by >45-fold for stable flies at 24 h. House flies were tested topically with fluralaner in comparison to permethrin at 48 h and orally with fluralaner in comparison to imidacloprid at 24 h. Topical fluralaner was 6- to 28-fold as toxic as permethrin in four pyrethroid-resistant strains and not significantly less toxic than permethrin in a susceptible strain and a mildly pyrethroid-resistant strain. There was slight cross-resistance between topically applied fluralaner and permethrin in all five insecticide-resistant strains tested. Oral fluralaner was more toxic than imidacloprid in all four house fly strains tested, 9- to 118-fold as toxic. Oral cross-resistance between imidacloprid and fluralaner was not detected, but imidacloprid resistance was not high in any of the tested strains. Fluralaner shows promise for control of horn flies and house flies.

Both the parasitoid wasp Spalangia endius Walker and the insecticide imidacloprid are used to control house flies. A recent study found that negative sublethal effects of imidacloprid on killing flies and on offspring production by this parasitoid wasp are eliminated when females have the opportunity to crawl through decaying matter. An enzyme-linked immunosorbent assay showed that the presence of decaying matter reduces the amount of pesticide on their bodies. This study examined whether this was also true for sublethal effects on mating. S. endius were exposed to a realistic concentration of imidacloprid that induces very low mortality. Then, individual parasitoids were allowed to burrow through decaying organic matter or not, followed by mating tests in the absence of decaying matter. Even after 24 h with the decaying matter, copulation for both males and females that had previously been exposed to imidacloprid was delayed compared with no-pesticide controls. Furthermore, for pesticide-exposed males, subsequently burrowing through media made copulation even more delayed than if they were not exposed to media. For pesticide-exposed females, subsequently burrowing through media neither increased or decreased the negative effect of the pesticide exposure. Together with other studies, these results reinforce that use of S. endius and use of imidacloprid are incompatible, even at much lower than recommended concentration, unless application is sufficiently separated in place and time.

Spalangia endius Walker is a parasitoid wasp that is commercially available as a biological control agent for filth fly pests in livestock-rearing operations. Imidacloprid is often used to control these flies. The present study examined the sublethal effect of field-realistic concentrations of imidacloprid on mating behavior, offspring sex ratios, and male preference for virgin females. After exposure to imidacloprid, S. endius females that survived were less likely to mate than control females, which will result in male-biased sex ratios because only mated females can produce daughters. Males did not avoid exposed females, but exposed females were almost always unreceptive. Males that survived exposure to imidacloprid exhibited reduced mating competitiveness against unexposed males. However, if an exposed male mated, his mate's sex ratio and ability to control flies was unaffected. Exposed males were also still able to discriminate against mated, and thus usually unreceptive, females. Together with previous studies, these results suggest that not only does imidacloprid reduce the ability of S. endius females to survive and parasitize hosts, but when an exposed female does survive and parasitize hosts, she is likely to produce just sons, because of her lack of receptivity. More-male-biased populations of S. endius will decrease their efficacy for fly control. Thus, the use of imidacloprid along with this parasitoid may be financially inefficient for pest management.

Sex pheromones play a crucial role in the mate finding process of insects. The information has to be encoded in a species specific manner to avoid fitness costs due to courtship by or even mismating with closely related species. Hence, sex pheromones normally diversify when new species evolve. Pheromones of closely related species typically vary in their chemical composition, but the compounds they use are often biosynthetically related. The biosynthetic pathways of insect pheromones are variations of conserved pathways that lead to primary and secondary metabolites. A switch from one pathway to another, particularly in species that use the same type of pheromone glands, is the exception. Here we use chemical analyses and behavioral bioassays to examine the male sex pheromone of the parasitoid wasp Urolepis rufipes. The genus Urolepis is most closely related to Nasonia and Trichomalopsis, forming the so-called "Nasonia group." All Nasonia species and T. sarcophagae, the only Trichomalopsis species studied so far, produce fatty acid-derived hydroxylactones in their rectal vesicle. The pheromones are deposited on the ground and other substrates and attract virgin females. We show that males of U. rufipes produce a sex pheromone in the same gland and use it in the same manner as the other species of the Nasonia group. Structure elucidation and stable isotope labeling experiments revealed, however, that the U. rufipes pheromone is 2,6-dimethyl-7-octene-1,6-diol, a monoterpenoid derived from the mevalonate pathway. This suggests a biosynthetic switch between the fatty acid and isoprenoid metabolism in the Nasonia group.

