THE OLFACTORY BEHAVIOUR OF LUCILIA SPECIES (DIPTERA) UNDER NATURAL CONDITIONS

Using an apparatus of the 'two-choice' type under field conditions, it has been demonstrated that a wool-factor forms an important part of the mechanism whereby female Lucilia sericata may be attracted to sheep. The 'wool-factor' could not wholly be replaced by ammonium- or sulphydryl-type attractants.
L. sericata was strongly attracted by the combination of ammonium carbonate/indole with sheep wool but less strongly attracted when ethyl mercaptan/hydrogen sulphide was used with sheep wool. L. caesar and L. illustris , on the other hand, were not markedly responsive to the ammonium-type attractants but were strongly attracted by the sulphydryl mixture used either alone or in combination with sheep wool.
Temperature is an important element in the oviposition stimulus. The amount of oviposition by L. sericata was increased when substances known to induce oviposition were exposed at 30–40† C.
Sheep wool kept moist and incubated at approx. 38† C. under field conditions for 3 weeks did not attract L. sericata and oviposition did not occur on such wool. This suggests that bacteria normally present on the wool fibre as distinct from the skin, do not play an important part in rendering sheep susceptible to blowfly attack.     

STUDIES ON LUCILIA SPECIES (DIPTERA) UNDER DANISH CONDITIONS

Whilst sheep myiasis caused by Lucilia sericata is a severe economic problem in Great Britain, it rarely reaches such proportions in countries bordering Western Europe. Possible reasons for this relative absence of myiasis were investigated in Denmark.
During the period 19 July-15 August 1948, trapping studies showed that blowflies normally associated with myiasis in Great Britain, and particularly L. sericata , occurred fairly abundantly in the Mols area of Jutland.
The reactions of Danish L. sericata to attractive materials placed on sheep were similar to those shown by the species under British conditions. The number of egg batches laid on sheep in response to chemical stimuli were fewer than would have been expected in Great Britain.
Studies on the fleece microclimate showed that relative humidities of 50 % or more frequently occurred on the skin surface. Humidities 3 cm. above the skin were markedly lower. Except during or immediately after rain, humidities high enough to ensure the hatching of blowfly eggs were never recorded.
It is concluded that the absence of myiasis in Denmark and its relatively low incidence in other countries is not due to the existence on the Continent of a strain of L. sericata differing in oviposition habits from the British species.     

A comparison of Lucitraps and sticky targets for sampling the blowfly Lucilia sericata

The Lucitrap (Miazma Pty Ltd, Queensland, Australia) combined with a synthetic odour bait, Lucilure (Miazma Pty Ltd, Queensland, Australia), is a commercially available trap for sampling and control of Lucilia cuprina (Wiedemann) in Australia. It was tested in Hungary against Lucilia sericata (Meigen) (Diptera: Calliphoridae), a cause of sheep strike throughout temperate Europe. The standard Lucitrap was tested against black or yellow sticky target traps. Both trap types were baited with either Lucilure or liver and 10% w/v sodium sulphide solution. With Lucilure as bait, L. sericata were caught on sticky traps but not in Lucitraps. With liver and sodium sulphide as bait, sticky traps caught 500-1500 times more L. sericata than Lucitraps. An adhesive sheet fitted to the top of a Lucitrap captured 30-300 times more L. sericata then were captured inside an unaltered Lucitrap. Direct observation of metallic green calliphorids (92.1% L. sericata) alighting on Lucitraps indicated that most flies stayed for a short while (modal class 2-4 s) and only a few stayed longer, to an observed maximum of 28 s. Flies explored a mean of 1.5 entry holes (range 0-7) during a visit but only 6% entered the trap. Size of L. sericata was not a physical barrier to Lucitrap entry, because many larger species were captured. However, L. sericata captured inside Lucitraps were significantly smaller than those captured on sticky traps, demonstrating that size was of behavioural importance. The data demonstrate that the Lucitrap is not effective as a trap for L. sericata in Hungary, due mainly to a failure of flies to enter the trap in large numbers. In Australia and South Africa, L. sericata is commonly caught in Lucitraps baited with Lucilure, although L. cuprina is more numerous. Our study highlights the potential for diversity of fly behaviour between different geographical populations of the same species. Such diversity can have a significant effect on the functioning of systems for fly sampling and control, when these systems depend for their success on certain behavioural responses of the target species.     

