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Several types of insect attack on sea turtles have been reported, including attacks on eggs and hatchlings by flies (Andrede et al., 1992; Lopes, 1982; Lopez Barbosa, 1989), on eggs by coleoptera (Lopez Reyes and Bautista Huerta, 1991), on eggs by ants (Subba Rao, 1995; Mortimer, 1990; Duran Naiera, 1990) and on adult females by hematophagous insects (Fretey, 1989). In this study, the carcass of an adult female leatherback turtle (Dermochelys coriacea Vandelli 1761) was observed for one week in a shaded, grassy area of the nesting beach at Yalimapo, French Guiana. The study began on 28 June 1996, when the fresh carcass of a turtle, apparently entangled and drowned in the ropes of an Amerindian boat, was found washed ashore. No open wounds were visible.

In order to facilitate a study of the arrival of necrophagous insect assemblages, as well as their capture, the grass surrounding the carcass was cleared to 1 m away, exposing the sand. During the observation of the progressive decomposition of the turtle under the action of various necrophagous organisms, two types of imago samples were collected approximately every three hours: (1) insects walking on the ground or on/in the carcass and (2) insects flying within the cleared range. Flying insects were killed with a quick spray of insecticide.

On the first morning, the eyes of the leatherback were gouged out by a group of black vultures (Coragyps atratus). By 1100 hr, the bleeding sockets were invaded by ovipositioning flesh flies (Sarcophagids). At 1500 hr, both flesh flies and blow flies (Calliphorids) were ovipositioning in the limb articulations. At several different times on the following day, Coleoptera (Scarabeids and Carabids), were observed along with the first two families. That night, cockroaches (Blattodea) and tenebrionid beetles appeared.

On the third day, all four limbs had noticeably collapsed and the skin had cracked, offering new ovipositional sites for the flies. By 1500 hr, the omnipresent black vultures had pecked six openings into the shell. Under the effect of the sun, fats drained from the adipose tissues. For the first time, anthomyiid flies were observed at the carcass. At 1800 hr, two new holes had been pecked, one toward the edge of the shell, the other in one of the forelimbs. Histerid and staphylinid beetles were captured. At nightfall, maggots emerged from the holes, using the body fats to help them migrate over the surface of the carapace. That evening (2100 hr), cockroaches reappeared and the entire forebody was covered with maggots.

Later that night, after a heavy rain, the entire surface of the sea turtle was covered with maggots, and one cricket (Gryllidae) was captured. Early the next morning, ñ30 black vultures were busy at the carcass. A 0900, 1300 and 1500 hr, calliphorid and anthomyiid flies were observed, and again some histerid and tenebrionid beetles. At 1800 hr, a single heteropter (a cydnid) was observed. On the fifth morning, several of the turtle's eggs had been scattered by the black vultures. Histerids were observed near the decomposing eggs. As on the second day, scarabeids reoccured on the carcass. Toward 1600 hr a soldier fly (Stratiomyidae) appeared for the first time, and remained until 5 July.

On the seventh day, the body cavity was almost entirely emptied and the bones, "picked clean", became visible. The insects observed belonged mainly to the Orders of Diptera and Coleoptera. The others (Dictyoptera, Orthoptera, Heteroptera) were far less frequent and it is difficult to evaluate their role in relation to the carcass. The omnivorous cockroaches could just as easily have fed on dead organic matter as live larva. Only one specimen of Heteroptera was captured and it belonged to the root-feeding cydnid family. Its presence was therefore probably not due to the sea turtle carcass. It is likely that the presence of a phytophagous cricket was equally accidental.

Blow fly and flesh fly larva are almost exclusively necrophagous. Both arrived on the carcass at nearly the same time; that is, once the vultures had provided ovipositional sites suitably sheltered from the sun. It is worth noting that while in our study flesh flies slightly preceded blow flies, in temperate climates, it is blow flies that are usually among the first necrophagous insects to arrive (Leclerc, 1978). Intense competition at these sites due to over-population forced larva to migrate to less exploited areas of the turtle. Rain and draining body fats seemed to aid the mostly nocturnal migration.

Three other families, occuring less frequently, appeared well after the first two. These included anthomyiids on the fourth day, stratiomyids on the fifth, and muscids on the seventh. The biology of these families is poorly known, but it would seen they played a not insignificant role in the decomposition of the carcass. As for stratiomyids, larva were also discovered under the plastral plates of a green turtle carcass on Aztec beach, 30 km south~ east of Yalimapo. The carcass consisted of only a few scattered bones and a dried, empty carapace. Larva were hidden between the plastral plates and the fat-stained sand. These larva should therefore be considered saprophagous rather than necrophagous.

According to Leclerc (1978), necrophagous arthropods, which vary depending on climate and geographical zone, can actually be divided into four categories: (1) the necrophagous (Diptera, Coleoptera, Lepidoptera, Acarids); (2) the necrophiles (predators and parasites of necrophagous arthropods); (3) the omnivores (Hymenoptera); (4) the opportunists (Diptera, Collembola, Arachnids).

The coleopterans collected around the leatherback carcass had varied diets. Carabids, staphylinids and histerids are mainly predatory, while scarabeids are coprophagous and detritivorous. Tenebrionids are more eclectic, sometimes saprophagous, sometimes mycetophagous. We may suppose that members of the first three families prey on fly larva, hence their arrival occurs after development of their prey. The scarabeids feed on dead organic matter, contributing to the decomposition of the turtle carcass. The tenebrionids would play an intermediate role, sometimes acting as predators, other times saprophagous.

This hypothesis is reinforced by the variety of species collected, which illustrates the morphological heterogeneity related to the heterogeneity of the lifestyles specific to each family. And so the role of each insect family in the decomposition of the turtle carcass becomes clear. Each intervenes at the right moment depending on its possibilities and needs, its feeding habits and reproduction.

An entire series of organisms (including micro-organisms such as bacteria, mushrooms, and protozoa) are attracted to animal carcasses, including that of man (Leclerc and Verstraeten, 1992; Hewadikaram and Goff, 1991). When colonizing a carcass, the different species and their populations are subject to the laws of competition (Smith, 1986) and food and vital space are the primary factors of competition in larval stages. According to Leclerc (1978), necrophagous arthropods are selectively attracted to a carcass by the odors released over the course of decay. After thriving a certain time, a succession of insects finds the change of conditions in the substrate unfavorable, and is progressively replaced by the following.

The complex entomological successions that influence the rate of decomposition (Leclerc and Verstaeten, 1993) have been well identified in human legal medicine (forensic science), where their study allows for fairly accurate determination of the time elapsed since death. We can, therefore, suppose that by pursuing entomological study of sea turtle carcasses we may be able to identify the date at which a female was killed by poachers on the beach, or the beaching of a specimen whose death resulted from pollutants or fishing equipment.

A complex entomological fauna arrives by successive groups depending on the progressive changes in the substrate, thereby influencing the rate of decomposition of the carcass until complete mineralization (Leclerc and Verstraeten, 1993). Recycling is complete. The massive leatherback carcass appears a veritable ecosystem, itself only a time~/space subunit of the beach ecosystem (e.g., bullfrogs, Bufo marinus, feed the necrophagous insects).

Acknowledgements: We thank Letitia Farris Toussaint for the English translation.

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JACQUES FRETEY and REGIS BABIN, Federation française des Societes de Sciences naturelles, Museum national d'Histoire naturelle, Paris cedex 05, 75231 FRANCE; e-mail: fretey@ccr.jussieu.fr