Use of insecticidal baits risks the evolution of resistance to the feeding stimulant in the bait, not just to the active ingredient (toxicant). Sucrose-based baits are widely used against house flies, Musca domestica L. The baits are applied as dry granules, but readily liquefy. The proboscis extension reflex (PER) and consumption of alternative sweeteners, dry or in solution, were examined. Fructose, glucose, and xylitol merit further study as alternatives to sucrose. Dry, fructose, glucose, and xylitol elicited PER much more than sucrose, although not when in solution. Furthermore, dry or in solution, females and males ate as much or more fructose as sucrose. In solution, flies ate as much glucose as sucrose; although when dry, consumption was much less for glucose than sucrose. Dry, xylitol elicited as much consumption as sucrose for females, though less for males. In solution, for both sexes, xylitol elicited less consumption than sucrose did. Acesulfame potassium, sodium cyclamate, and sucralose do not look promising as they did not often elicit PER, whether dry or in solution. Erythritol also does not look promising. Erythritol elicited PER no more than sucrose did when dry and elicited PER much less than sucrose when in solution. Flies ate much less erythritol than sucrose whether dry or in solution.

In haplodiploid species, daughter production, but not son production, is sexual, requiring paternal contributions. Females may use male signals to choose a mate with better daughter-production potential, if the choice facilitates her production of adaptive sex ratios, e.g., female-biased sex ratios in systems operating under local mate competition (LMC). In the parasitoid wasp Urolepis rufipes , females preferred pheromone markings from males that had mated once versus multiply, were young rather than old, and were uninfected rather than infected when infection was low, but not when infection was high. Mates of singly-mated males had more female-biased offspring sex ratios than those of multiply-mated males, whereas there was no difference for mates of young versus old males. Thus, female preference for singly-mated males appears to provide indirect fitness benefits. A preference for young males, was not beneficial in the laboratory, but in nature young males may have mated less.

Although mate preferences are most commonly examined in females, they are often found in both sexes. In the parasitoid wasp Urolepis rufipes, both female and male mating status affected certain aspects of sexual interactions. Female mating status mattered only in the later stages of mating. Males did not discriminate between virgin and mated females in terms of which they contacted or mounted first. However, once mounted, most virgin females were receptive to copulation, whereas very few mated females were. Whether a male’s mating status affected his own sexual response depended on the female’s ability to respond and the stage of mating. Examining male behavior toward dead females allowed elimination of the role of female behavior in how males responded. Virgin and mated males are both attracted to dead females as evidenced by their fanning their wings at such females. However, mated males were quicker than virgin males to contact and to mount in an experiment with dead females, whereas there was no such differential response in an experiment with live females. This difference is consistent with greater female sexual responsiveness to virgin males. Male mating status also affected female receptivity to copulate. Once mounted, live virgin females were less likely to become receptive to copulation by mated males than to virgin males, but only in a choice experiment, not in a no-choice experiment.

Female mating frequency varies among animal taxa. A benefit to females of remating has usually been found, but almost all tests have been with polyandrous species. A species being monandrous does not guarantee that mating only once benefits the female, instead the monandry may result from sexual conflict, where her failure to remate benefits her mate, but not her. The parasitoid wasp Spalangia endius (Hymenoptera: Pteromalidae) is highly monandrous. Females do not benefit from either immediate or delayed remating when their first mate is virgin. However, some females are likely to mate with already mated males because sex ratios are female-biased. Here, the effect of experimentally induced polyandry on female fitness was examined for females whose first mate had already mated four times, i.e., for fifth females. Fifth female S. endius produce significantly fewer daughters than first females. Production of daughters, but not sons, requires sperm in hymenopterans. Fifth females were experimentally induced to mate with a second male, by preventing such females' first mate from providing postcopulatory courtship. The proportion of female offspring produced by these polyandrous fifth females was greater than by monandrous fifth females and not significantly different than by monandrous first females. Total number of offspring did not differ among the three treatments. These results show that there are conditions under which females benefit from polyandry in this highly monandrous species and that the benefit is through effects on offspring sex ratio, not fecundity. Mating frequency varies widely among animals. In most of the more than 100 past studies of insect species in which females mate multiply, females benefit from remating. However, this same question has been addressed in few species in which females mate just once. In the tiny parasitic wasp studied here, females were tricked into remating. Females benefited from remating if their first mate had previously mated multiple times. The benefit was not producing more offspring, but rather being able to produce a greater proportion of daughters. Sons can be produced without sperm in wasps and wasp relatives. Explanations for why females do not normally remate include that they have been manipulated by their first mate and that waiting for a male means sacrificing searching for hosts.