Orientation of agents of wound myiasis to hosts and artificial stimuli in Hungary

Abstract. The orientation of adults of the myiasis species Wohlfahrtia magnified and Lucilia sericata to artificial visual stimuli (cloth targets) and olfactory stimuli ('swormlure-4', a potent screwworm attractant), was studied in sheep pastures near to Sarbogard in Hungary. Experiments with odour-baited cloth targets, enclosed in electrocuting grids, demonstrated that colour was an important factor influencing catches on targets: a black target caught most flies of both species, with other colours in the following order of effectiveness, blue > white > yellow. Wohlfahrtia magnified did not respond to swormlure-4 in the strong manner that L. sericata did. The sex ratios of W. magnifica caught on targets (67.2% males) and hand-netted from fence posts (68.8% males) were similar and biased towards males, whereas that of L. sericata on targets was strongly biased towards females (15.6% males), indicating a fundamental difference in the response of these two myiasis species towards the swormlure-baited targets. The orientation of these two species towards hosts was also recorded together with that of a third species, Phormia regina . Electric nets placed beside infested sheep caught significantly more flies of all three species than those placed beside uninfested sheep or in the absence of sheep. The sex ratio of W. magnified caught around infested sheep was the reverse of that on targets, with 68.5% females. Wohlfahrtia magnifica responded more strongly to healthy, uninfested sheep than did L. sericata and P. regina . The potential for use of targets both for population monitoring and control is discussed.     

Composition of the surface hydrocarbons from the vitelline membranes of dipteran embryos

Hydrocarbons were the major lipid class extracted by hexane from the vitelline membrane surface of dechorionated eggs of the house fly, Musca domestica, the New World screwworm, Cochliomyia hominivorax, the secondary screwworm, Cochliomyia macellaria, the green bottle fly, Phaenicia sericata, the sheep blow fly, Lucilia cuprina and the Mexican fruit fly, Anastrepha ludens. The length of time the embryos must be exposed to hexane with or without a small amount of alcohol in order to attain permeability was species-dependant. Long-chain n-alkanes comprised the major lipid class removed from vitelline membranes of all species except A. ludens where 2-methylalkanes were the major class. The range in size by the total number of carbon atoms in the hydrocarbons was: C23-C49 in C. hominivorax, C27-C33 in C. macellaria, C24-C35 in L. cuprina, C25-C36 in M. domestica, C25-C33 in P. sericata and C21-C51 in A. ludens. The major hydrocarbon component, expressed as percent of the total hydrocarbons, was n-nonacosane (C29) in C. hominivorax (40%), C. macellaria (43%), L. cuprina (38%), M. domestica (39%) and P. sericata (60%). However, in A. ludens, 2-methyloctacosane (32%) was the major hydrocarbon. Unsaturated hydrocarbons, monoenes (16%) and dienes (11%), were abundant only in A. ludens. Since prior studies indicated that the length of time the embryos must be exposed to hexane with or without a small amount of alcohol in order to attain permeability is species dependant, we suggest that the differences in hydrocarbon composition may contribute to this variation in lipid extractability.     

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 .     

Prasinons A and B: Potent Insecticides from Streptomyces prasinus

Two metabolites which have high activity against sheep blowfly larvae (Lucilia sericata and L. cuprina) were found to be produced by Streptomyces prasinus NCIB 10719. These substances were isolated from culture filtrate by solvent extraction and chromatography and named prasinons A and B. Fermentation factors affecting the formation of these substances are described together with their physical, chemical, and biological properties.     

Analysis of the circadian clock gene period in the sheep blow fly Lucilia cuprina

We have isolated a homologue of the period (per) gene from the Australian sheep blow fly, Lucilia cuprina, as part of a comparative approach to the analysis of dipteran circadian systems. Sequence analysis of the 4 kb per cDNA revealed the conservation of three functional domains, namely the PAS dimerization motif, and the nuclear and cytoplasmic localization domains. A fourth domain, the threonine-glycine (TG) repeat region, is also conserved in L. cuprina per but has been severely truncated. No length variation was found in the TG repeat of L. cuprina or L. sericata collected from several different latitudinal zones. Expression analysis indicated a diel oscillation in per mRNA in LD 12:12 with a period of 24 h and a peak at Zt 12. PER-immunoreactive protein oscillations were also demonstrated, with peak immunoreactivity lagging approximately 3 h behind peak mRNA levels. These results show the existence of a Drosophila-like circadian system in a calliphorid fly. They also provide evidence for the conservation of per function across the Diptera, and confirm the relevance of the Drosophila system as a model for fly circadian rhythms.     

