Predatory Flies Research Articles

Separation of three common hover fly predators of woolly apple aphid based on the exochorionic sculpturing of eggs

The woolly apple aphid, Eriosoma lanigerum (Hausmann, 1802) (Hemiptera: Aphididae), is a cosmopolitan, indirect pest of cultivated apple, Malus domestica (Borkh.) (Rosaceae), (Baker 1915) that can colonize both the roots and arboreal portions of trees and adversely affect the growth, vigor, and productivity of the host (Weber and Brown 1988; Brown and Schmitt 1990; Brown et al. 1991, 1995). Historically, the solitary endoparasitoid Aphelinus mali (Haldeman, 1851) (Hymenoptera: Aphelinidae) has been considered the most important biological control agent for E. lanigerum in many, but not all, apple-growing regions (Yothers 1953; Nicholas 2000). The role of arthropod predators in regulating woolly apple aphid populations, particularly early in the growing season, has long been recognized (Dumbleton and Jeffreys 1938; Bodenheimer 1947; Nicholas 2000; Mols and Boers 2001) but has not been adequately addressed (Asante 1997).

Feeding by black fly (Diptera:Simuliidae) larvae causes downstream losses in phytoplankton, but not bacteria

Experimental removal of early instar black fly larvae from 3 oligotrophic lake-outlet streams in southern Quebec showed that larvae reduced phytoplankton biomass, but had little effect on bacterioplankton biomass. The rates of decline in bacterioplankton and phytoplankton biomass with distance downstream from 6 lake outlets were determined before the insecticide Bacillus thuringiensis var. israelensis was used to remove black fly larvae from 3 of the streams. The rates of decline in bacterioplankton and phytoplankton biomass were measured again after the larvae were removed, and the differences in the rates of decline between before and after were used as indicators of the rates of biomass ingestion by the black fly larvae. The proportion of bacterioplankton ingested/m stream length was <0.081%/m in all streams, but the proportion of phytoplankton ingested/m stream length was 0.35%/m and 0.24%/m in 2 of the 3 manipulated streams. Downstream declines in both bacterioplankton and phytoplankton persisted in the absence of black fly larvae. Factors other than black fly feeding (such as biofilm adhesion and ingestion by other filter-feeders) were responsible for 50 to 90% of the total downstream loss rate of bacteria, whereas factors other than black fly feeding were responsible for 0 to 55% of the total downstream loss rate of phytoplankton. Apparently, free-living bacteria were not ingested to a great extent by black fly larvae in these oligotrophic lake-outlet streams, and the link between bacteria in the plankton and their potential black fly predators seemed weak. The relative importance of algivory over bacterivory is expected to be greater in eutrophic lake-outlet streams, where the ratio of bacterial C to phytoplankton C is smaller than in oligotrophic lake-outlet streams, and in systems with a greater abundance of later-instar larvae, which are less efficient at capturing bacteria than early instar larvae.

Feeding and Egg Distribution Studies of &lt;I&gt;Heringia calcarata&lt;/I&gt; (Diptera: Syrphidae), a Specialized Predator of Woolly Apple Aphid (Homoptera: Eriosomatidae) in Virginia Apple Orchards

Predation by the aphidophagous syrphid fly Heringia calcarata (Loew) on woolly apple aphid, Eriosoma lanigerum (Hausmann), was studied in the laboratory and in Virginia apple orchards. Feeding studies compared the prey suitability of three temporally sympatric aphid pests of apple: spirea aphid, Aphis spiraecola Patch; rosy apple aphid, Dysaphis plantaginea (Passerini); and woolly apple aphid. Significantly more H. calcarata larvae survived and completed development on a pure diet of woolly apple aphid than on rosy apple aphid, and none survived on spirea aphid. Final larval weights were significantly greater, and the larval developmental period was significantly shorter on woolly apple aphid than on rosy apple aphid, but neither the duration of pupal development nor adult weight differed between diets. H. calcarata larvae consumed an average of 105 woolly apple aphids during their development. Naïve, neonate larvae given access to all possible pair combinations of woolly apple aphid, rosy apple aphid, and spirea aphid consumed significantly more woolly apple aphids in all pairings that included woolly apple aphid. When given a choice of rosy apple aphid and spirea aphid, significantly more rosy apple aphids were consumed. Weekly counts of syrphid eggs found in woolly apple aphid, rosy apple aphid, and spirea aphid colonies collected from apple trees showed that two generalist hover fly predators, Eupeodes americanus (Wiedemann) and Syrphus rectus Osten Sacken, were present in colonies of all three aphid species and that E. americanus was the most abundant syrphid predator in A. spiraecola and D. plantaginea colonies. H. calcarata eggs were found only in woolly apple aphid colonies and were more abundant there than E. americanus and S. rectus. These data suggest that H. calcarata is a specialized predator of woolly apple aphid in the apple ecosystem in Virginia.

