Effects of temperature on the irritability caused by DDT and DDT-analogues in anopheline mosquitos

The author reports a series of investigations into the effects of temperature on irritability, caused by DDT or its analogues methoxychlor and DDD, in Anopheles labranchiae atroparvus and An. gambiae, species B; into the irritability of three other anophelines upon exposure to deposits of water-dispersible DDT powder; and into the relation between aging and DDT-irritation in anophelines. Irritability was measured by both the number of take-offs and the duration of flight over a 20-minute period at temperatures of from 19 degrees C to 32 degrees C.The flight activity of An. 1. atroparvus and An. gambiae B increased with increasing temperature to a peak at 23 degrees C for the former and 27 degrees C for the latter; it then fell with further increase in temperature to 32 degrees C.Over 20 minutes, the DDT-resistant An. pharoensis was less irritated than either An. gambiae A or An. punctulatus farauti (both susceptible) but over 30 minutes was more so than An. p. farauti.Among other findings were that methoxychlor and DDD were stronger irritants than DDT and that irritability declined with increasing age of the mosquitos.