Olfactory attraction to aggregation pheromone is mediated by disti-flagellum of antennal segments in Riptortus pedestris

Riptortus pedestris (Hemiptera: Alydidae) is a serious pest of soybean and sweet persimmon and uses male produced aggregation pheromone, (E)-2-hexenyl (Z)-3-hexenoate, (E)-2-hexenyl (E)-2-hexenoate, and tetradecyl isobutyrate to facilitate food location and recognition by conspecifics. Using electroantennogram (EAG) and greenhouse bioassay, we determined which antennal segment is involved in the detection of their aggregation pheromone. In the first EAG test using individual antennal segments, significant EAG responses to 1:1:1 mixture of the aggregation pheromone were observed only from the disti-flagellum segments of both male and female antennae at both pheromone doses tested (1 µg and 100 µg). In the following EAG tests using gradually removed antennal segment(s), EAG response was still maintained when the distal half of a disti-flagellum was surgically removed, while EAG response was lost when whole segment of disti-flagellum or other whole segments were gradually removed from intact antenna of both sexes. In greenhouse experiment, removing one or both segment(s) of disti-flagellum from male or female antennae resulted in significant reduction in their attraction to the aggregation pheromone. Together, these findings support that the disti-flagellum of R. pedestris houses olfactory neurons associated with attraction to their aggregation pheromone.     

Blowfly succession from possum (Trichosurus vulpecula) carrion in a sheep-farming zone

The significance of brushtail possum, Trichosurus vulpecula Kerr (Diprotodontia: Phalangeridae) carcasses to the succession and production of Diptera species and its relevance to fly strike management in Tasmania, Australia was examined. Calliphora stygia (Fabricius), Lucilia sericata (Meigen) and Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) were found to be the most abundant and Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae) always the least abundant (< 1%) of the putative primary fly invading species to emerge. Carcasses that were left for up to 15 days in the field before being exposed to flies for 2 days also acted as breeding sites for large numbers of all primary fly species, with the exception of L. cuprina. Ordination analysis revealed no relationship between possum carcasses according to their length of exposure but did show significant negative associations between the number of putative secondary invaders (Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae), Chrysomya varipes (Macquart) (Diptera: Calliphoridae) and putative tertiary flies (Hydrotaea rostrata Robineau-Desvoidy (Diptera: Muscidae)) to the number of C. vicina or C. stygia to emerge. There was enormous variability in the numbers of secondary/tertiary fly species to emerge from carcasses (0-11 450) that negatively correlated with the proportion of all flies to emerge that were primary, and with the mean size of adult L. sericata. Although carcass temperatures, especially those with a large larval population, were elevated, this did not appear to result in significant pre-adult fly mortality. The most important primary fly strike species L. cuprina was only found in insignificant numbers, whereas three other members of the fly strike fauna C. stygia, L. sericata and Ch. rufifacies did use possum carrion as an important breeding resource, but left implications for fly strike management inconclusive.     

Responses of the sheep blowflies Lucilia sericata and Lcuprina to odour and the development of semiochemical baits

Abstract. The literature relating to the attraction of the sheep blowflies Lucilia sericata and Lucilia cuprina to their ovine hosts is reviewed. The responses of the two species are similar and different components of the behaviour leading to host location and oviposition appear to involve at least two distinct sets of semiochemical cues. Activation, upwind orientation and landing appear to occur in response to putrefactive sulphur-rich volatiles, originating from bacterial decomposition products. Oviposition is elicited primarily by the presence of ammonia-rich compounds; moisture, pheromones and tactile stimuli may also act as oviposition stimuli. There is a pronounced sex difference in the response of Lucilia to semiochemicals with a higher proportion of females attracted than males and a higher proportion of gravid than non-gravid females. While the mechanisms of host location by Lucilia are of intrinsic interest, understanding the responses to semiochemicals is important in the attempt to develop powerful synthetic baits for deployment with the traps or targets used for population sampling or suppression. The literature is discussed with respect to the development of synthetic semiochemical baits.     

Flies in the ointment: a morphological and molecular comparison of Lucilia cuprina and Lucilia sericata (Diptera: Calliphoridae) in South Africa

Abstract.  Complementary nuclear (28S rRNA) and mitochondrial (COI) genes were sequenced from blowflies that phenotypically resembled Lucilia cuprina (W.), Lucilia sericata (Meigen) or exhibited characters of both species. The aim was to test a long-held hypothesis that these species hybridize under natural conditions in South Africa ( Ullyett, 1945 ). Blowflies were obtained predominantly from the Cape Town metropolitan area, but reference samples were acquired for L. sericata from Pretoria. Several L. cuprina -like flies were shown to possess a conflicting combination of nuclear and mitochondrial genes that has also been seen in Hawaiian specimens. Homoplasy, sampling of pseudogenes, hybridization and incomplete lineage sorting are discussed as possible hypotheses for the pattern and the latter is concluded to represent the most likely explanation.     