Feeding and egg distribution studies of Heringia calcarata (Diptera: Syrphidae), a specialized predator of woolly apple aphid (Homoptera: Eriosomatidae) in Virginia apple orchards.

Predation by the aphidophagous syrphid fly Heringia calcarata (Loew) on woolly apple aphid, Eriosoma lanigerum (Hausmann), was studied in the laboratory and in Virginia apple orchards. Feeding studies compared the prey suitability of three temporally sympatric aphid pests of apple: spirea aphid, Aphis spiraecola Patch; rosy apple aphid, Dysaphis plantaginea (Passerini); and woolly apple aphid. Significantly more H. calcarata larvae survived and completed development on a pure diet of woolly apple aphid than on rosy apple aphid, and none survived on spirea aphid. Final larval weights were significantly greater, and the larval developmental period was significantly shorter on woolly apple aphid than on rosy apple aphid, but neither the duration of pupal development nor adult weight differed between diets. H. calcarata larvae consumed an average of 105 woolly apple aphids during their development. Naïve, neonate larvae given access to all possible pair combinations of woolly apple aphid, rosy apple aphid, and spirea aphid consumed significantly more woolly apple aphids in all pairings that included woolly apple aphid. When given a choice of rosy apple aphid and spirea aphid, significantly more rosy apple aphids were consumed. Weekly counts of syrphid eggs found in woolly apple aphid, rosy apple aphid, and spirea aphid colonies collected from apple trees showed that two generalist hover fly predators, Eupeodes americanus (Wiedemann) and Syrphus rectus Osten Sacken, were present in colonies of all three aphid species and that E. americanus was the most abundant syrphid predator in A. spiraecola and D. plantaginea colonies. H. calcarata eggs were found only in woolly apple aphid colonies and were more abundant there than E. americanus and S. rectus. These data suggest that H. calcarata is a specialized predator of woolly apple aphid in the apple ecosystem in Virginia.

Effects of decomposition on carcass attendance in a guild of carrion-breeding flies.

Many forensically important calliphorids, sarcophagids and muscids (Diptera) oviposit or larviposit on corpses only during the early stages of decomposition, yet individuals may attend bodies throughout decay. A field study was conducted to investigate how patterns of carcass use and attendance by some fly species are affected by decomposition. Five fly traps were placed in the forest and baited with whole, fresh piglet carcasses. Piglets decomposed in traps throughout the experiment, and all were skeletonized within 6 days. Flies were trapped at both early and late decomposition stages, and the species and population structures of trap catches were compared. More flies attended carcasses early rather than late in decay. For all species, flies attending early were mainly gravid females, but few gravid females attended late in decay. No females ovi- or larviposited late in decay, whereas females of all fly species deposited offspring early in decay. The number of males trapped of each species correlated positively with the number of females with eggs at early development stages. Observations were made of fly predation by European wasps Vespula germanica Fabricius (Hymenoptera, Vespidae) and jumper ants Myrmecia pilosula Smith (Hymenoptera, Formicidae) throughout the experiment. There was a higher risk for smaller fly species of being killed following predator attack. Ants and wasps attacked smaller fly species, whereas only wasps attacked larger fly species.

The spider and fly revisited: ploy-counterploy behavior in a unique predator-prey system

Earlier studies have shown that the sarcophagid fly Arachnidomyia lindae is the principal egg-sac predator of the colonial orb-weaving spider Metepeira incrassata, and that risk of egg-sac loss increases with group size. Observations of specialized behaviors for attack (flies) and defense (spiders) suggest that this predator–prey relationship may incorporate elements of ploy and counterploy behavior. Here we explore this relationship in detail and test hypotheses regarding efficacy of attack and defense behaviors. Egg-sac guarding by the spider includes defensive behaviors specific to this fly predator, which were observed during experimental "attacks" with tethered A. lindae, but not with similar presentations of non-predatory Musca domestica. Experimental studies also show that Metepeira incrassata recognizes this predatory fly by airborne cues (i.e., the signature frequency of wing-beats), and can distinguish between this predator and other flies (potential prey) on the basis of wing-beat frequency differences. Removal of female spiders results in a significantly higher probability of unguarded egg-sacs being parasitized, demonstrating the adaptive value of spider defensive behaviors. We also present evidence that A. lindae utilizes a behavioral ploy for circumventing spider guarding behavior (aggressive mimicry – producing vibrations of captured prey in the web), and that Metepeira incrassata, in turn, exhibits a counter-ploy behavior (signal thread cutting) to eliminate this potentially distracting vibratory information. While previous studies have shown that this colonial web-building spider uses a number of general attack-abatement mechanisms against a diversity of predators and parasitoids, results of this study suggest that selection pressures from a highly specialized predator may also result in evolution of predator-specific prey responses.

