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.     

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.     

Diversity of Forensic Rove Beetles (Coleoptera,Staphylinidae) Associated with Decaying Pig Carcass in a Forest Biotope

Most forensic studies are focused on Diptera pattern colonization while neglecting Coleoptera succession. So far, little information is available on the postmortem colonization by beetles and the decomposition process they initiate under temperate biogeoclimatic countries. These beetles have, however, been referred to as being part of the entomofaunal colonization of a dead body. Forensic entomologists need increased databases detailing the distribution, ecology, and phenology of necrophagous insects, including staphylinids (Coleoptera, Staphylinidae). While pig carcasses are commonly used in forensic entomology studies to surrogate human decomposition and to investigate the entomofaunal succession, very few works have been conducted in Europe on large carcasses. Our work reports the monitoring of the presence of adult rove beetles (Coleoptera, Staphylinidae) on decaying pig carcasses in a forest biotope during four seasons (spring, summer, fall, and winter). A total of 23 genera comprising 60 species of rove beetles were collected from pig carcasses.     

Responses of Lucilia sericata Meigen (Diptera: Calliphoridae) to cadaveric volatile organic compounds

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.     

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.     

Volatile organic compounds released by blowfly larvae and pupae: new perspectives in forensic entomology

To evaluate postmortem intervals (PMIs), one should take into account the determined age of necrophagous flies present on the cadaver. However, PMI determination needs further improvement, and rapid and accurate approaches have therefore to be developed. While previous studies have focussed on insect cuticular hydrocarbons, here we explore the volatile profile released by larvae and pupae of Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae). We monitored changes in volatile compounds daily, by headspace solid-phase microextraction, followed by gas chromatography-mass spectrometry. Branched and unbranched hydrocarbons, alcohols, esters and acids were identified, and the volatile profile was shown to vary, in both composition and quantity, with the age of the larva/pupa under investigation. We concluded, based on the analysis of the released volatile organic compounds, that it is possible to increase the accuracy of the estimated PMI, through improved estimation of the age of blowflies present on the cadaver.     

Copycatting the smell of death: Deciphering the role of cadaveric scent components used by detection dogs to locate human remains

Human remains detection dogs (HRDD) are commonly used by law enforcement agencies to search for cadavers. Biological material is typically used as a training stimulus, also called aids, to train dogs to recognize the smell of cadavers. While HRDD training approaches have received extensive attention, information remains limited on the olfactory cues used to train them. Here, we aimed to decipher the chemical basis of detection dog olfaction. Five specific objectives were explored to precise whether the composition or the concentration of the training aids drives the HRDDs responses. We recorded the behavioral responses of four HRDDs exposed to different cadaveric-like smells. We found that HRDDs recognized a simplified synthetic aid composed of cadaveric compounds. The lowest concentration at which HRDDs continued to perceive the cadaveric smell was determined. HRDDs were not impacted by slight modifications to the chemical composition of a blend of odors that they have been trained with. HRDDs associated sulfur and nitrogen compounds as human cadaver. Our findings highlight a lack of specificity of HRDDs to cadaveric compounds, which could lead to error of detection. Moreover, all dogs did not positively respond to the same blends, despite being trained with the same aids and procedure. However, we confirmed that dogs could be trained with a simplified blend of molecules. The chemical composition of a training aid has, therefore, high consequences on the performance of the trained animal, and this conclusion opens additional questions regarding olfaction-based detection animals.