Dipteran Pupae Research Articles

Hydroacoustic assessment of pelagic stages of freshwater insects

Two independent surveys showed that aquatic insects can generate echoes comparable with the echoes of small fish. In the open water of two fishless mountain acidic waters of the Czech Republic, a very distinct population of well-defined single targets resembling fish (target strength –66 to –50 dB at 120 kHz) was discovered. These targets were found in the depth range of 5–7 m during the day (June–July 1997). At night, most targets were recorded by horizontal beaming (depth < 3 m). Towing of ichthyoplankton nets in these horizons revealed the presence of ‘water bugs’, Corixidae (Hemiptera), mostly genus Glaenocorisa. Target strengths of corixids was also verified by direct observations in an experimental tank, where it was possible to track side, dorsal and ventral aspects. In three Dutch reservoirs, Petrusplaat, Honderd-en-Dertig and De Gijster (area 100–300 ha, maximum depth 15–28 m, with fish presence) the targets of ascending dipteran pupae (Chironomidae, Procladius signatus) with target strength of –74 to –65 dB were observed by vertical beaming. The presence of pupae was verified by horizontally towed ichthyoplankton nets and by vertical plankton hauls inside the echosounder beam. The contribution of aquatic insects to the fish biomass was small but they can interfere in juvenile fish assessment.

Dípteros muscóides associados com fezes bovinas e seus parasitóides em Goiás

A total number of 8779 pupae of Diptera were collected in stables in the municipal district of Itumbiara, GO, Brazil, from June to December 1999. The principal fly and parasitoid species found were Musca domestica L. (38.4%), Sarcophagula occidua Fabricius (51.5%) (flies), Pachycrepoideus vindemiae (Rondani) (28.0%) and Paraganaspis egeria Diaz & Gallardo (29.3%).

Infochemicals mediating the foraging behaviour of Aleochara bilineata Gyllenhal adults: sources of attractants

Abstract Aleochara bilineata Gyll. (Coleoptera: Staphylinidae) adults feed on eggs and larvae of cabbage maggot, Delia radicum (L.) (Diptera: Anthomyiidae), and might be used to control this pest. We undertook tests in a Y‐tube olfactometer to determine if infochemicals are involved in the food foraging behaviour of A. bilineata adults and to precisely determine the potential sources of stimuli. A. bilineata adults oriented toward the stimuli from both the food‐plant of the prey (rutabaga: Brassica napus var. napobrassica (L.) Reichb.) and the prey‐plant complex (rutabaga infested by cabbage maggot larvae), but adults significantly preferred the effluvia of infested to uninfested rutabaga in a choice test. The sources of infochemicals in the infested rutabaga were the cabbage maggot larvae themselves and their frass. However, in a choice test adults preferred the effluvia of the larvae to that of the damaged rutabaga from which those larvae were obtained. It is not expected that a generalist predator uses precise herbivore‐derived signals in food foraging activity, but the preference of A. bilineata adults for the larval volatiles over frass volatiles may reflect the dependence of this species on dipteran pupae for reproduction.

Intra- and interspecific host discrimination by host-seeking larvae of coleopteran parasitoids

Intraspecific host discrimination is widespread in solitary parasitoids whose adult females forage for and evaluate host suitability, whereas interspecific discrimination is less common. In some parasitoid species, mostly Diptera and Coleoptera, the larva performs the last step of host searching. It has been suggested that host discrimination will rarely occur in such host-seeking larvae because their low mobility results in a low host encounter rate. We determined the extent to which the larvae of Aleochara bilineata Gyllenhal (Coleoptera: Staphylinidae), a solitary parasitoid of aggregated Diptera pupae: (1) discriminated between unparasitized hosts and hosts parasitized by conspecifics; (2) used semiochemical cues to discriminate; (3) were influenced by life expectancy, presence of conspecifics and host availability in their host acceptance decision; and the extent to which (4) A. bilineata and A. bipustulata L., a species exploiting the same hosts and occurring sympatrically, showed interspecific host discrimination. A. bilineata larvae were able to discriminate between unparasitized hosts and hosts parasitized by conspecifics in a choice experiment. Such behavior has never previously been described for a coleopteran parasitoid or for a parasitoid species whose larvae perform host searching. Host discrimination in this species was not based on the presence of visual or tactile cues (e.g., entrance holes) but rather on chemical cues. The life expectancy of A. bilineata larvae was significantly shorter in the presence than in absence of hosts, and older larvae had lower parasitism success than young larvae in a 24-h experiment. However, the host acceptance decision of A. bilineata larvae was not influenced by larval age or the presence of conspecifics when the ratio of hosts per larva was greater than or equal to 1. When hosts were scarce, the degree of superparasitism increased significantly with the number of foraging conspecifics and the age of the larvae. Both species of Aleochara showed intra- and interspecific host discrimination in a choice experiment. In contrast to A. bipustulata, A. bilineata larvae more frequently parasitized hosts parasitized by A. bipustulata than those parasitized by conspecifics. We suggest that host discrimination will be frequent in solitary parasitoids with host-seeking larvae when hosts are aggregated.

