MOSQUITOES 467 



others believed that some irritating fluid is injected by the Mos- 

 quito when it bites. But why should it want to irritate as well 

 as to bite ? Macloskie, considering that the Mosquito is really 

 a. feeder on plant-substances, suggests that the fluid injected may 

 be for the purpose of preventing coagulation of tlie plant-juices 

 during the process of suction. It is a rule that only the female 

 Mosquito bites, the male being an inoffensive creature, and pro- 

 vided with less effectual mouth-organs; it has, however, been 

 stated by various authors that male Mosquitoes do occasionally 

 bite. It is difficult to understand the blood-sucking propensities 

 of these Insects ; we have already stated that it is only the 

 females that suck blood. There is reason to suppose that it is an 

 acquired habit ; and it would appear that the food so obtained 

 is not essential to their existence. It has indeed been asserted 

 that the act is frequently attended with fatal consequences to 

 the individual that does it. The proper method of mitigating 

 their nuisance is to examine the stagnant waters in localities 

 where they occur, and deal with them so as to destroy the larvae. 

 These little creatures are remarkable from the heads and thorax 

 being larger and more distinct than in other Dipterous larvae. 

 Their metamorphoses have been frequently described, and recently 

 the numerous interesting points connected with their life-histories 

 have been admirably portrayed by Professor Miall,^ in an accessible 

 form, so that it is unnecessary for us to deal with them. 

 Corethra is placed in Culicidae, but the larva differs totally from 

 that of Culex ; it is predaceous in habits, is very transparent, has 

 only an imperfect tracheal system, without spiracles, and has two 

 pairs of air-sacs (perhaps we should rather say pigmented struc- 

 tures possibly for aerostatic purposes, but not suppliers of oxygen). 

 The kungu cake mentioned by Livingstone as used on Lake 

 Nyassa is made from an Insect which occurs in profusion there, 

 and is compressed into biscuit form. It is believed to be a 

 Corethra. One of the peculiarities of this family is the pre- 

 valence of scales on various parts of the body, and even on the 

 wings : the scales are essentially similar to those of Lepidoptera. 

 Though Mosquitoes are generally obscure plain Insects, there 

 are some — in the South American genus Megarrhina — that are 

 elegant, beautifully adorned creatures. Swarms of various species 

 of Culicidae, consisting sometimes of almost incalculable numbers 

 ^ Natural Histury of Aqiuttk Insects, London, 189;), cliap. ii. 



