A detector dog for screwworms (Diptera: Calliphoridae)

A male German wirehaired pointer, Canis familiaris L., was trained to search for and locate screwworm, Cochliomyia hominivorax (Coquerel); pupae; and animals infested with screwworms. The command, "find it" led to the detection of a screwworm-infested animal and the command "search" led to the detection of screwworm pupae. After approximately 5 mo of training, the dog could detect screwworm-infested animals. After 3 mo more of training, the dog could detect screwworm pupae. Through 7 August 1989, the dog had a success rate of 100% (265 tests) with training dummies and 94.7% (18 successes for 19 tests) with screwworm-infested animals, for an overall success rate of 99.7% (285 successes for 286 tests). Use of detector dogs at quarantine stations could result in increased efficiency, economic savings, and decreased possibility of reintroduction of screwworms into eradicated areas.     

Age determination in the adult screwworm (Diptera: Calliphoridae) by pteridine levels

Fluorescence spectrophotometry was used to assess the possible use of pteridines in the compound eyes to estimate the age of adult screwworms, Cochliomyia hominivorax (Coquerel). Factors affecting the quantities of pteridines include temperature and head size. No difference in pteridine levels was found among flies fed protein or carbohydrate. A regression model for estimating the age of female screwworms was constructed. The model uses head capsule size and relative pteridine quantities and assumes a constant body temperature of 30 degrees C. This regression formula has an r2 of 0.74. Our study extends the use of pteridine accumulation for age determination from obligate sanguinivorous Diptera to an autogenous species that feeds facultatively on nectar and wound exudates. The technique appears to provide a valid means to determine age of these flies.     

Population genetics and gene variation in screwworms (Diptera: Calliphoridae) from Brazil

Allozyme variation in New World screwworm,Cochliomyia hominivorax (Coquerel), populations from Brazil was examined. Variability was observed in 8 of 13 enzyme loci and the frequency of the most common allele was <0.95 for seven loci. Observed and expected heterozygosities were 0.159 and 0.165, respectively. Comparisons of the Brazilian populations with previously studied populations from Costa Rica resulted in Nei's genetic distances of between 0.000 and 0.006, with the greatest distance being between populations within Brazil. Comparisons with Mexican populations using only three loci resulted in genetic distances ≤0.031. Goodness-of-fit statistics for Hardy-Weinberg equilibrium and Wright'sF statistics indicated small deviations from expected equilibrium genotype frequencies and low levels of differentiation between populations within Brazil. Differentiation among screwworm populations from Brazil, Costa Rica, and Mexico was minimal.     

Influence of attractants on behavior of screwworms (Diptera: Calliphoridae) in a tropical wet forest in Costa Rica.

In a mark-release-recapture study, sheep wounds and rotted liver were used as attractants to study movements of the screwworm fly, Cochliomyia hominivorax (Coquerel), in a Costa Rican tropical wet forest in the wet season. When sites were monitored for less than 1 h, liver attracted between 3 and 12.2 times more flies of both sexes than did wounds, but proportionately fewer gravid and parous females. Only 24.6% of females marked at liver sites were recaptured; seldom (3.1%) did they visit sheep wounds. Females originally marked at sheep wounds remained at the study site longer, visited both sheep and liver sites, and greater than 50% were recaptured. Some females were observed for 16 d and one laid four clutches of eggs. Only 8% of the marked males were recaptured and none was recaptured less than 2 d later. Only a small proportion of the adult screwworms at a locality visited wounds on sentinel sheep; the majority of the adults were transient.     