A review of prey choice in bembicine sand wasps (Hymenoptera: Sphecidae)

The prey of 132 species of Bembicini (Hymenoptera) that have been studied is reviewed. About three quarters of the species prey on Diptera, and it is believed that fly predation is ancestral in the group. Eleven species make occasional or regular use of other insects as prey in addition to Diptera (Lepidoptera, Hymenoptera, Neuroptera, Odonata, and/or Homoptera), while 21 species of five genera prey on insects of these same five groups with no use of Diptera. It is hypothesized that this represents an evolutionary progression, whereby populations have experienced shortages of dipterous prey in the past and have broadened their sensory focusing to include other groups of flying insects. Behavior initially learned has, over time, been reinforced genetically to produce the currently observed radiation in prey choice within the group.

Reproductive trade-offs and bet-hedging in Hyla calypsa, a Neotropical treefrog.

I studied spatial and temporal variation in reproductive activity of Hyla calypsa along a montane stream in south-central Costa Rica between 1991 and 1996. Maggots of drosophilid flies killed the greatest number of frog eggs, while mortality from other sources was random and unpredictable. Late-season increases in fly predation may select for high, early reproductive effort by the frogs. Female frogs in this population show intra-clutch and seasonal variation in egg diameter and seasonal variation in clutch size. There were no correlations between female size and egg or clutch parameters. Egg diameter varied more within a clutch than among clutches, suggesting that individual females were allowing for unpredictable environmental conditions or that the larval environment may be selecting for variation in propagule size. This species uses both bet-hedging and trade-offs between offspring size and number to maximize the chance of producing tadpoles. Future studies should determine the advantages of small and large hatchlings and whether these relate to environmental variation in the stream.

Deer Mouse Predation on the Biological Control Agent, Urophora spp., Introduced to Control Spotted Knapweed

Field observations made in 1993 suggested that rodents were preying on spotted knapweed (Centaurea maculosa) seedheads, possibly targeting the gall fly larvae (Urophora SPP.) which overwinter within them. I conducted a brief study to determine the cause of seedhead predation and quantify gall fly predation. Stomachs were examined from 19 deer mice (Pero- myscus maniculatus) captured in the fall of 1993 and winter of 1997. All individuals had preyed upon gall fly larvae. The mean number of gall fly larvae found in 10 deer mouse stomachs in the winter of 1997 was 212.8. The minimum number of larvae consumed by these 10 animals for 1 night of foraging was 2686. Availability of a concentrated protein that is a readily accessible and abundant resource during winter may elevate deer mouse populations in knapweed-in- fested habitats. Increases in densities of deer mice due to gall fly presence could bring about shifts in composition of small mammal communities.

Nationwide survey of pests and diseases of cereal and grass seed crops in New Zealand. 1. Arthropods and molluscs.

A national survey of four cereal and two grass seed crops was conducted by the New Zealand Plant Protection Centre (NZPPC) from October 1995 to February 1996. Approximately 85,000 plants were inspected at 332 sites in the main cereal growing areas of New Zealand. In addition to the previously known invertebrate species associated with cereal and grass seed crops, 93 new organism-host associations were recorded for wheat (21 primary pests), 85 new associations for barley (22 primary pests), 40 new associations for oats (8 primary pests), 25 new associations for ryecorn (3 primary pests), 57 new associations for ryegrass (15 primary pests) and 29 new associations for brome grass (5 primary pests). Cereal thrips (Limothrips cerealium), wheat sheath miner (Cerodontha australis) and Argentine stem weevil (Listronotus bonariensis) were the most common pests found in this survey. Chamaemyia polystigma, a predatory fly new to New Zealand, was recorded on barley, brome grass and ryegrass. One undescribed species of Thysanoptera was found on wheat from Mid Canterbury.

