Fungus Gnats 



snails and construct delicate cocoons. It was formerly supposed 

 that with some of the species the larvae formed galls on leaves, 

 as, for example, one species was supposed to belong to the genus 

 Sciara which makes the beautiful crimson, eye-like spots often 

 seen on the leaves of the silver maple, but the larvae in these spots 

 are now thought to be Cecidomyian and it is doubted whether 

 any true Mycetophilids ever make galls. Some of the Sciaras also 

 have the curious habit when in the larval state of traveling in 

 great armies so close to each other as to almost form one mass. 

 They have then been called worm-snakes. They travel in a 

 solid column several deep over each other at the rate of about an 

 inch a minute. In Europe they have from this habit been called 

 the army-worm, but in this country the term army-worm is 

 applied to a caterpillar. One of our American species of this 

 habit has been reared by Pratt and proves to be Sciara fraterna. 

 Some species live in the sap of trees, and injury to the bark of a 

 maple or an elm causing the sap to flow in the spring frequently 

 attracts these little midges, which will lay their eggs there and 

 subsequently little maggots will be found. One species, known 

 as Epidapus scabiei, is said by Hopkins to be the cause, or at 

 least the transmitter, of the disease known as scab among 

 potatoes. He also finds that the same insect will breed in 

 healthy potatoes. The use of scabby seed potatoes offers favor- 

 able conditions for the attack of these insects as these are attracted 

 to the scabby spots under which they breed and are thus brought 

 into contact with the growing tubers. Another species feeds 

 upon ripe apples. One of the Sciaras has been called the yellow- 

 fever fly in the southern United States, since it made its appear- 

 ance in extraordinary numbers during a yellow fever epidemic. 

 It has, however, no connection with the disease. Certain of 

 these fungus gnats jump actively as well as fly. Sciara iritici 

 Coq., figured herewith, in its larval stage damages young growing 

 wheat plants. 



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