DNA barcoding cannot reliably identify species of the blowfly genus Protocalliphora (Diptera: Calliphoridae)

In DNA barcoding, a short standardized DNA sequence is used to assign unknown individuals to species and aid in the discovery of new species. A fragment of the mitochondrial gene cytochrome c oxidase subunit 1 is emerging as the standard barcode region for animals. However, patterns of mitochondrial variability can be confounded by the spread of maternally transmitted bacteria that cosegregate with mitochondria. Here, we investigated the performance of barcoding in a sample comprising 12 species of the blow fly genus Protocalliphora, known to be infected with the endosymbiotic bacteria Wolbachia. We found that the barcoding approach showed very limited success: assignment of unknown individuals to species is impossible for 60% of the species, while using the technique to identify new species would underestimate the species number in the genus by 75%. This very low success of the barcoding approach is due to the non-monophyly of many of the species at the mitochondrial level. We even observed individuals from four different species with identical barcodes, which is, to our knowledge, the most extensive case of mtDNA haplotype sharing yet described. The pattern of Wolbachia infection strongly suggests that the lack of within-species monophyly results from introgressive hybridization associated with Wolbachia infection. Given that Wolbachia is known to infect between 15 and 75% of insect species, we conclude that identification at the species level based on mitochondrial sequence might not be possible for many insects. However, given that Wolbachia-associated mtDNA introgression is probably limited to very closely related species, identification at the genus level should remain possible.     

Waning of repetitive hopping in the blowfly Phormia regina Meigen (Diptera: Calliphoridae)

Wingless blowflies (Phormia reginaMeigen)released on a flat uniform substrate hop repeatedly. The rate of hopping decreases with time. Decremental responsiveness resembles behavioral habituation. It can be reestablished by tactile stimulation and is due neither to muscle fatigue nor to sensory receptor adaptation. No effects of age or circadian rhythms were observed. The initial rate of hopping increases with increasing food deprivation, as does the time for waning to be completed. Decapitated flies and isolated wingless thoraxes hop almost as well as control flies and wane at the same rates.     

Characterization of polymorphic microsatellite markers for the blowfly Chrysomya albiceps (Diptera: Calliphoridae)

Chrysomya albiceps is a blowfly of great medical, sanitary and forensic importance widely distributed in the Afrotropical, southern Palaearctic, northern Oriental regions and, recently, in Central and South Americas. Here, we report the characterization of 13 polymorphic microsatellite markers for C. albiceps. The number of alleles ranged from three to 13 alleles with expected heterozygosities ranging from 0.4668 to 0.8408. These markers will be extremely useful for investigating many important aspects of this species such as population structure, dispersal and colonization dynamics.     

Cold resistance in all life stages of two blowfly species (Diptera, Calliphoridae)

1. Freezing was lethal in the eggs, larvae, pupae and adults of the blowflies Calliphora vicina R-D. and Calliphora vomitoria (L.), but varying degrees of supercooling were found. 2. Cold resistance (as determined by their supercooling capacity) was greatest in eggs (to c. -25 degrees C), and moderate in other life stages (range -7 to -13 degrees C), which was evident from the distributions of their supercooling points. 3. Water contents of all life stages varied from 63% to 77% of fresh weight; pupae of C. vomitoria contain the smallest proportion of water. No relationship between the amount of body water and supercooling ability was detected. 4. Glucose was the major compound in all life stages of C. vicina, with a maximum concentration of 8.22 micrograms mg-1 fresh weight in the adults. In addition, five other potential cryoprotectants occurred in concentrations greater than 0.1% of fresh weight. No correlation between solute concentration and supercooling was observed. 5. Both C. vicina and C. vomitoria have sufficient cold hardiness to avoid lethal freezing in sheltered habitats in southern Britain, which may render diapause unnecessary in both species.     

Sexual size dimorphism decreases with temperature in a blowfly,Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae)

1. There is wide intra‐specific variation in sexual size dimorphism (SSD). Much of this variation is probably as a result of sexual differences in the selective pressure on body size. However, environmental variables could affect males and females differently, causing variation in SSD. 2. We examined the effects of two temperatures (20 and 30 °C) on SSD in six populations of the blowfly, Chrysomya megacephala. 3. We found that body size increased with temperature in all the populations studied, and the sexes differed in phenotypic plasticity of body size in response to rearing temperature. This created substantial temperature‐induced variation in SSD (i.e. sex × temperature interaction). Males were often smaller than females, but the degree of dimorphism was smaller at the higher temperature (30 °C) and larger at the lower temperature (20 °C). This change in SSD was not because of a gender difference in the effect of temperature on development time. Further studies should address whether this variation can be produced by adaptive canalisation of one sex against variation in temperature, or whether it may be a consequence of non‐adaptive developmental differences between the sexes. 4. Although most studies assume that the magnitude of SSD is fixed within a species, the present study demonstrates that rearing temperature can generate considerable intra‐specific variation in the degree of SSD.     