Defensive larval secretions of leaf beetles attract a specialist predator Parasyrphus nigritarsis

1. Noxious larval secretions of leaf beetles, which repel generalist predators, do not deter specialist syrphid fly predators (genus Parasyrphus). These flies cause considerable mortality to the beetles, but little is known about their foraging behaviour.2. Larvae of Parasyrphus nigritarsis were attracted to the volatile larval secretions produced by two prey species Phratora vitellinae and Linaeidea aenea. Parasyrphus nigritarsis feeds on both beetles in nature. Phratora vitellinae feeds on willows and utilizes host plant compounds for secretion production, while the alder‐feeding L. aenea produces an autogenous secretion.3. Fly larvae were strongly attracted to pieces of filter paper treated with larval secretion of the beetles. They attempted to feed on them for up to 7 min, and were equally attracted to the secretions of Ph. vitellinae and L. aenea. Fly larvae were also attracted to pure salicyl aldehyde, the main component of the secretion of Ph. vitellinae.4. Fly larvae searched extensively for prey on leaves that had been damaged by beetle larvae. They also followed trails made with solutions containing faecal matter of prey larvae. They showed no differential preference for Ph. vitellinae or L. aenea, but always rejected larvae of the non‐prey leaf beetle Agelastica alni.5. Beetle secretions thus play an important, but unexpected, role in the feeding behaviour of P. nigritarsis. This predator uses the beetle secretion to locate its prey. The implications of these results for three trophic level interactions are discussed.

Coprophilous Arthropod Community from Argentina with Species of Potential Use as Biocontrol Agents Against Pest Flies

Dung-inhabiting pest flies are one of the main problems associated with the accumulation of cattle dung. This work analyzes the diversity and dynamics of a coprophilous community from northern Buenos Aires, Argentina, in a search for potential biocontrol agents. Thirty-six dung pads of 3 age categories and 4 microhabitats were collected on each sampling date and examined for their arthropod fauna. Some of the species with undefined feeding behavior were subjected to feeding trials in the laboratory. We found 34 coprophagous species, 47 predators, and 13 parasitoids. The combination of the results of the feeding trials, co-occurrence and abundance data of the prey and predator populations, and direct field observations were used to put together a trophic web and hypothesis on the dynamics of the community. Dung scarabs cause significant reductions in immature dung fly survival by burying and desiccating large amounts of dung. The Philonthini (Coleoptera: Staphylinidae) are the most abundant and rich predator group, although they are slow to respond to variations in fly populations. However, predatory flies show the same abundance curves as their prey flies. Predatory beetles and flies, dung scarabs, and pupal parasitoids cause additive mortality to the fly population, whereas larval parasitoids cause some compensatory mortality. Four species of staphylinids, 1 predatory muscid, and a coprophagous scarab could have potential as biocontrol agents. The perspectives of success and convenience of a horn fly biocontrol scheme in southern South America are discussed.

CHANGES IN FEEDING HABITS OF SELECTED NONTARGET AQUATIC INSECTS IN RESPONSE TO LIVE AND BACILLUS THURINGIENSIS VAR. ISRAELENSIS DE BARJAC-KILLED BLACK FLY LARVAE (DIPTERA: SIMULIIDAE)

AbstractThe effects of Bacillus thuringiensis var. israelensis de Barjac (B.t.i.) on the feeding habits of two black fly predators, Nigronia serricornis (Say) and Acroneuria lycorias (Newman), and a detritivore, Prostoia completa (Walker), were examined. We assessed whether B.t.i.-killed and hot water-killed black fly larvae were less or more desirable to these consumers than live larvae. Nigronia larvae showed no significant differences in predation on larvae within the three categories. Acroneuria nymphs consumed more live than dead prey. Experiments with the detritivore, Prostoia, showed that they preferred dead black fly larvae to live ones. Bacillus thuringiensis var. israelensis treatment may have little direct effect on nontarget organisms, but these studies indicate that there still may be consequences for predators and detritivores when a viable population of larval black flies is transformed into dead organic matter.

Predator deterrence by mandibular gland secretions of bees (Hymenoptera: Apoidea)

Volatile lipids from the mandibular gland secretions of bees (Hymenoptera: Apoidea) are potent olfactory repellents of foraging ants (Formica, Crematogaster) in biologically relevant contexts and quantities. In contrast, differential success in capture of bee and fly prey by predatory asilid flies (Efferia), reduviid bugs (Apiomerus), and arachnids (Agelenopsis, Argiope) is better explained by prey size than by chemical repellence, aposematism, or possession of a sting. Supernormal doses of some allomones, applied to worker honeybees (Apis mellifera) that were fed toArgiope aurantia spiders, elicted more frequent preenvenomation pauses following ensnarement but did not significantly increase other prey-handling times. These pauses merely delayed the bee's demise. Mandibular gland secretions of solitary bees augment their other secondary defenses in at least two contexts: (1) during intranest encounters when repelling intruding ants, and (2) retaliation delivered to their arthropodan predators which, if the bee is nearly too large for the predator to handle, may allow the bee to escape.

