FLIES. 



431 



The larvse are thick, cylindrical, somewhat flattened below, the segments with 

 transverse swellings for locomotion, either naked or with bands of fine, short bristles. 

 Almost all are parasitic, chiefly within the larvae of Lej)idoptera, but also frequently 

 those of Orthoptera, earwigs, beetles, some Hymenoptera, isopod crustaceans, and on 

 turtles. 



Of the numerous other sub-families, which are composed chiefly of small flies, only 

 a few can be mentioned here. With the exception of the Anthomyinse, they will be 

 distinguished from the preceding group — the Muscidae Calyptratse — by the absence 

 or rudimentary condition of the tegulae or membranous scales above the halteres. 

 They have hence been called Muscidse Acalyptratee. 



Most of the species live in excrement or decaying vegetable matter, but many are 

 leaf miners, others gall producers, etc. 



Very noticeable are many of the Ortalinse and Trypetinae, mostly small species with 

 beautifully marked wings. Many of their larvae live in fruits, and in the stems of 

 plants, producing galls, others are leaf miners. A common species is Strauzia longi- 

 pennis^ a yellow fly with wavy markings on the wings that ,will be seen about sun- 

 flowers, resting on the leaves with the wings outstretched and in gentle motion. 

 Camptoneura picta is another very common 

 species ; it has dark brown wings, with a trian- 

 gular transparent spot in front and another 

 behind. 



The larvae of Piophila casei, or cheese- 

 mites, are known to every one. The fly is 

 shining black, about four millimeters in length, 

 with transparent wings, and the four posterior 

 legs yellowish. "The whitish larva is cylin- 

 drical, about a fifth of an inch in length, and is 

 acutely pointed toward the head, and truncated 

 behind, and with two longer fleshy filaments on 

 the lower edge. When moving it extends its mouth-hooks and pulls itself along by 

 them." The power of leaping possessed by them has long been observed, whence 

 they are often called " skippers." " When about to leap, the larva brings the under 

 side of the abdomen towards the head, while lying on the side, and reaching forward 

 with the head, and at the same time extending its mouth-hooks, grapples by means of 



them with the hinder edge of the truncature, and 

 pulling hard suddenly withdraws them, jerking 

 itself to a distance of four or five inches." (Pack- 

 ard.) 



Other species of this genus have the singular 

 habit of living in wine, or even in strong alcohol, 

 in their earlier stages. 



Of more especial interest are species of Ephydra, 

 remarkable for their habit of living, often in fabu- 

 lous numbers, in marine or strongly alkaline waters. 

 An account given to the writer by Professor Brewer 

 concerning the habits and uses of E. californica is 

 of interest : — 

 " The waters of Lake Mono are clear, very heavy, have a nauseous taste, and, when 



Fig. 543. — Piophila casein cheese-fly, enlarged. 



Fig. 544. — Ephydra halopMla; a, Tring, 

 enlarged. 