Changes in the structure of dung insect communities after ivermectin usage in a grassland ecosystem. II. Impact of ivermectin under high-rainfall conditions

Abstract A large-scale field study was carried out to assess the ecotoxicological effect of ivermectin, a broad-spectrum veterinary agent, on dung insect communities under normal extensive farming conditions in South Africa. Dung insect communities were monitored: i) one year after a first treatment of entire herds with a single standard injection of ivermectin (200 μ·kg−1) in the 1992/93 season; and ii) for three months after a second single standard injection in the 1993/94 season. Two herds were treated with a single standard injection of ivermectin while two herds remained untreated as controls. Each herd was held in a paddock of about 80 ha. Field work was carried out in the rainy season of 1993/94, when the study area received above-average rainfall. The impact of ivermectin was examined using a variety of community measures, including univariate, graphical and multivariate methods. No effect of ivermectin on dung insect communities was observable one year after the 1992/93 treatment. Seven days after treatment in the 1993/94 season, fewer hydrophilid larvae, and scarabaeid and dipteran pupae were present in pats from treated animals in comparison with untreated controls. One and three months after treatment, there were no effects that could be attributed directly to the treatment with ivermectin. The results of the study indicate that the seriousness of the impact of ivermectin depends on several factors, including climatic conditions, spatial scale of treatment and number of animals treated in a herd.

The Origin of GregariousMuscidifurax(Hymenoptera: Pteromalidae) in North America: An Analysis Using Molecular Markers

Parasitic wasps of the genus Muscidifurax (Hymenoptera: Pteromalidae) are pupal parasitoids of various diptera and are important biological control agents of flies that breed in accumulated animal wastes and garbage. Most species of Muscidifurax, including both North American species Muscidifurax raptor and Muscidifurax zaraptor, oviposit a single egg on each host (solitary oviposition). Recent collections in the central United States, however, have revealed populations of Muscidifurax with gregarious oviposition. Previously, the only known gregarious Muscidifurax was the South American species Muscidifurax raptorellus, which is gregarious in Chile but solitary in Peru. We have developed species-specific molecular markers for the genus Muscidifurax by RAPD–PCR and have used these markers to identify the origin of gregariousness in North America. Banding patterns from three of four primers clearly distinguished M. raptor, M. zaraptor, and M. raptorellus, and those from the gregarious North American population most closely resembled those of South American M. raptorellus. We conclude that the appearance of gregarious oviposition in central North America resulted from the introduction of gregarious M. raptorellus, rather than a novel development of gregariousness within existing populations of M. raptor or M. zaraptor. Gregarious Muscidifurax are very aggressive in the laboratory and are effective biological control agents, but how they interact with other parasitoid species that attack dipteran pupae in the field remains unknown.

Distribution and feeding of juvenile Pacific salmon in freshwater tidal creeks of the lower Fraser River, British Columbia

Abstract This study examined juvenile salmonid use of a freshwater tidal creek system draining a wetland on the floodplain of the lower Fraser River, British Columbia, Canada. Chum, Oncorhynchus keta (Walbaum), chinook, O. tshawytscha (Walbaum), and sockeye, O. nerka (Walbaum), salmon fry were abundant in the tidal creeks in spring. The fry were found in non‐natal habitat up to 1.5 km from the main channel of the river. The salmon fry ate dipteran adults, larvae and pupae, cyclopoid and harpacticoid copepods, and Collembola. Mysids Neomysis mercedis Holmes (Walbaum), and amphipods, Crangonyx richmondensis occidentalis (Hubricht and Harrison), were also consumed. The upper reaches of an undisturbed creek were the winter rearing habitat for presmolt coho salmon, O. kisutch (Walbaum), where this species ate dipteran pupae and larvae as well as a freshwater isopod, Asellus communis Say (Walbaum).