The distribution of adult blow-flies (Diptera: Calliphoridae) along an altitudinal gradient in Central Spain

The distribution of Calliphoridae along an altitudinal gradient was investigated in Central Spain using carrion-baited traps. Significant differences were found between elevation and mean abundances of almost all species of blow-flies. Several species of flies could be grouped according to their altitudinal preferences so that samples at high elevations are defined by Calliphora vomitoria and Calliphora vicina while samples at low elevations are defined by two thermophilous species: Lucilia sericata and Chrysomya albiceps. The remaining species show preferences for mid-elevations where wooded areas are more characteristic along the altitudinal gradient. Calliphora vomitoria and Chrysomya albiceps are the most abundant species representing the 87.74 % of all captures. Both species are spatially segregated along the altitudinal gradient. The changing patterns of abundance are discussed in relation to differences in climate conditions along the altitudinal gradient concluding that the environmental variables that influence the seasonality of many species also play an important role to explain the spatial distribution.     

Allatotropic activity in the brain of female Phormia regina (Diptera: Calliphoridae)

In Phormia regina, the rate of juvenile hormone (JH) synthesis rises rapidly after the ingestion of an adequate protein meal. In a previous publication we have localized the neurons containing Manduca sexta allatotropin (Mas-AT)-like substances in the brain of P. regina and demonstrated the allatotropic effect of synthetic Mas-AT in sugar-fed flies in vitro. In this current study, we examined the possible role of the brain of P. regina after the fly received a protein meal. In vitro studies showed that the brain releases, at 8 h after a protein meal, a factor(s) with a strong allatotropic effect. This factor(s) stimulates the corpus allatum (CA) to produce 6.9 times more juvenile hormones (JHs) than the control CA. Time course studies showed that the release of this allatotropic factor(s) is temporally controlled. Only the brains collected from flies at 6 and 8 h after the onset of a liver meal release allatotropic factor(s). Injection of anti-Mas-AT antiserum partially suppressed the fly follicle development in vivo. Presence of anti-Mas-AT antiserum decreased the allatotropic effect of the brain released allatotropic factor(s) in vitro. In addition to a Mas-AT-like substance, it is possible that the brains of liver-fed P. regina females may synthesize other allatotropic factors that are chemically unrelated or partially related to Mas-AT, which cannot be recognized/neutralized by our anti-Mas-AT antiserum.     

Alternative to sentinel animals for collecting egg masses from wild females of the screwworm (Diptera: Calliphoridae).

Egg masses from wild populations of the screwworm, Cochliomyia hominivorax (Coquerel), were obtained by collecting females from rotted liver, holding them for 3 d until egg maturation and then placing them on heated ground beef for oviposition. Nearly 50% of the females oviposited. Fertility of egg masses was 66 and 95% at the two collection sites. Decreased fertility was associated with collections of virgin females. Average weight +/- SD of the egg masses was 13.7 +/- 1.40 mg; the number of eggs per mass averaged 343. This method of obtaining egg masses from wild screwworm females is a cost-effective, sensitive alternative to the use of sentinel animals in the field. The use of rotted liver costs less, takes less time, and takes less equipment than the traditional sentinel animal technique.     

A new meatless diet for adult screwworm (Diptera: Calliphoridae)

Screwworm flies, Cochliomyia hominivorax (Coquerel), were fed on honey and spray dried egg product; honey, molasses, and spray dried egg product; honey and spray dried meat protein; as well as on a control diet of honey and horsemeat, which is the standard diet used for screwworm adult colony in the mass-rearing facility. In general, the weight of eggs laid by females fed on the diet of spray dried egg product was significantly higher than that laid by females fed on the standard horsemeat diet. Egg production declined when spray dried meat protein replaced the egg product. Partial replacement of honey with molasses in the egg diet did not decrease egg production, compared with the control diet. The use of spray dried egg diet has advantages over the horsemeat diet, such as storage, handling, preparation, feeding, and expense. A cost analysis suggests that replacing the horsemeat with spray dried egg product, and half of the honey with molasses, would reduce the cost of the diet by more than US $100,000 annually.     

