Thermal effect of blood feeding in the telmophagous fly Glossina morsitans morsitans.

During feeding on warm-blooded hosts, haematophagous insects are exposed to thermal stress due to the ingestion of a meal which temperature may highly exceed their own body temperature. In order to avoid overheating and its subsequent deleterious effects, these insects respond by setting up molecular protective mechanisms such as heat shock proteins synthesis or by using thermoregulative strategies. Moreover, the duration of contact with the host depends on the way of feeding displayed by the different species (either telmophagous or solenophagous) and thus also impacts their exposure to heat. Solenophagous insects feed directly on blood vessels and are relatively slow feeders while telmophagous insects by lacerating capillaries, facilitate their access to blood and thus feed more quickly. The aim of this work was to investigate to what extent strictly telmophagous insects such as tsetse flies are exposed to thermal stress during feeding and consequently to evaluate the impact of the feeding strategy on the exposition to overheating in haematophagous insects in general. Real time thermographic analysis during feeding revealed that the flies' body significantly heat up quite homogeneously. At the end of feeding, however, a marked regional heterothermy occurs as a consequence of the alary muscles warm up that precedes take-off. Feeding strategies, either solenophagy or telmophagy, thus appear to have a great impact on both exposition to predation risks and to thermal stress.