Feeding Selectivity of the American Eel Anguilla rostrata (LeSueur) in the Upper Delaware River

-The population of American eels Anguilla rostrata (LeSueur) residing in the Upper Delaware River was sampled monthly from May through August 1986. Gastric examination of 325 eels captured by electrofishing revealed that 154 (47%) were empty and 171 (53%) contained food items. The specimens examined contained 2992 organisms of 59 taxa (four fish and 55 macroinvertebrate) and three non-organism categories. Macroinvertebrates, predominantly of the Class Insecta, were eaten by 169 eels (99% of feeding eels). The orders Ephemeroptera and Plecoptera occurred most often in eel stomachs (69%). The stonefly Acroneuria was the single most numerically dominant taxon observed in the diet, occurring in 67% of eel stomachs that contained food. Fishes were consumed by 12 eels (7%). The clustering near zero of electivity values for the overall study suggests that eels feed opportunistically on many macroinvertebrate taxa. The values also indicate that five food taxa were significantly (P < 0.05) selected as prey by American eels: Baetidae, Drunella, Perlidae, Hydropsyche and Polycentropodidae. The orders Ephemeroptera, Plecoptera and Trichoptera accounted for 92.7% of the organisms consumed, although they comprised 48. 1% of the available organisms. Ten food taxa were significantly (P < 0.05) avoided as prey by eels: Planaridae, Oligochaeta, Pelecypoda, Gastropoda, Gammaridae, Cheumatopsyche, Lepidostoma, Elmidae larvae, Dipteran pupae and Chironomidae. The insect orders Diptera and Coleoptera and the phylum Gastropoda accounted for 4.8% of the organisms consumed, although they comprised 32% of the available organisms.

Biotic and Abiotic Determinants of the Diet of Brook Trout, Salvelinus fontinalis, in Lakes of the Laurentian Shield

From a survey of 12 lakes containing brook trout, Salvelinus fontinalis, 12 lakes containing brook trout and creek chub, Semotilus atromaculatus, and 13 lakes containing brook trout and white sucker, Catostomus commersoni, we built seven multiple linear regression models to account for the mean percent weight of different prey categories in the diet of brook trout. Presence of chub and sucker, zooplankton community structure, sampling date, morphoedaphic index, and the importance of rock outcrops accounted for 88% of the variation in weight of zoobenthos eaten by trout, which was the preferred prey in allopatry. Thirty percent of the variation in weight of zooplankton eaten by trout was explained by the importance of macrophytes and other refuges for fish. Models for amphipods, dipteran pupae, swimming insects, terrestrial insects, and prey-fish explained between 36 and 63% of the variation. The presence of white sucker or an index of their impact (mean length or density of Cladocera) and the characteristics of littoral habitats appeared in six of seven models. Littorasl habitats seemed particularly determinant for the inclusion of prey-fish in the diet, more prey-fish being eaten when regufes were abundant. Variables related to lake morphometry and physicochemistry appeared less regularly in the models.

Host Feeding and Egg Production in Muscidifurax zaraptor (Hymenoptera: Pteromalidae)

Muscidifurax zaraptor (Hymenoptera: Pteromalidae) is a host feeding synovigenic parasitoid of the pupae of Diptera that breed in animal filth. In a laboratory experiment, we compared the numbers of eggs matured over 3 days by females under three treatments: host feeding on houseflies (Musca domestica L.), sugar feeding, and starvation. Starved females resorbed eggs. Host-fed females matured eggs at a constant rate whether they were newly emerged, had been previously starved for 3 days, or had been previously sugar-fed for 3 days. After 3 days of host feeding, females carried approximately 20 mature eggs. Sugar-fed females neither increased nor decreased the numbers of eggs they carried over 3 days, but how many eggs they carry depends greatly on previous diet. No change in the numbers of eggs under sugar feeding occurs because the rates of maturation and resorption are probably equal when hosts are not available for feeding or oviposition.

Ontogenetic changes in diel activity, food habits and spatial distribution of juvenile and adult creek chub, Semotilus atromaculatus

Juvenile creek chub, Semotilus atromaculatus, differed ecologically from adults. They were essentially diurnal, fed on small prey (adult diptera and aquatic adult coleoptera) and were found mainly in shallow littoral water (0.8 m depth) of a Quebec oligotrophic lake. In contrast, adults were principally nocturnal, fed on larger prey (Gammaridae, diptera larvae, diptera pupae and ephemeroptera larvae) and were found in deeper water (1.2, 2.0 and 2.9 m depth). The overlap in diet between juvenile and adult fish was 10 percent. We found that predation by brook charr, Salvelinus fontinalis, upon creek chub was low, as only 5 chart stomachs of the 302 examined contained a total of 16 juvenile chub and none contained adult chub. Laboratory observations revealed that under low light intensity (0.17 lux) adult creek chub fed as efficiently as under high light intensity (22 lux). Several possible hypotheses to explain the evolution of the two different strategies exhibed by adult and juvenile creek chub are discussed.