Seasonal and spatial changes in blowfly production from small and large carcasses at Durham in lowland northeast England

Colonization by blowflies (Diptera: Calliphoridae) of mouse carcasses exposed in open agricultural land near Durham (54 45'N) changed from early spring monopolization by Calliphora vicina R.-D. to a summer pattern of multiple species exploitation by this species together with Lucilia caesar L., L. illustris Mg., L. silvarum Mg., L. sericata Mg. and L. richardsi Collin. In a garden at the edge of Durham, mouse carcasses were dominated by C. vicina from spring to autumn. Difference in mouse colonization between the agricultural and garden sites seemed to reflect differences in the blowfly species present, as measured by baited trap catches at the sites. In sets of C. vicina reared from mice under conditions of competition for larval food, it was found that resulting females were significantly larger than males, size being measured as mean wing length. Blowfly production from three sheep carcasses exposed successively at the agricultural site was dominated by C. vomitoria L. and L. caesar, but also produced other Lucilia species in small numbers, including L. sericata. These L. sericata females from sheep that had died from causes other than myiasis included full-sized specimens, in contrast to those produced from mouse carcasses that were all undersized individuals. As L. sericata females trapped on sheep pastures are predominantly full-sized, this suggests that large carcasses may, in part, be a source of the L. sericata population that attacks sheep as a myiasis agent. The nature of large carcasses as possible sources of L. sericata in lowland Britain is discussed.     

Electrophysiological responses of antennal receptor neurons in female Australian sheep blowflies,Lucilia cuprina,to host odours

Studies were conducted to investigate the electrophysiological responses of receptor neurons on the antennae of female Lucilia cuprina to putative stimulants. Three distinct types of olfactory neurons were identified. Tests with 25 compounds showed 27 out of the 75 neurons examined responded best to racemic 1-octen-3-ol (Oct-best neuron), nine to dimethyldisulphide (DMDS-best neuron) and seven to 2-phenylethanol (PE-best neuron). The remaining cells were not stimulated by any chemical stimulus presented in this study. The olfactory neurons showed low spontaneous activities, 2.2 ~ 2.7 impulses/s, which increased significantly on stimulation with test compounds. Dose-dependent responses were observed with Oct-best neurons. Another type of neuron that had a much higher spontaneous activity (26 impulses/s) was observed. This neuron did not respond to any of the candidate compounds tested but showed a decrease in activity with increased airflow over the antennae and was termed the Airflow-sensitive neuron. The spontaneous activities of Oct-, DMDS-, PE-best and Airflow-sensitive neurons were inhibited by butanoic, pentanoic, hexanoic acids, and 3-methylindole.     

Heterorhabditis spp. and Steinernema (= Neoaplectana) spp.: temperature, and aspects of behavior and infectivity

The infectivity of several species/strains of nematodes of the genera Heterorhabditis and Steinernema for postfeeding, 3rd instar larvae of the sheep blowfly, Lucilia cuprina, was tested in sand at various temperatures. Of the two genera, the steinernematids were more active at lower temperatures and parasitized L. cuprina over a greater temperature range. The temperature range of infectivity for L. cuprina differed between nematodes of the same genus and between strains of the same species. Parasitization of L. cuprina and Galleria mellonella occurred in a temperature range that was greater than that permitting nematode development and reproduction. Different strains of the same species were found to have different temperature limits for development and reproduction. Developmental rate was different for each nematode species tested with the heterorhabditids taking longer to complete their life cycle than did the steinernematids.     

Development of an attractive target for the sheep blowfly Lucilia sericata

Coloured, odour-baited, sticky targets, designed to catch the sheep blowfly Lucilia sericata Meigen are described and the results of field trials are presented. The number of L. sericata caught by the targets was positively related to target surface area and was dependent on target colour. The performance of the coloured targets is described by a model in which catch is related negatively to reflectivity in the 300-450 nm (ultra-violet/blue) band of the spectrum and positively to the reflectivity in the 450-580 nm (blue-green-yellow) band. Of the Lucilia blowflies caught by the targets, 13-16% were L.sericata and 72-75% of the L.sericata were female. The number of L.sericata caught appeared to be positively related to the availability of sheep over a relatively localized area and showed a marked decline following insecticidal dipping of sheep. The further development of targets and the implications of the results for L.sericata control are discussed.     

