Methods for assessing the density and survival of blood-sucking Diptera.

Abstract

In a review of the principles involved in sampling insect populations Morris (I 17) has described the process as a mixture of art, science, and drudgery. The drudgery is known to us all, the science lies in understanding the responses of insects to trapping devices and their movements into the sampling area, while the art comes from an appreciation of the variables inherent in every field situation. The sampling methods adopted for blood-sucking flies may also reflect the background and objec­ tives of the operators. Those concerned with pest species, for instance, often employ standard techniques on a large scale with the immediate aim of monitoring the efficiency of control measures. They are dependent on funds from local authorities and may be answerable to the community in which they live. On the other hand. those concerned with assessing a disease hazard usually have more long-term objec­ tives, and their funds may come from a central authority. They often work in considerable isolation and individual whims and preferences lead to a lack of stan­ dardization in the techniques employed. Muirhead-Thomson (119) has recently reappraised the diverse methods used for sampling vectors and emphasized the need for greater uniformity. His lead is to be welcomed but much remains to be done. In some branches of entomology the use of specific chemical attractants for trapping pest species is becoming increasingly common, and the list of available lures is growing rapidly (8). This trend is much less noticeable in the case of biting flies probably because warm-blooded animals themselves are such potent sources of attraction. Thus, regardless of whether the active components have been identified or not, the use of animals as baits has long been the basis of many sampling methods used in the assessment of populations. At the same time medical and veterinary entomologists have been looking more critically at the interaction of trapping de­ vices and host attractants and have been considering how such traps could be