青藏高原丽蝇科昆虫物种多样性初探

本文从种数、特有物种和区系构成等角度分析了青藏高原丽蝇科昆虫的物种多样性。青藏高原已知丽蝇5亚科35属120种,占中国已知种数的44.28%,其中特有种55种,占该地区总种数的45.83%;区系构成以特有种、古北界 东洋界共同种及典型的东洋界种和古北界种为主,但澳洲界、新北界、非洲界和新热带界共同种也占一定比例。文中讨论了该地区特有种丰富的原因及地质历史环境对其的影响,分析了区系构成中各种区系成分的比例及形成原因。     

Faeces feeding by adult Phormia regina (Diptera: Calliphoridae): impact on reproduction

resh beef liver, sugar, and five different types of faeces were evaluated as supportive diets for egg development in the blowfly Phormia regina . Females on a sugar diet were unable to develop follicles beyond stage 3, whereas liver proved to be the best diet for complete egg maturation. Some faecal diets were unable to support egg maturation when fed upon for a short period of time; however, longer periods of feeding produced complete egg maturation. The necessity to feed for longer periods of time in order to produce eggs on most of these diets was attributed to their low protein content. Males, in a shorter period of time than females, obtained enough protein from faeces to activate the neuroendocrine system involved in mating.     

Laboratory environment effects on the reproduction and mortality of adult screwworm (Diptera: Calliphoridae)

The New World screwworm, Cochliomyia hominivorax Coquerel, is mass reared for screwworm eradication initiatives that use the sterile insect technique. New methods for rearing have helped to reduce the cost of the eradication program. We examined the effect and interaction of three temperatures (24.5, 29.5 and 34.5 degrees C), two diets (2% spray-dried blood plus 0.05% vitamins and corn syrup carrageenan) and three population densities (300, 400, and 500 flies/cage) on egg production, egg hatch, number of observable fertilized eggs, mortality (male and female) and ovarian development. The three population densities did not affect any of the parameters monitored. Using the protein diet increased egg production at all temperatures. Diet did not affect egg hatch or female mortality. Male mortality was significantly greater when fed the protein diet and reared at 24.5 degrees C and 34.5 degrees C. Egg hatch was significantly less when the flies were reared at 34.5 degrees C. When exposed to high temperatures (37 degrees C and 40 degrees C) egg production, egg hatch, fertility and mortality were adversely affected. At the higher temperatures, yolk did not adequately form during oogenesis. When compared to the normal rearing photoperiod (12 L:12 D), short photoperiod (1 L:23 D) increased egg production, egg hatch and fertility but lowered mortality.     

Macrolarviparous reproduction in Ameniinae (Diptera: Calliphoridae)

Female flies of the subfamily Ameniinae were found by dissection to be macrolarviparous. The two ovaries each comprise two ovarioles, and a single egg passes at a time intoa large, muscular uterus, where it hatches and develops through the soft and rather featureless first larval instar. The larva moults in utero to a strongly spined, active second instar, with long, curved mandibular hooks and this stage is presumed to parasitize snails. Details are given of the larval morphology of Amenia and Paramenia spp., and the indications that these give about taxonomic affinities. The posterior spiracles are sunk in a deep pit, as is found amongst Sarcophagidae. It is concluded that on the basis of adult and larval characters the Ameniinae is a somewhat specialized group of flies, most closely related to Calliphoridae and with some affinity to Sarcophagidae.     

A pharmacological and endocrinological study of female insemination inPhormia regina (Diptera: Calliphoridae)

Injections of octopamine, dopamine, and the octopaminergic agonists, clonidine and naphazoline, into the thoracic hemocoel enhanced female insemination in sugar-fed (sexually unreceptive)Phormia regina. Topical applications of the juvenile hormone (JH) analogue, methoprene, also enhanced female insemination in sugar-fed (sexually unreceptive)P. regina. Since JH plays a role in receptivity in protein-fed females, it was originally hypothesized that one agonist, clonidine, enhanced female insemination by acting on the corpus allatum (CA) to increase JH biosynthesis. Two or three doses of the antiallatal agent, precocene II, prior to administration of clonidine, did not inhibit clonidine-enhanced female insemination. Removal of the corpus allatum also did not have a significant effect on clonidine-enhanced female insemination. Measurement of juvenile hormone (JH) biosynthesis/release in corpora allata, which were removed at 1, 3, 5, and 7 h postinjection, revealed that clonidine does not affect JH biosynthesis/release. Our study reveals a possible role for the biogenic amines in female insemination in insects. We suggest that the octopaminergic agonist, clonidine, acts downstream from the corpus allatum on the regulatory mechanisms involved in female insemination.     

