The forensic entomology case described herein is the first such case documented in Thailand. A mummified corpse of a 32-yr-old man was discovered in a forested habitat, with the larvae of six species of flies (Diptera) found in association with the corpse at the time of its discovery, i.e., those of Hydrotaea (=Ophyra) spinigera Stein (family Muscidae), Piophila casei (L.) (family Piophilidae), Megaselia scalaris (Loew) (family Phoridae), Sagus sp. (family Stratiomyidae), and larvae of two unidenitified flesh fly species (family Sarcophagidae). The presence and age of the larval specimens of P. casei, M. scalaris, and H. spinigera gave entomological evidence that the postmortem interval for the corpse was 3-6 mo. This report also documets some of the forensically important fly species that occur in Thailand.

The surface ultrastructure of all larval instars of Chrysomya rufifacies (Macquart) is described by means of scanning electron microscopy (SEM). Morphological changes were greatest from the first to the second instar, but less from the second to the third instar. Most of these changes involved the structure of the anterior spiracle, posterior spiracle, integument of the body, and mouthhooks. Modification of the mouthhooks, especially in the third instar, are helpful in explaining the ferocious feeding ability of the older maggots. The common name of "hairy-maggot" for C. rufifacies is only appropriate for the second and third instars because of their elongated tubercles along the body, whereas this name is not descriptive of the first instar that lack tubercles.

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 closelyrelated species.Key words: Megaselia scalaris -ultrastructure -third-instar -scanning electron microscopy -forensic entomology Megaselia scalaris (Loew), humpbacked fly, is an insect of medical importance worldwide. In addition to causing myiasis in humans (Trape et al. 1982, Singh et al. 1988, Singh & Rana 1989, it has also been reported as a forensically-important fly (e.g. Barnes 1990, Disney 1994. Larvae of this species have more recently been reported from both exposed human corpses and within a tightly sealed corpse (Greenberg & Wells 1998). Thus, the identification of this fly larva to species is mandatory to improve the accuracy of a forensic investigation, if this larva is present in a corpse and could be used as entomological evidence.The immature and adult stages of M. scalaris have been previously described based on light microscopy (Zumpt 1965, Tumrasvin et al. 1977, Kaneko et al. 1978, Liu & Greenberg 1989, and scanning electron microscopy (SEM) has been used to describe the egg (Greenberg & Wells 1998). We report, herein, some details of the surface ultrastructure of the third-instar M. scalaris with the aid of SEM. Particular attention was given to the morphology of the cephalic segment, anterior and posterior spiracles, in order to point out some taxonomic significance from the other Megaselia species.The third-instar M. scalaris, which was obtained from wild-caught females that came to lay eggs in a tray baited with fresh pork liver, was set up in the Department of Parasitology, Faculty of Medicine, Chiang Mai University, Thailand. The eggs were identified as M. scalaris according to the morphological features demonstrated by Greenberg and Wells (1998 from the egg, it was reared with fresh pork liver until reaching the third-instar. Some larvae were collected from the colony and washed several times with normal saline solution. They were killed by placing in hot water (≈70°C) for a few min and then fixed in a fixative agent consisting of 2.5% glutaraldehyde at 4°C for 24 h. The fixed larvae were then subjected to postfixation in 1% osmium tetroxide and dehydration in a graded alcohol series that was followed by treatment in acetone and critical-point drying. They were then mounted on stubs, sputter-coated with gold, and viewed with a JEOL-JSM840A scanning electron microscope. Photomicrographs were made using Kodak® Verichrome Panchromatic film VP 200.The third-instar M. scalaris is creamy white and ≈4 mm in length.

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