Ultramorphology of eggshell of flesh fly Liosarcophaga dux (Diptera: Sarcophagidae).

Eggs of Liosarcophaga dux (Thomson) (Diptera: Sarcophagidae) are elongated and slightly bean-shaped, measuring approximately 1.5 mm in length. Each is covered externally by an eggshell comprised of polygonal patterns. In this study, scanning and transmission electron microscopy were used to examine the eggshell of this species of flesh fly for the first time. No plastron region or median area was detected. Ultrathin sectioning of the eggshell revealed multiple layers in the shell that could be observed using transmission electron microscopy.

Larval morphology of Chrysomya nigripes (Diptera: Calliphoridae), a fly species of forensic importance.

The morphology of all instars of Chrysomya nigripes Aubertin, a blow fly species of forensic importance, is presented with the aid of both light microscopy and scanning electron microscopy (SEM). Morphological features of the cephalopharyngeal skeleton, anterior spiracle, posterior spiracle, and dorsal spines between the prothorax and mesothorax are highlighted. No consistent features were found, even using SEM, for distinguishing the first instar of C. nigripes from that of Chrysomya megacephala (F.) or Chrysomya rufifacies (Macquart), two other commonly associated blow fly species in corpses in Thailand. Several features observed in second and third instars proved to be valuable characteristics for separating these species.

First report of human myiasis caused by Chrysomya megacephala and Chrysomya rufifacies (Diptera: Calliphoridae) in Thailand, and its implication in forensic entomology.

We report a forensic entomology case associated with human myiasis in Chiang Mai Province, northern Thailand. The remains of a 53-yr-old-male were concurrently infested with third instars of the two blow fly species, Chrysomya megacephala (F.) and Chrysomya rufifacies (Macquart), near a severe tumor lesion presented on the lower right leg. The presence of third instars, approximately 5 d old, on the day following postmortem indicated that myiasis occurred before death. This is the first report of both fly species acting as a myiasis-producing agent in Thailand. Unsynchronized data between the age of fly larvae due to myiasis premortem and verified age/ condition of the corpse suggest a potential complication and error in the estimation of postmortem interval if other predisposition fly infestations are not considered.

Morphology of second and third instars of Chrysomya villeneuvi Patton (Diptera: Calliphoridae), a fly species of forensic importance.

The morphology of the second and third instars of Chrysomya villeneuvi Patton, a fly species of forensic importance, was presented by use of light microscopy. Both instars were of hairy appearance, bearing elongated tubercles along the abdominal and caudal segments. The anterior spiracle had 13-15 papillae. Minute dark spots were observed to thoroughly cover the tubercle's surface, with 4-6 strong dark tips. Regarding the third instar, the intersegmental spines between the prothorax and mesothorax were heavily pigmented. The posterior spiracle had a thick and heavily pigmented incomplete peritreme. The surface and tip of the tubercles was covered with heavily pigmented sharp spines. The integument of the body was covered with numerous distinct net-like patches. A comparison with another well-known hairy maggot, Chrysomya rufifacies (Macquart), was discussed.

Hairy maggot of Chrysomya villeneuvi (Diptera: Calliphoridae), a fly species of forensic importance.

We reported on the hairy maggot of Chrysomya villeneuvi Patton, collected from a human corpse in Thailand. Although the general morphology of the third instar closely resembled the more common hairy maggot blow fly, Chrysomya rufifacies (Macquart), the spines along the tubercles of each body segment could be used as a feature to distinguish between these species, with those of C. villeneuri bearing sharp-ended spines that encircle the entire tubercle. Not only has the resemblance of a hairy appearance between C. villeneuvi and C. rufifacies larvae been documented but also their similarity in predacious feeding behavior. The differentiation between these two species is necessary for post-mortem interval estimation in the corpse.

Mouthparts of Megaselia scalaris (Loew) (Diptera: Phoridae).

