Dirofilaria aethiops Webber, 1955, a filarial parasite of monkeys III. The larval development in mosquitoes

Extract

1. A description is given of the morphological development of the larval stages of Dirofilaria aethiops in the mosquito Aëdes aegypti.

2. The first-stage larvae migrate from the stomach to the connective tissue in all parts of the mosquito body, where they pass through the inactive ‘sausage’ stages. At 26° C. and 80% relative humidity the first moult takes place about the twelfth day of development and the second moult about the sixteenth day. The third-stage larvae migrate towards the proboscis where they can be found after 18–20 days.

3. The number of microfilariae ingested by the mosquito is approximately equal to the number which would be expected from the numbers in the blood of the monkey and the volume of the blood meal. The death rate of the larvae in the mosquitoes is very high for the first 2 days, but less severe later. Approximately 1% of the ingested microfilariae survive 20 days; at this time two-thirds of the surviving larvae have reached the third stage.

4. Comparison of D. aethiops with other filariae shows that first-stage larvae of different species can often be distinguished by the structure of the tail, which is the same as that of the microfilaria. Second-stage larvae are similar to each other in morphology but develop in characteristic sites in the host. Third-stage larvae differ from each other in the cephalic and caudal papillae.