Evidence Against Competition between Trout and Nongame Fishes in Stampede Reservoir, California

Food habits of exotic brown trout (Salmo trutta) and rainbow trout (Salmo gairdnerii) and of two native nongame fishes, tni chub (Gila bicoior) and Tahoe sucker (Catostomus tahoensis) were investigated in a California subalpine reservoir. Competition for food resources between trout and native fishes is often cited as the cause for decreased salmonid angling success. The data indicated a minimal dietary overlap between the primarily limnetic-feeding trout and the benthic-feeding sucker, even when food resource levels decline in early fall. Although both trout and tui chub are limnetic feeders, they appear to partition resources sufficiently to avoid competition. Trout are highly specialized feeders on Daphnia and dipteran pupae (displaying significantly greater selectivity than nongame fishes) until reaching a piscivorous size (>300 mm). Once trout change over to a piscivorous diet, they not only display minimal food overlap with nongame fishes, but also feed heavily on small tui chubs and suckers. Although competition for food between trout and native fishes is unlikely, inter-specific competition between the morphologically and behaviorally similar brown trout and rainbow trout is likely.

The effect of diet on the ultrastructure of the mid-gut cells of Nasonia vitripennis (Walk.) (Insecta: Hymenoptera) at various ages

The ultrastructure of mid-gut cells of female Nasonia fed on a diet of 10% sterile sucrose is described. There are extensive alterations in cell organelles, particularly the mitochondria, rough endoplasmic reticulum (R.E.R.) and lipid inclusions, when compared to similar insects fed a normal diet of dipteran pupae. A proportion of the mitochondria found in the apical cell region are enlarged in size and contain electron-dense granules. The remaining mitochondria are smaller, but also contain electron-dense granules. Cytochrome-c oxidase activity appears to be absent from the enlarged mitochondria. The R.E.R. appears reduced in many cells of the 1 day old, sugar-fed insects, however, this component fluctuates throughout the remaining life span. The lipid inclusions prominent in the 1 day old, pupae-fed insects are not present in sucrose-fed females of the same age, but lipid deposition was recorded later in the life span. There are many large residual bodies and cytolysosomes present in the old, sugar-fed insects. These changes in ultrastructure are discussed in relation to diet and longevity.

Host Records of Parasitic Staphylinids of the Genus Aleochara in America (Coleoptera: Staphylinidae)

The larval stages of all species of Aleochara in which life histories have been investigated are ectoparasites on the pupae of Diptera within the puparium. The adults are active predators of dipteran eggs and larvae, often destroying enormous numbers. This fact has been demonstrated conclusively with Aleochara bilineata , a parasite of the cabbage maggot, Hylemya brassicae (Wadsaworth 1915, Colhoun 1953). Other species of Aleochara have not been so extensively investigated, but some host records are known. A table of these is given in which new host records are reported.

GIANT POLYTENE CHROMOSOMES IN HYPODERMAL CELLS OF DEVELOPING FOOTPADS OF DIPTERAN PUPAE.

Large hypodermal cells with giant polytene chromosomes are present within the developing feet of Sarcophaga and other fly pupae. The cells secrete a large volume of cuticle; at this time there is extensive "puffing" of the chromosomes. Being hypodermal and superficially situated with permanent secretory products, the cells could be ideal experimental and genetical tools.

A Morphological Study of the Respiratory Horns Associated with the Puparia of Some Diptera, Especially Ophyra Anescens (Wied.)1

This study concerns the respiratory horns of three species of Diptera. “Respiratory horns” is the common name given to a pair of pronglike structures which occur on the dorsolateral aspect of the cephalic half of a number of pupae and puparia of Diptera, especially among Cyclorrhapha. De Meijere (1902) made the first systematic attempt to describe the structure of the respiratory horns in various families of Diptera, drawing information both from his own observation and from the scattered descriptions in the literature. Many interesting examples of respiratory horns in pupae have been described and figured in several papers dealing with the morphology of larvae and pupae of Diptera. The figures in these papers give a clear idea of the great variations in size, shape and structure of these horns, often described as prothoracic horns, trumpets, spiracles, siphons or gills. Their size varies from short, sessile and hardly perceptible to long and distinctly prominent projections in some pupae.

Respiratory systems and respiratory adaptations in larvae and pupae of Diptera

Each year the study of Diptera reveals some new and often unexpected facts concerning the mode of life of their early stages. The rich entomological literature dealing with this subject clearly shows that the diversity of conditions under which the larvae of this order of insects live surpasses that of any other order of the Animal Kingdom.