Mouthparts of adult Megaselia scalaris (Loew), a fly species of medical importance, were examined using scanning electron microscopy. Sexual dimorphism of the labellum was observed in the mouthpart structures of this species. The labella of males were clothed with a dense covering of microtrichia, but these were found to be entirely absent from the labella of females. Aside from this difference, trichoid and conical sensilla that are most likely used as taste or contact chemoreceptors appear on the labellum and labrum of both sexes. In addition, five pairs of sharply pointed teeth at the ventral surface of the labellum is another feature that is shared by the two sexes. A plausible feeding mechanism for this fly is also advanced.

Larval ultrastructure of Parasarcophaga dux (Thomson) (Diptera: Sarcophagidae).

Ultrastructure of all larval instars of Parasarcophaga dux (Thomson), a common flesh fly species in Thailand, is presented using scanning electron microscopy. Special attention is given to the structure of anterior and posterior spiracles since these are important features used to differentiate between other sarcophagids. Each anterior spiracle in second and third instars has a single row of papillae varying in number from 14 to 17. The posterior spiracular discs have incomplete peritremes, with a prominent inner arc. Three long, narrow spiracular slits are oriented more or less vertically in each spiracular disc of third instar. Posterior spiracular hairs lack extensive branching and emanate approximately midway down the length of each slit. Microscopic morphology of the mouthhooks markedly differs between the first and second instars. The structure of these mouthhooks supports this fly species as being necrophagous or capable of producing myiasis.

Prestomal teeth of some flies of medical importance.

Comparison of prestomal teeth of adult Chrysomya megacephala, Chrysomya rufifacies, Chrysomya nigripes, Lucilia cuprina, Parasarcophaga dux and Musca domestica was accomplished by use of scanning electron microscopy. The prestomal teeth of C. megacephala, C. rufifacies, L. cuprina and P. dux are all similar in appearance in having various degrees of bifurcation at their tips. In contrast, the tips of the prestomal teeth in C. nigripes are very shallowly serrated, but are comparatively more deeply serrated in M. domestica. These features may help account for the roles these flies may play in matters of medical or veterinary importance, such as causing physical irritation or acting as vectors of disease agents.

Identification of forensically important fly eggs using a potassium permanganate staining technique.

Fly eggs found in corpses can be utilized as entomological evidence in forensic investigations of deaths if the species of fly and the developmental rate at a temperature similar to the death scene are known. The species identification of fly eggs is particularly important, and previously, scanning electron microscope has been used for this purpose. Herein, we report a simple technique, using light microscopy, to identify forensically important eggs of Chrysomya rufifacies (Macquart), Chrysomya megacephala (Fabricius), Chrysomya pacifica Kurahashi, Chrysomya nigripes Aubertin, Aldrichina grahami (Aldrich), Lucilia cuprina (Wiedemann), Musca domestica L. and Megaselia scalaris (Loew). A 1% potassium permanganate solution was used to stain egg surfaces for 1 min, followed by dehydration in 15, 70, and 95%, absolute alcohol (each solution for 1 min) and the eggs were permanently mounted. The characteristics are based on the width of plastron, morphology of plastron area surrounding the micropyle and chorionic sculpturing, with the length of egg being used as supplemental feature.

Antennal sensilla of some forensically important flies in families Calliphoridae, Sarcophagidae and Muscidae.

Antennal sensilla of some forensically important fly species in the families Calliphoridae (Chrysomya megacephala, Chrysomya rufifacies, Chrysomya nigripes and Lucilia cuprina), Sarcophagidae (Parasarcophaga dux) and Muscidae (Musca domestica) were studied using scanning electron microscopy. Five types of sensilla were observed: trichoid, basiconic, coeloconic, styloconic and sensory pit. Only trichoid sensilla are found on the scape of the antenna, while both trichoid and styloconic sensilla are located on the antennal pedicels of all species studied. Basiconic sensilla are the most numerous of the sensilla found on the antennae of both sexes of all fly species studied and are comprised of two subtypes: large and small basiconic sensilla. Coeloconic sensilla are characterized by short pegs, with either grooved or smooth surfaces, that are sunken into deep depressions. No marked difference was observed in the number, morphological structure or distributional pattern of any of the sensilla among the species studied, with the exception of there being more numerous sensory pits detected in female P. dux compared to the other species. The suggested function of each antennal sensillum was based on comparison with results of other investigations on similar sensilla.

