Günther Nentwig

Use of repellents as prophylactic agents.

Abstract. Many biting insects are able to transmit diseases or are a regarded as pests. The use of repellents is one personal protection measure to avoid to been bitten. The first components which were used for this purpose were of plant origin. Some are still used, e.g., citronella oil. Systematic evaluation of synthetic repellents began during the Second World War. The most important compound resulting from these efforts is Deet, followed by less important ones such as dimethylphthalate or ethyl hexane diol. Compounds of more recent research are MERCK 3535 (aminopropionic acid ethylester), p-menthane-3,8 diol, CIC 4 (a lacton) and the piperidine derivatives AI3-37220 and Bayrepel (Icaridin). An overview of the toxicity and efficacy is given. A chance to improve the cosmetic properties and long duration efficacy is the development of new formulations. Applications other than the dermal one are the use of repellents as slow release formulations to achieve a long range effect and the development of systemic compounds, which are taken orally. To date, neither strategy has led to successful solutions.

Aggregation Agents in German Cockroach Blattella germanica: Examination of Efficacy

Aggregation behavior and reduced locomotory activity in the German cockroach is known to be caused by chemical compounds in the feces. The attractive and/or arrestant efficacy of three relevant substances was tested in first instars by a two-choice aggregation test and in adults with a locomotion compensator apparatus that allows quantification of taste-directed orientation and walking speed as a function of antennal stimulation. The three substances tested were a feces crude extract; a mixture of six carboxylic acids (mix G) out of a total of 29 that were identified in the feces extract and tested as single compounds and in various combinations; and a steroid glucoside denoted as blattellastanoside A, which has been suggested as an aggregation arrestant pheromone in Blattella germanica. With both of our test methods, feces extract and mix G proved to be very attractive, whereas the effects of blattellastanoside A were, if anything, very poor. Possible reasons for discrepancies are discussed.