Swarming. 



regard to these insects. A rossi exhibited the phenomenon in the 

 greatest degree. In July, larvsa of this species were practically 

 never seen, and even for some time after the onset of the rains its 

 larva? were never found in the numerous pools then formed. By 

 the third week after the commencement of the rains its larvaa were 

 present in many pools, and by the sixth week they were very 

 abundant. By the middle of September larvae of this species were 

 present in enormous numbers in all the pools round the bazaars and 

 in most of the pools throughout the whole country-side. The adult 

 insects showed a corresponding increase, and though found with the 

 greatest difficulty before the onset of the rains they were present 

 in immense numbers in every bazaar and village in the neighbour- 

 hood a few weeks later. In spite of the fact that a reduction in 

 breeding places occurred at the end of September, they remained in 

 large numbers until the end of October and then rapidly disappeared. 



THE CHARACTERISTIC POSITION ASSUMED BY ANOPHELES WHEN RESTING 



ON ANY SURFACE. 



Many mosquitoes can be immediately recognised as " anopheles" 

 by the characteristic position which they assume when resting on a 

 wall or roof. From a short distance they look somewhat like 

 thorns projecting from the surface (PL III, 5, 6). The reason why 

 "anopheles" rest in such a characteristic position would seem to be 

 that the proboscis, head, thorax and abdomen of a mosquito of this 

 kind lie in one straight line, so that when the proboscis is directed 

 towards any surface, the abdomen is directed away from that surface. 

 The angle formed between an anopheles and the wall on which it 

 is resting differs with different species, and with practice it is often 

 possible to name a species by merely observing the angle which 

 it forms with the wall. A. rossi, for example, rests at an angle 

 of about 45 with the wall, while A fuliginosus forms very nearly a 

 right angle with it. Culicifacies, aitkeni and culiciformis lie almost, 

 if not quite, parallel to the surface on which they are resting, 

 and Annett and Dutton have shown that in a state of hibernation 

 macutipennis does not form an angle with the surface upon which 

 it is resting, but lies with its whole body nearly touching the 

 wall. It will be noticed, however, that the proboscis, head, and 

 body of an " anopheles," in whatever position it is resting, are always 



56] 