Some ultrastructural superficial changes in house fly (Diptera: Muscidae) and blow fly (Diptera: Calliphoridae) larvae induced by eucalyptol oil.

The ultrastructural superficial changes in third instar house fly (Musca domestica) and blow fly (Chrysomya megacephala) induced by eucalyptol oil were observed using scanning electron microscopy. Dipped in 0.902 g/ml eucalyptol for 30 sec, the larvae integument of both species showed significant aberrant appearance of the body surface, particularly swelling integument, bleb formation, partial breach and deformation of spines.

Effects of eucalyptol on house fly (Diptera: Muscidae) and blow fly (Diptera: Calliphoridae).

The effects of eucalyptol were evaluated against the house fly, Musca domestica L., and blow fly, Chrysomya megacephala (F.). The bioassay of adults, using topical application, indicated that M. domestica males were more susceptible than females, with the LD50 being 118 and 177 microg/fly, respectively. A higher LD50 of C. megacephala was obtained; 197 microg/fly for males and 221 microg/fly for females. Living flies of both species yielded a shorter life span after being treated with eucalyptol. The bioassay of larvae, using the dipping method on the third instar, showed that M. domestica was more susceptible than C. megacephala, with their LC50 being 101 and 642 microg/microl, respectively. The emergence of adults, which had been treated with eucalyptol in larvae, decreased only in M. domestica. Having the volatile property, fumigation or impregnated paper test of eucalyptol or the efficacy of repellence or attractiveness merits further investigations to enhance bio-insecticidal efficacy.

Observations on first and second-instar larvae of Megaselia scalaris (Loew) (Diptera: Phoridae).

The ultrastructure of the first and second-instar larvae of Megaselia scalaris (Loew) was studied using scanning electron microscopy (SEM). Significant changes in morphological features were observed in the anterior and posterior spiracles, but only minimal changes in the labium and mouthhooks were seen. The ultrastructure of M. scalaris larvae not only provides chronological transformation of their larval instars, but it can also be used to explain their feeding behavior and mode of respiration. In addition, morphological structures useful for specific identification of first or second-instar larvae collected from human corpses may be used in forensic investigations.

Larval morphology of Chrysomya megacephala (Fabricius) (Diptera: Calliphoridae) using scanning electron microscopy.

The larval morphology of Chrysomya megacephala (Fabricius) is presented using scanning electron microscopy (SEM). Extreme similarity of this species to Chrysomya rufifacies (Macquart), a species usually found concurrently inhabiting decomposing human corpses in Thailand, is seen only in the first-instar larvae. The relative thickness of the branches of the posterior spiracular hairs in these species could be used to differentiate them in this developmental stage. In contrast, the "hairy" appearance of C. rufifacies allows second- and third-instar larvae to be easily distinguished. Results of this study should help in future endeavors to differentiate C. megacephala from other larvae found in decomposing human corpses in Thailand.

Comparison of the effectiveness of baits used in traps for adult fly collection.

The effectiveness of 6 different baits used in fly traps for adult fly collection was compared in October-November, 2000, near the cafeteria of Maharaj Nakhon Chiang Mai Hospital, Chiang Mai Province, northern Thailand. The baits used were fresh viscera (pork, beef and fish) and fresh meat (pork, beef and fish), with 500 g of each kind being used in each fly trap for each experiment. All were replicated four times. Pork viscera yielded the highest effectiveness (35.2%), followed by fish meat (30%). Four other kinds of bait showed relatively low efficiency, ie fish viscera (12.0%), beef viscera (9.0%), pork meat (8.4%) and beef meat (5.4%). The calliphorid Chrysomya megacephala was the most abundant fly species collected, while sarcophagids and muscid flies were found in much smaller numbers. The number of females was higher than males in all collections. Although all baits used were parts of animal carcasses that were very attractive for adult flies to feed upon and oviposit, the result of this study showed the differences in their effectiveness for fly collection, particularly during the late rainy season to early winter in Chiang Mai. Pork viscera showed the highest efficacy for metallic fly collection, but not for all species. Further study of suitable baits for the medically important fly species that exist in urban areas should, therefore, be performed.