Development of female accessory glands of Chrysomya putoria (Wiedemann) (Diptera: Calliphoridae) during oogenesis

Females of Chrysomya putoria (Diptera: Calliphoridae) have two sexual accessory glands, which are tubular and more dilated at the distal extremity. The glands open independently into the common oviduct. Two morpho-physiological regions were distinguished in the longitudinal semi-thin sections of the glands. The secretory region is constituted by three layers: a cuticular intima, lining the lumen, followed by a layer of small cells, and then a layer of very large secretory cells. The ductal region of the gland presents only two layers: the cuticular intima and a cellular layer. In both regions a basement membrane is present. Each secretory cell has in its apical region a reservoir, which enlarges throughout oogenesis; in its basal region there is a large nucleus. The ductal cells are cylindrical and smaller than the secretory cells. The glandular secretion is synthesized in the cytoplasm of the secretory cells, stored and/or modified in the reservoir, then drained to the lumen through an end apparatus seen in the apical region of the secretory cell. Histochemical tests indicate that this secretion is a glycoprotein. Measurements of the glands from females at different physiological conditions and fed on different diets correlate with the results obtained for changes in the ovary during oogenesis. Cell number averaged 561.2 ± 77.54 per gland. There was no increase in cell number during oogenesis.     

丝光绿蝇触角鞭节感受器官超显微形态研究

【目的】观察研究重要的医学昆虫丝光绿蝇Lucilia sericata触角感受器的形态,以明确不同类型感受器的结构及功能。【方法】采用透射电镜与激光共聚焦显微镜技术相结合的方法。【结果】明确并详细描述了毛型感受器、锥型感受器、腔锥型感受器及感觉囊的形态结构。【结论】毛型感受器和锥型感受器可能为化学感受器,腔锥型感受器可能为温湿度感受器;感觉囊中的无孔锥型感受器可能为温湿度感受器,类锥型感受器及类腔锥型感受器可能为化学感受器,各类型感受器同时行使功能,表明感觉囊为一个功能复合体。蝇类触角的感器类型多样、囊结构复杂,可作为研究昆虫触角感器形态、功能及演化的模式类群。     

Monitoring adult populations of the screwworm (Diptera: Calliphoridae) with feeding stations baited with liver.

Populations of the screwworm, Cochliomyia hominivorax (Coquerel), were monitored by capturing adults with hand nets and rooted liver set on the ground. Adults were marked and released. During the 61-d study conducted in a tropical dry forest in the dry season (January to March 1989), 2,640 individual females and 460 individual males were recorded at the four liver-baited stations. The total number of visits by females was 5,769 and by males 510. The mean number of unmarked adults per day was 44.1 females and 7.6 males in an area of approximately 2.59 km2. The mean percentage of marked flies that were recovered was 64.3%. The mean number of feeding stations visited, times recaptured, and days in the study area by individual females was 2.1, 2.4, and 4.5, respectively. Daily visitational patterns by both sexes at the feeding stations were bimodal with peaks occurring between the hours of 0730 to 0859 and 1500 to 1629. Flies were most active when the mean temperature was 29.9 degrees C; the majority of the visits occurred when air temperatures were between 26 and 33 degrees C. Most females attracted to feeding stations were nulliparous (70.7%) and mated (69.7%). Our results suggest that observing adults at feeding stations is a reliable method of obtaining data on the behaviour and population dynamics of indigenous populations of screwworm adults in tropical habitats. Although this method was labor intensive, the amount of data gleaned from the manipulation of wild populations more than compensated for such costs.