窄颊粉蝇Pollenia angustigena Wainwright——广州口岸截获的一种丽蝇

本文报道从经广州新风口岸入境加拿大木材中截获的一种丽蝇:窄颊粉蝇Pollenia angustigerta Wainwright.     

Suppression of populations of Australian sheep blowfly, Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae), with a novel blowfly trap

The Australian sheep blowfly, Lucilia cuprina , initiates more than 85% of fly strikes on sheep in Australia with an estimated average annual cost of A$280 million to the Australian sheep industry. LuciTrap^® is a commercially available, selective trap for L. cuprina consisting of a plastic bucket with multiple fly entry cones and a synthetic attractant. The impact of LuciTrap on populations of L. cuprina on sheep properties in five Australian states was evaluated by comparing L. cuprina populations on paired properties with and without LuciTraps over seasons when significant fly populations could be expected. Twenty-four comparisons (trials) were conducted over 4 years. During times of 'higher fly density' (when the 48 h geometric mean of trap catches on the control property was greater than five L. cuprina ), the overall geometric mean trap catches for control and trapped properties differed significantly ( P  < 0.001) with mean trap catches of 19.4 and 7.74 L. cuprina , respectively. The selectivity of the LuciTrap was confirmed with 59% of all trapped flies being L. cuprina . Chrysomya spp. and Calliphora spp. constituted 9.3% and 1.1% of the catches with a variety of other flies (mainly Sarcophagidae and Muscidae ) providing the remainder (31%). Lucilia sericata was only trapped in Tasmania and made up 7.7% of the Lucilia spp. catch in that state. Seventy-two per cent of the trapped L. cuprina were female. The deployment of LuciTrap on sheep properties at one trap per 100 sheep from the beginning of the anticipated fly season suppressed the populations of L. cuprina by 60% compared with matched control properties. The LuciTrap is a selective and easy to use fly trap and constitutes an effective, non-insecticidal tool for use in integrated management programs for L. cuprina .     

A simple larval diet for population studies on the blowfly Lucilia sericata (Diptera: Calliphoridae)

1. A simple artificial diet was devised for larvae of Lucilia sericata Meigen. 2. A basic diet of 20 g/l agar with 20% horse blood and added yeast sustained normal growth and development, as compared with a lamb meat control. 3. When yeast was added to the blood agar diet at 50 g/l, both peak and final larval weights were increased by 25-50% at higher larval densities (2-8 larvae/g diet) and the hatchling-adult development period was reduced by about 3 days. 4. No adult insects emerged on an agar-yeast diet without blood. Increasing the concentration of blood from 10% to 20% increased adult weight at emergence by 50%, though developmental period was not significantly affected. 5. Increasing larval density significantly reduced the weights of pupae and emergent adults (by up to 50%), both on the blood-agar-yeast diet and the lamb meat control. Percentage survival fell from 80-90% to below 10% on the blood-agar-yeast diet at the highest densities of 4 or 8 larvae/g diet, though survival on lamb was not significantly affected by density.     

Winter survival of larvae and pupae of the blowfly, Lucilia sericata (Diptera: Calliphoridae)

The mortality of larvae and pupae of the blowfly Lucilia sericata (Meigen) were examined during winter and spring, for two or three years. In soil cores in the field, 70-95% of the larvae died overwinter. Larvae congregated in the top 10 cm of the soil core and did not move extensively throughout the column during the winter. Larvae and pupae at greater depth were less likely to pupariate and emerge successfully than larvae closer to the surface. Under semi-natural conditions, where pupae were placed outside in sawdust filled tubes, in the absence of the usual biotic mortality factors, the mortality of larvae was considerably lower and was also unaffected by low winter temperatures. Hence, low temperatures did not appear to be the primary cause of high overwintering mortality in the field which, it is suggested, is more likely to be the result of the action of biotic mortality factors, such as entomopathogenic nematodes and fungi.     

