Wetenschap - 6 maart 1997

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Death, destruction and entomology
We don't usually think of flies, bees and mites as our best friends. Although they have proven their usefulness in nature, wed rather not have them in our houses. But who would have thought that insects can also play a crucial role both in solving as well as in committing murders? In the series of lectures Insects and Society, the Department of Entomology dedicated one evening to the macabre role of deadly normal insects
A classic case of a murder solved by an entomologist is the story of a Hungarian ferryman. A corpse was found on the ferry when the ferryman concerned was on duty. Although he denied any involvement with the murder, he was arrested as the prime suspect and put behind bars. Eight years later an entomologist looked into the case and read the coroner's report. This mentioned the presence of blow flies on the corpse at the time the corpse was discovered. However, this type of green blow fly only lays its eggs in full sunlight. The day of the crime, the ferrymen did not come on duty until 6 pm, after sunset. The killing, however, must have taken place before 6 pm, and therefore before the ferrymen's arrival on the ferry. Thus, after all those years his innocence was proven and the ferrymen released. Last Wednesday 26 February, Jan Krikken, a modern Sherlock Holmes, told the audience about the role insects can play in solving cases of murder. Krikken is scientific director of the Dutch National Museum of Natural History and part-time forensic entomologist. A corpse can become infested by blow flies just a few minutes after death, and at a later stage other types of flies and beetles start to arrive. Corpses are in fact micro-biotopes, states Krikken
Dry decay
According to the entomologist, crucial factors for determining the postmortem interval (PMI) include the kind of insect present, and whether eggs, larvae or pupae are found. Blow fly eggs will be found on the corpse during the first 15 hours after arrival of the blow flies. If blow fly larvae are found it means that the person has been dead for at least 17 hours. However, the presence of other insects may also provide useful information. Ants and beetles may appear because they eat blow fly eggs. After two weeks beetle larvae will be found, and mites and moths will start to arrive on the scene as well. After three weeks - by then the corpse is already in the stage of dry decay and only skin and bones remain - caterpillars start creeping onto the scene of the crime
Geographical and climatological conditions during the PMI and at the time of the murder constitute a third important set of factors. If you find a species of maggots which prefers a sunny environment on a corpse which is discovered indoors, this might be an indication that the corpse has been moved. On the other hand fauna underneath a corpse dies fast and only recovers slowly. Where a corpse has been dragged away from the scene of the crime it is possible to use this kind of evidence to trace the original spot
Krikken sums up case after case as if he is solving crosswords. He attributes his liking for the taxonomy of creepy crawlies animals to the fact that he is married to a municipal coroner. He admits however, that not all cases he works on are that spectacular and it is not always a question of murder: Insects in confiscated drugs can tell you more about the origin of the drugs
Aphrodisiacs
Although forensic entomology is quite a rare profession, the significance of this field has been recognized for a long time. As early as 1235 A.D. Sung Tzu, a Chinese death investigator, described a case. A murder by slashing had been committed in a Chinese village. When the usual methods of questioning proved unsuccessful, the death investigator asked all the villagers to bring their sickles and lay them out before the crowd. Flies were attracted to the tissue remains stuck to one of the sickles. The owner of the sickle subsequently confessed
These substances, which attract poisonous insects, are the specialization of the evening's second speaker, Professor Murray Blum of the University of Georgia, USA. Blum discloses that poisonous insects not only constitute health hazards for humans, but the substances they produce can also be manipulated to become dangerous intoxicative agents. An historic example is Spanish fly, which is produced by blister beetles. Spanish fly is an aphrodisiac, which means that it heightens sexual desire. Marquis de Sade used to give prostitutes pastilles with high concentrations of this substance, often with fatal consequences for his victims. In isolated cases this practice still occurs. Blum adds that toxicity is, of course, dosage dependent
Death caused by swarming African honey bees is a real possibility and the risk is higher than being killed by a snake bite in the USA. Blum argues that Africanized bees can be guided to a source by using attractant pheromones. Synthetic equivalents are commercially available, but, For some insects bananas or blue cheese work just as well, says Blum
MSc students want more time for thesis
Thesis supervisors should be available throughout November, December and January. Since most teachers are on holiday during the period when you most need their advice and supervision, January is not a good month to finish your thesis or study. Moreover, the period of time allocated for the thesis should be extended, preferably by four or five months. This is one the most striking results of the annual MSc evaluation workshop. Each year, the Dean's Office and facilitators of the Department of Agricultural Education invite recently graduated students to evaluate their stay and study in Wageningen and to pass on the results to the relevant departments
The length of programmes is a yearly recurring theme, even though this year almost 60% of the international students did manage to graduate within the fixed period, says Martha Bloemberg, chair of the platform of programme directors. She feels that this evaluation is a good indicator of the general mood among students. But it is difficult to evaluate some of the results if you do not know the specific background to the remarks made. We also organise an evaluation of the MAKS programme. Since many remarks concern individual students or specific aspects of courses it is easier to take concrete action at programme level.
The workshop results concerning student housing seem to support Bloemberg's opinion. For instance, placing just one international student on a corridor is not a good policy. It would be better to establish either international corridors or corridors which are half Dutch and half international. Nevertheless, over half of the workshop participants reported having lived on a nice corridor with nice people
African specialities' shop opens its doors

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