THE STRAIGHT-SEAMED FLIES 



3017 



Fungus 

 Midges 



quent damp situations, are all of small size, and mostly pale in color. 

 To this family belongs the so-called yellow fever fly, a species of the 

 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 (Stiara 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 among 

 fallen leaves on which the larvae feed. On attaining maturity, these larvae 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 semitransparent 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 mag- 

 gots, forming a compact mass, sometimes several feet long and an inch or two 



c 



ARMY WORM FLY (Sciara militaris). 



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



antennae. (Magnified, except d.) 



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

 like a grayish serpent. The maggots crawl along, not only side by side, but also 

 one over the other, all adhering together by their sticky surfaces, and continually 

 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 larvae composing a sin- 

 gle train collect into a ball, which gradually diminishes in size, and finally disap- 

 pears by the burrowing into the mold of those that are lowest in the mass. For a 

 long while the reason for this peculiar habit remained wrapt in obscurity, and per- 

 haps even yet we do not understand its full significance. In 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 phenome- 

 non is observable, failing to understand its true significance, have from time 