Polytene chromosomes and linkage group-chromosome correlations in the Australian sheep blowfly Lucilia cuprina (Diptera: Calliphoridae)

The trichogen cell polytene chromosome maps for the Australian sheep blowfly Lucilia cuprina dorsalis R.-D. are presented. Correlations between the autosomal linkage groups and the polytene and mitotic chromosomes were accomplished using autosome-autosome and sex chromosome-autosome translocations. It is suggested that the sex chromosomes are largely inert.This work was completed during the tenure of a Fulbright fellowship and was supported in part by Public Health Service grant 2T1 GM 373-08.     

The adhesive organ of the blowfly, Calliphora vomitoria: a functional approach (Diptera: Calliphoridae)

The external morphology of the terminal region of the fifth tarsal segment of the blowfly, Calliphora vomitoria (L.) has been studied using light and scanning electron microscopy (S.E.M.). The pulvilli, with their numerous tenent hairs of spatulate form projecting from the ventral surface, are responsible for adhesion to smooth surfaces. The two large claws are believed to be important in clinging to irregularities in surfaces. Two footplates, possibly sensory organs, lie in close association with the base of the large ventral seta, the empodium. Blowflies release a non-volatile lipid secretion on to the spatulate ends of the tenent hairs and this secretion is essential to the adhesion process on smooth surfaces. The force of adhesion has been measured for tethered blowflies on glass using both vertical and lateral pulls; lateral pulls gave much greater forces. It is concluded that surface tension of the lipid secretion under tenent hairs is sufficient to enable successful adhesion to smooth surfaces by blowflies.     

Measurement of age and population age structure in the blowfly,Lucilia sericata (Meigen) (Diptera: Calliphoridae)

For field samples of the blowfly Lucilia sericata (Meigen), the degree of wing abrasion, corrected for individual size, was shown to give a useful estimate of age, by calibration against a known measure of chronological age, the fluorescence of pteridines in the head capsule. In more extensive field studies, therefore, wing fray was used to indicate the likely ovarian cycle of each female, after which the length of the most advanced egg follicle was used to give a more precise estimate of age within this cycle. Using these two complementary techniques, the ages of 806 female L. sericata, from two farms in the south-west of England, were estimated over a complete field season in 1996. Analysis of median age of these females revealed distinct peaks and troughs over time. The observed periods of low median age corresponded with predicted periods of high adult emergence; the periods of increasing and high median age corresponded with the predicted senescence of the L. sericata population. Hence, by analysis of population age structure, this study supports the view that fluctuations in abundance of L. sericata, observed in the field, represent the emergence and senescence of relatively discrete generations of adults.     

Biological activity of Bacillus thuringiensis strains against larvae of the blowfly Chrysomya putoria (Wiedemann) (Diptera: Calliphoridae)

Different strains of Bacillus thuringiensis Berliner were proved to be a powerful biologic insecticide against larvae of several insect orders. Due to the epidemiological importance of blowflies of the Chrysomya Robineau-Desvoidy genus in the production of secondary cutaneous myiasis and mechanic transmission of pathogenic agents, the performance of two strains of B. thuringiensis (LFB-FIOCRUZ 907 and LFB-FIOCRUZ 856) was tested against larvae of Chrysomya putoria (Wiedemann). The LFB-FIOCRUZ 907 strain was tested in four different concentrations, added to the diet; the LFB-FIOCRUZ 856 strain was tested in three concentrations. C. putoria larvae showed sensibility to the treatment with the LFB-FIOCRUZ 907 strain at the tested concentrations. The higher concentration presented the best efficiency, causing higher mortality and reducing larval weight and adult emergence more intensely. The LFB-FIOCRUZ 856 strain showed low toxicity, slightly reducing emergence time of adults at 326 mg/25 g concentration and larval weight at 326 mg/25 g and 86 mg/25 g concentrations.     

Distinction among the puparia of three blowfly species (Diptera: Calliphoridae) frequently found on unburied corpses

Calliphorid larvae are important in the decomposition of carrion. Since these larvae are present in the primary stages of succession on carcasses, they may be important indicators of death time and the movement of corpses in homicide investigations. In this study we examined the morphological differences among puparia of Chrysomya megacephala, C. putoria and Cochliomyia macellaria. Puparia of the three species (N=30, each) were obtained from the F2 generation bred in culture medium at 25 degrees C, and 60% relative humidity on a 12 h photoperiod. The interspecific differences found were related to the conspicuousness of six tubercles located in the region near the posterior spiracles and to the distance between the two peritrema involving the spiracles. The latter were (mean +/- SD) 15.2 +/- 3.1 microm for C. megacephala, 18.8 +/- 2.8 microm for C. putoria and 16.5 +/- 3.5 microm for C. macellaria. The results of the present study may be useful in forensic entomology.     

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.