Noppawan Boonchu

First Report of Human Myiasis Caused by Chrysomya megacephala and Chrysomya rufifacies (Diptera: Calliphoridae) in Thailand, and Its Implication in Forensic Entomology

Abstract 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, ≈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.

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.

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.

Larval Morphology of Chrysomya nigripes (Diptera: Calliphoridae), a Fly Species of Forensic Importance

Abstract 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.

Hairy Maggot of Chrysomya villeneuvi (Diptera: Calliphoridae), a Fly Species of Forensic Importance

Abstract 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. villeneuvi 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.

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 Coeloconic Sensilla on Postpedicel and Maxillary Palp of Megaselia scalaris (Diptera: Phoridae)

Abstract The external morphology of coeloconic sensilla (peg-like sense organs protruding from deep pits) on the postpedicel (third antennal segment) and maxillary palp from a female Megaselia scalaris (Loew) is described using scanning electron microscopy. The pegs of the sensilla located on the postpedicel are “starfruit-like” in shape and are completely contained within deep depressions. Transmission electron microscopy showed that each peg has a thick and nonporous wall. The coeloconic sensilla of the maxillary palps are long, linear, and blunt-tipped and protrude over the cuticular surface. Possible functions of the sensilla are discussed.

Ultramorphology of Eggshell of Flesh Fly Liosarcophaga dux (Diptera: Sarcophagidae)

Abstract Eggs of Liosarcophaga dux (Thomson) (Diptera: Sarcophagidae) are elongated and slightly bean-shaped, measuring ≈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.

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.

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.