The parasitoid wasps Spalangia endius Walker, Spalangia nigroaenea Curtis, and Spalangia nigra Latrielle (Hymenoptera: Pteromalidae) develop on filth fly pupae. Females burrow through decaying organic matter and parasitize hosts; whereas, at least in S. endius, males tend to stay above ground searching for mates. Both sexes lack obvious digging morphology such as enlarged forelegs and are not known to exhibit physical aggression. Size data were obtained from specimens from Illinois field-collected hosts for all three species and from a Florida laboratory colony for S. endius. The degree of sexual size dimorphism varied with body part and species, but the direction of bias was consistent between the field and laboratory specimens of S. endius. Females had wider abdomens in S. nigroaenea and S. nigra (not measured in S. endius). In all three species, females had longer heads than males, both in absolute size and relative to width. The latter is referred to as narrowness. Forewings were significantly narrower in females compared with in males for both S. endius and S. nigroaenea. Thorax narrowness was either greater in males (S. endius) or was not significantly different between the sexes (S. nigroaenea and S. nigra). Patterns of sexual size dimorphism seem consistent with females' need to store eggs and burrow. For all three species, there was overlap between males and females in all body parts measured. Thus, these size measurements will be unreliable to differentiate the sexes. Size ratios also overlapped.

Filth flies, including house flies, Musca domestica L., develop in animal manure. Adult house flies often are controlled with pesticides such as imidacloprid. How imidacloprid disseminates and persists after it contaminates manure was measured at a dairy farm. A week after application of imidacloprid via fly bait to cattle manure, a mean of approximately 4 ppm of imidacloprid, and as high as 15 ppm, was quantifiable up to 12 cm from the application site, but not farther. Laboratory experiments addressed the impact of 15 ppm of imidacloprid in manure on egg-to-adult development of house flies and on the biological control ability of a house fly pupal parasitoid, Spalangia endius Walker. In uncontaminated manure, 93% of eggs developed to adults, versus 7% in contaminated manure. In the parasitoid experiment, fly pupae were placed in contaminated or uncontaminated manure with or without S. endius. In the absence of S. endius, nearly 100% of flies emerged, with or without imidacloprid. In the presence of S. endius, only 11% of flies emerged from uncontaminated manure, versus 36% from contaminated manure; and parasitoids emerged from 82% of hosts in uncontaminated manure versus 53% in contaminated manure. These results suggest that realistic concentrations of imidacloprid in filth fly breeding habitat may interfere with house flies developing to the pupal stage, but also with parasitoids locating and utilizing house flies. However, after 1 wk, the effects on parasitoids will be low 12 cm beyond where bait was applied.

Pest management plans for house flies, Musca domestica L. (Diptera: Muscidae), often include insecticides. Because of resistance and environmental concerns with traditional insecticides, safe new pesticides and pesticide formulations are needed. The insecticidal potential of two sugar alcohols, xylitol and erythritol, against adult house flies was assessed. Flies consumed both xylitol and erythritol. The proportion of flies that exhibited the proboscis extension reflex, which is associated with feeding, did not differ significantly between the sugar alcohols and sucrose in an experiment with 20% solutions and older flies, but was less for the sugar alcohols in an experiment with 2M solutions and younger flies. When presented alone or mixed with sucrose, both sugar alcohols significantly decreased fly survival relative to just sucrose. There was a strong negative relationship with concentration and mean days survived for xylitol, but no significant relationship for erythritol or sucrose. Relative to sucrose alone, a temporary exposure to xylitol, but not to erythritol, decreased survival when sucrose was subsequently available. Although xylitol and erythritol can both decrease survival of house flies and would meet the criteria for organic farming, deaths were often not very immediate. However, continued investigation of a variety of sweeteners as feeding-stimulant alternatives to sucrose is still useful, to minimize the risk of house flies evolving resistance to the sugar in baits. Our analysis of already published data on house flies that had been repeatedly exposed to a sucrose-based bait is consistent with the evolution of sucrose-feeding avoidance.