DIPTERA. 



55 



genus Sciara, which in North America is said to appear when yellow fever is 

 prevalent. But perhaps the most notorious species is the so-called army-worm fly 

 (Sciara militaris), which has long attracted attention on account of the peculiar 

 habits of the larvae. This fly is completely black, with the exception of its legs, 

 which are brownish. The female, which is represented of the natural size at d, in 

 the accompanying illustration, and enlarged at c, is larger than the male, and has 

 the abdomen terminating in a pointed stylet. In the male, on the contrary, there 

 is at the apex of the abdomen a pair of thick two-jointed claspers, and between 

 these a couple of small adjacent processes, as shown at e. The extremely small 

 eggs are laid by the mother, to the number of about one hundred, upon soil amongst 

 fallen leaves on which the larvae feed. On attaining maturity, these larvse measure 

 nearly a quarter of an inch long, and have the form represented at a. The 

 black head is distinct, and furnished with eyes, and the semi-transparent body 

 consists of thirteen segments, some of which are furnished with lateral black 

 stigmata. In many countries of Europe where this insect is met with, vast hosts 

 of these maggots, forming a compact mass, sometimes several feet long and an inch 



ARMY-WORM FLY (Sciara militaris). 



., Larva ; b, Pupa ; c, Female midge ; d, The same (nat. size) ; e, End of abdomen of male ; /, A portion 

 of the antennae. (Magnified, except d.) 



or two broad, have been seen at times creeping along at a slow pace through the 

 woods like a greyish serpent. The maggots crawl along, not only side by side, 

 but also one over the other, all adhering together by their sticky surfaces, and con- 

 tinually changing their position in the column. At the close of their march, when 

 fatigue or want of nourishment causes them to rest for a time, the larvse composing 

 a single train collect into a ball, which gradually diminishes in size, and finally 

 disappears by the burrowing into the mould of those that are lowest in the mass. 

 For a long while the reason for this peculiar habit remained wrapt in obscurity, 

 and perhaps even yet we do not understand its full significance. It has been 

 suggested, however, that when the supply of food for the multitude runs short, the 

 whole army is moved by a sudden impulse to start in search of fresh supplies. It 

 is almost superfluous to add that the peasantry of the countries where this strange 

 phenomenon is observable, failing to understand its true significance, have from 

 time immemorial regarded it as something supernatural, and as foretelling various 

 events in the future, some looking upon it as a sign of the imminence of war, others 

 of the destruction of their crops, and so forth. The pupa of the army- worm is 