Parasitism and Survival among Rangeland Grasshoppers in Response to Suppression of Robber Fly (Diptera: Asilidae) Predators

Robber flies were manually removed from 0.28- or 0.55-ha circular field plots four or five times a week for 6 weeks in order to reduce predation upon dipterous parasites of grasshoppers. Three species that prey upon Diptera, Efferia bicaudata (Hine), E. staminea (Williston), and Mallophorina guildiana (Williston), constituted 94% of the robber fly population. Although removal plots always become partially (mean, 61%)repopulated through recruitment or immigration, the incidence of parasitism among grasshoppers significantly increased from an average of 2 to 3% in untreated plots to 5.5 to 6.5% in removal plots. During one season, the enhancement of parasitism was associated with a significant 12-day reduction in average longevity of grasshoppers (i.e., from 40 days to only 28 days). During a second season, however, average grasshopper longevity in all plots was only 15 days, and the potential effects of increased parasitism were not realized.

Ecologically seIective coIoured traps

Abstract. 1. This paper analyses catches of flower thrips, grass thrips and predatory flies in water‐traps of seven colours.2. A correlation is demonstrated between type of host‐plant of thrips and the relative numbers caught by traps of different colours.3. The literature is reviewed and some general relationships with the effectiveness of different trap colours are hypothesized for: non‐grass foliage insects and their predators and parasites; grass foliage insects; flower‐dwelling insects; predators and parasites not associated with foliage; biting insects; and wood‐borers.4. This may permit trap colours to be chosen, in particular circumstances, that are ecologically selective for different types of insect.

Predation by Four Species of Histeridae (Coleoptera) on Horn Fly (Diptera: Muscidae)1

Four species of Histeridae, Hister coenosus Erichson, H. incertus Marseul, Xerosaprinus orbiculatus (Marseul), and Saprinus pennsylvanicus (Paykull), were studied in the laboratory to evaluate their potential as control agents of immature stages of the horn fly, Haematobia irritans (L.). When eggs, first- to third-stage larvae and newly formed pupae of the horn fly were exposed to varying numbers (one to five) of adult histerid beetles, control varied with each beetle species. Both Hister species were effective predators throughout the horn fly developmental period from egg to pupa; however, H. incertus was significantly less efficient during horn fly larval-to-pupal developmental periods. Saprinus pennsylvanicus and X. orbiculatus were significantly less effective against all horn fly immature stages than either of the Hister species. With the exception of H. coenosus , increased densities resulted in significantly greater horn fly predation.

Influence of Predators on the Efficiency of the Blaesoxipha1 spp. Parasites of the Migratory Grasshopper 2

The average longevity of adult females of three species of Blaesoxipha grasshopper parasites was estimated at 3.0 to 4.8 days under field conditions. CircumstantIal evidence suggested predation as a major cause of mortality. When parasites and grasshoppers were isolated in large cages, average survival of parasites increased about fourfold and the level of parasitism among grasshoppers increased about fivefold over field levels. In identical cage tests that included robber fly predators, all parasites were destroyed, parasitism essentially was eliminated, and the survival rate of grasshoppers increased.

Observations on the nesting behaviour of seven species ofCrabro(Hymenoptera, Sphecidae)

Summary Data are presented on the nests and prey of seven species of Crabro from diverse localities in North America. In two instances (virgatus and largior) this is the first published report. Further information is provided for the following previously studied species: argusinus, advena, cribrellifer, latipes, and monticola. Behavioural differences among these species are not conspicuous. Most are rather general fly predators, but cribrellifer appears to show a strong preference for Asilidae. There are also differences in type of soil used for nesting and in antipredator behaviour such as approach flights and daily cycles of activity. Two species, largior and monticola, provision their nests early in the morning, before miltogrammine flies are active in numbers. All species probably make cells of two sizes, larger cells containing more prey and producing females, smaller cells males.

The predators of wheat‐bulb fly

SUMMARYWheat bulb fly, a pest of winter weat, has one generation a year and all stages exist for at least a month. The feeding larva inside the shoot is protected, except when moving to a new shoot, but all the other stages are exposed to attack by non‐specific predators, either by soil‐living beetles feeding on eggs and puparia in the soil, or predatory flies and birds feeding on the adults.