MUSCID^. 



413 



lid, which opens when the fly makes its exit, and bears two 

 small slender tubercles which project upwards. The posterior 

 end bears two terminal spine-like tubercles similar to those on 

 the head, but projecting horizontally. The puparium is glassy 

 green, and the limbs of the enclosed pupa can be partially seen 

 through the skin. The rings are (especially on the thorax) 

 spinose, being the remnants of the rows of spines around the 

 hind edge of the larval segments. It is .15 of an inch long. 

 The pupa lies a short distance from the opening of its burrow, 

 which is about half an inch long, and is situated between the 

 wood and the bark. 

 The larva before pupa- 

 ting eats away the bark, 

 leaving a thin outer 

 scale, or roundish black 

 space Avhich can be 

 folded back like a lid, 

 which the fly pushes 

 open when it emerges. 

 Several swellings occur 

 on the twig in the space ^'s- 335- 



of six inches. The fly appeared the 25th of June. Dufour 

 states that in Europe Lonchcea nigra lives in the outer bark of 

 the oak, and another under the bark of the poplar, while still 

 another species makes a sort of gall in the dogsgrass. 



The genus Sphyracephala is remarkable for its stalked eyes, 

 which are placed on long stems going out from the sides of 

 the head. Some species are found fossil in the Prussian 

 amber. S. brevicornis Say is rather rare. 



The Cheese maggot is the larva of Pio^Mla casei (Fig. 335) 

 a shining black fly, three-twentieths of an inch long, with the 

 four posterior legs yellowish, and with transparent wings. 

 The whitish larva is cylindrical, and .22 of an inch in length, 

 and is acutely pointed towards the head and truncated behind, 

 with two long horny stigmata in the middle of the truncature, 

 and two longer fleshy filaments on the lower edge. When 

 moving it extends its mouth-hooks, and pulls itself along by 

 them. Mr. F. W. Putnam has called my attention to the 

 power of leaping possessed by the maggot. When about to 



