Christine Frederickx

Responses of Lucilia sericata Meigen (Diptera: Calliphoridae) to Cadaveric Volatile Organic Compounds*

Abstract:  Flies of the Calliphoridae Family are the most forensically important insects because of their abundance on the decedent during the first minutes following death. Necrophagous insects are attracted at a distance by a decomposing body, through the use of volatile chemical cues. We tested the possible attractive role of some volatile organic chemicals (VOCs) released by decaying cadavers, on male and female of Lucilia sericata Meigen (Diptera: Calliphoridae). Two complementary approaches were used. Electroantennography (EAG) allowed identifying the semiochemicals that are detected by the olfactory system of L. sericata. Dose–response tests with EAG showed that dimethyl disulfide (DMDS) and butan‐1‐ol elicited the highest responses. Behavioral assays showed that, among the VOCs tested, DMDS and butan‐1‐ol are attractive for L. sericata, while the other VOCs are repulsive or do not cause any behavior. Our results may have potential implications in a better understanding of attractiveness of blowflies toward a corpse.

Forensic Entomology Investigations From Doctor Marcel Leclercq (1924–2008): A Review of Cases From 1969 to 2005

ABSTRACT Dr. Marcel Leclercq was a pioneer in the field of forensic entomology. He has provided his knowledge of insect biology to many forensic cases, and most of them have found the way to publication. Most of the articles he has written were focused on individual cases, and despite the abundance of entomoforensic investigations he conducted, no synthesis has been published. This article summarizes 36 yr of forensic entomological investigations in temperate Europe, mainly in Belgium. Dr. Leclercqs work includes 132 entomological cases involving 141 human corpses found in various death scenes. Under certain conditions, insect specimens found at death scene can provide information on when (postmortem interval estimation), where and how a person died. More or less 100 insect species associated with a dead body have been identified by Dr. Leclercq.

Electrophysiological and Behavioral Responses of Thanatophilus sinuatus Fabricius (Coleoptera: Silphidae) to Selected Cadaveric Volatile Organic Compounds

Soon after death, carcasses release volatile chemicals that attract carrion insects including Silphidae. Nevertheless, it is not known which chemical cues are involved in the attractiveness of the carcass. So far, little information is available on the chemical ecology of carrion beetles, particularly concerning the subfamily of Silphinae. The biological role of selected cadaveric volatile organic compounds including dimethyldisulfide (DMDS), butan‐1‐ol, n‐butanoic acid, indole, phenol, p‐cresol, putrescine, and cadaverine on the silphine species, Thanatophilus sinuatus Fabricius, was investigated using both electrophysiological and behavioral techniques. Among the tested cadaveric compounds, butan‐1‐ol and DMDS elicited the strongest electroantennography (EAG) from both T. sinuatus male and female antennae. In a two‐arm olfactometer, males and females were significantly attracted to DMDS for both tested doses, whereas only males were attracted to p‐cresol at 100 ng. Putrescine was repellent to males at the dose of 1 μg.

Host-habitat location by the parasitoid, Nasonia vitripennis Walker (Hymenoptera: Pteromalidae).

This study investigated the role of odorant cues used during host‐habitat location by the generalist parasitoid, Nasonia vitripennis Walker. Nasonia vitripennis is a common parasitoid of Dipteran pupae found in association with decaying carrion. Behavioral assays were used to investigate the host‐habitat searching behavior under different scenarios. First, we demonstrated N. vitripennis to be significantly attracted toward odorant cues associated with decaying meat. The biological activity of nine of the volatile molecules constituting the odor of decaying meat was tested on the searching behavior of parasitoid females through two complementary chemoecological approaches: electroantennography (EAG) and olfactometry bioassays. Butanoic acid and butan‐1‐ol elicited high olfactory responses, but no attraction was induced by these two chemicals. Behavioral assays showed that, among the VOCs tested, methyldisulfanylmethane (DMDS) was the only volatile chemical to induce attraction in N. vitripennis.

The community of Hymenoptera parasitizing necrophagous Diptera in an urban biotope

Abstract Most reports published in the field of forensic entomology are focused on Diptera and neglect the Hymenoptera community. However, Hymenoptera are part of the entomofaunal colonization of a dead body. The use of Hymenoptera parasitoids in forensic entomology can be relevant to evaluate the time of death. Hymenoptera parasitoids of the larvae and pupae of flies may play an important role in the estimation of the post-mortem period because their time of attack is often restricted to a small, well-defined window of time in the development of the host insect. However, these parasitoids can interfere with the developmental times of colonizing Diptera, and therefore a better understanding of their ecology is needed. The work reported here monitored the presence of adult Hymenoptera parasitoids on decaying pig carcasses in an urban biotope during the summer season (from May to September). Six families and six species of parasitoids were recorded in the field: Aspilota fuscicornis Haliday (Braconidae), Alysia manducator Panzer, Nasonia vitripennis Walker (Pteromalidae), Tachinaephagus zealandicus Ashmead (Encyrtidae), Trichopria sp. (Diapriidae), and Figites sp. (Figitidae). In the laboratory, five species emerged from pupae collected in the field: Trichopria sp., Figites sp., A. manducator, N. vitripennis, and T. zealandicus. These five species colonize a broad spectrum of Diptera hosts, including those species associated with decomposing carcasses, namely those from the families Calliphoridae, Muscidae, Fanniidae, and Sarcophagidae.

Associative learning of Nasonia vitripennis Walker (Hymenoptera: Pteromalidae) to methyldisulfanylmethane

Traditional methods of volatile detection used by police typically consist of reliance on canine olfaction. However, dogs have some limitations such as cost of training and time of conditioning. The possibility of using parasitic wasps for detecting explosives and narcotics has been developed. Moreover, wasps are cheap to produce and can be conditioned with impressive speed for a specific chemical detection task. We examined the ability of Nasonia vitripennis Walker to learn and respond to methyldisulfanylmethane (DMDS), a volatile discriminator of cadaver. The training aimed to form an association between an unconditioned stimulus (pupae) and the conditioned stimulus (odor source). After the training, the time spent by conditioned wasps in the DMDS chamber was measured. Statistical analysis showed that the increasing concentrations involved an increase in the time spent in the chamber containing DMDS. This study indicates that N. vitripennis can respond to DMDS, which provide further support for its development as a biological sensor.

Depth and type of substrate influence the ability of Nasonia vitripennis to locate a host.

Abstract The foraging behaviour of a parasitoid insect species includes the host’s habitat and subsequent location of the host. Habitats substrate, substrate moisture, and light levels can affect the host searching of different species of parasitoids. However, the depth at which parasitoids concentrate their search effort is another important ecological characteristic and plays an important role in locating a host. Here, we investigated the ability of a pupal parasitoid, Nasonia vitripennis Walker (Hymenoptera: Pteromalidae), to penetrate and kill fly pupae located at different depths of the substrate. Three different types of substrate were tested: loam soil, compost, and vermiculite substrate. In both loam soil and compost, all of the parasitism activity was restricted to pupae placed directly on the surface. Parasitism activity in vermiculite showed that the average number of pupae parasitized decreased with depth of substrate. These results suggest that fly pupae situated deeper in the substrate are less subjected to parasitism by N. vitripennis .