Surface ultrastructure of third-instar Megaselia scalaris (Diptera: Phoridae).

We describe some ultrastructure of the third-instar Megaselia scalaris (Diptera: Phoridae) using scanning electron microscopy, with the cephalic segment, anterior spiracle and posterior spiracle being emphasized. This study provides the taxonomic information of this larval species, which may be useful to differentiate from other closely-related species.

Ultrastructure of eggshell of Chrysomya nigripes Aubertin (Diptera: Calliphoridae).

We examined the eggshell structure of the blowfly, Chrysomya nigripes Aubertin, a species of forensic importance, using scanning electron microscopy. A relatively wide plastron region was located dorsally. It extended almost the entire length of the egg and bifurcated slightly, close to the micropyle, which is a deep cavity surrounded by an elevated, fine, wavy rim. The chorionic sculpture had an hexagonal pattern, with a smooth and elevated boundary. The ruptured eggshell showed the outermost exochorion, membranous outer endochorion and pillar layer, which also had an hexagonal pattern on a perforated mesh pillar layer. This study provides a greater database on the egg of this forensically significant blowfly.

Fine structure of the eggs of blowflies Aldrichina grahami and Chrysomya pacifica (Diptera: Calliphoridae).

We report here the fine structure of the eggs of blowflies Aldrichina grahami (Aldrich) and Chrysomya pacifica Kurahashi. For A. grahami, the plastron is wide and extends to almost the entire length of the eggs. The plastron near the micropyle is truncated. The polygonal patterns of chorionic sculpture bear a distinct swollen boundary. Regarding C. pacifica, the plastron is narrow and extends to almost the entire length of the eggs. The plastron near the micropyle bifurcates to a Y-shape, but the arms of the 'Y' are short. Information presented herein allows some distinctive features to differentiate among eggs of blowfly species.

Effects of eucalyptol on house fly (Diptera: Muscidae) and blow fly (Diptera: Calliphoridae)

Foram avaliados os efeitos do eucaliptol contra a mosca doméstica, Musca domestica L. e a mosca varejeira, Chrysomya megacephala (F.). O bioensaio de adultos, usando-se aplicação tópica, indicaram que os machos da M. domestica eram mais susceptíveis que fêmeas, com LD50 sendo 118 e 177 µg/mosca, respectivamente. Foi obtido mais alto LD50 da C. megacephala; 197 µg/mosca para machos e 221 µg/mosca para fêmeas. Moscas vivas de ambas espécies tiveram vida menor após tratamento com eucaliptol. O bioensaio de larvas, usando o "dipping method" no terceiro estágio, mostrou que M. domestica foi mais susceptível que C. megacephala com seu LD50 sendo 101 e 642 µg/µl, respectivamente. A emergência de adultos, que tinham sido tratados com eucaliptol na larva diminuiu somente na M. domestica. Tendo propriedade volátil, fumigação ou teste do papel impregnado por eucaliptol ou a eficácia de repelência ou de atração merecem investigações posteriores para aumentar a eficácia do bio-inseticida.

Surface ultrastructure of third-instar Megaselia scalaris (Diptera: Phoridae)

We describe some ultrastructure of the third-instar Megaselia scalaris (Diptera: Phoridae) using scanning electron microscopy, with the cephalic segment, anterior spiracle and posterior spiracle being emphasized. This study provides the taxonomic information of this larval species, which may be useful to differentiate from other closely-related species