mtDNA中COⅠ分子标记在常见食尸性蝇类鉴定中的应用

死后不同时间,在尸体上出现不同种类食尸性蝇类的演替规律,可用于准确推断死亡时间。传统上仅依据蝇类形态学特征来判断种属,但由于蝇类的形态结构复杂和种间形态差异微小等特点,对蝇类尤其是对蝇类幼虫的种属鉴别很难。因此应用分子生物学方法对食尸性蝇类及其幼虫进行种属鉴定非常重要。本研究主要是利用此方法对我国西部部分地区常见双翅目食尸性蝇类包括：开普黑蝇、大头金蝇、丝光绿蝇及部分卵,铜绿蝇、棕尾别麻蝇及部分幼虫和蛹的线粒体DNA(mtDNA)上细胞色素氧化酶辅酶Ⅰ(COⅠ)中278 bp的基因序列进行鉴别。除个别蝇类如丝光绿蝇与铜绿蝇外,该方法均能有效地将上述食尸性蝇类鉴定到种属水平。在我国,它将成为法医鉴别食尸性蝇类种属的可靠依据。     

Quantifying relative importance of maxillary palp information on the olfactory behavior of Drosophila melanogaster

Maxillary palps have been proposed as secondary olfactory organs, after the antennae, in Drosophila melanogaster. Our study tries to establish the quantitative importance of both organs as olfactory information mediators. Dose-response curves for three odorants: ethyl acetate, propionaldehyde and benzaldehyde were carried out for comparing olfaction in either complete animals or flies surgically deprived of antennae. Antennaless flies tested in our behavioral assay showed indifferent, attractant and repellent responses depending on concentration, similarly as normal flies do. However, they clearly displayed less sensitivity than normal flies. The range of concentrations they were able to perceive was correlated to antennal sensitivity approximately by a factor 110 for ethyl acetate and benzaldehyde, and between 110 and 1100 at high concentrations of propionaldehyde. A complementary experiment was performed to test changes in olfactory behavior produced by removing maxillary palps in the presence of antennae. At high concentrations of odorant, responses to ethyl acetate and propionaldehyde experienced small changes when both palps were removed. Results are compatible with a summation model of all olfactory information reaching the brain either through antennae or palps.Abbreviations ANOVA analysis of variance - EAG electroantennogram, extracellular recording of electrical changes produced on the antenna in response to odorant stimulation - EPG electropalpogram, extracellular recording of electrical changes produced on the maxillary palp in response to odorant stimulation - IO Olfactory index     

Retarded growth of Lucilia cuprina larvae on sheep and their sera following production of an immune response.

Attempts were made to immunize sheep against larvae of the sheep blowfly Lucilia cuprina using supernatant and pellet prepared by centrifuging (100,000 g max) homogenates from whole second instar larvae of L. cuprina or their excised guts. Injection of supernatant from whole larvae and from two fractions of this supernatant, prepared by ammonium sulphate precipitation, significantly reduced (by 24-58%) the final weight of larvae grown in vivo (i.e. on immunized sheep) for 20 or 44 h. Serum from animals vaccinated with supernatant from whole larvae reduced larval weights by 12% after growth for 20 h in vitro (i.e. on diet containing serum from treated animals). Pellet material from whole larvae or guts, when injected into sheep, stimulated an immune response which reduced the weight of larvae by 20-23% after 20 or 48 h in vitro. Larvae grown on these animals were not reduced in weight. Immunoglobulin (Ig) isolated from serum of a sheep vaccinated with gut material strongly retarded growth of larvae in vitro, the effect increasing with Ig concentration. These results indicate that an immune response in sheep, induced by injecting extracts of L. cuprina larvae, substantially reduces growth of this parasite.     

Antennal Asymmetry in Social Behavior of the Australian Stingless Bee, <Emphasis Type="Italic">Tetragonula carbonaria</Emphasis>

The left and right antennae of stingless bees have different roles in learning and recall of olfactory memory. Antennal asymmetry in social behavior is reported here. Approaches and physical contacts were scored in dyads of stingless bees (Tetragonula carbonaria): dyads in which both bees had only their right antennae (left antennae removed) made significantly more physical contacts with each other than dyads in which both bees had only their left antennae. In dyads of one left and one right, it was found, unexpectedly, that the bee with a left antenna approached the bee with the right antenna more often that the other way around, and the bee with the left antenna often attacked (by biting) its hive mate. Hence, the low number of contacts in dyads of bees using their left antennae appears to be due to mutual avoidance. Whereas use of the right antenna stimulates positive contact, the left stimulates avoidance or attack. Via such left-right asymmetries, intact bees may compute behavior directed towards friend and foe. Such antennal asymmetry may have evolved concomitantly with eusocial behavior. We found no evidence that it was associated with significant differences in the number of olfactory or non-olfactory sensilla on the left versus right antenna.