ON THE LIFE HISTOEY OF UGIMYA. 33 



space of time, is that of coloration, and the increase of hair : thus the 

 color of the pupa changes gradually from light to grayish brown, and 

 then to grayish black slightly tinged with yellow, the compound eyes 

 become deep ochre-red, and the hairs on the body grow thickly all 

 over its surface. 



The pupa when lodged under ground is liable to die from two 

 causes, ( 1) from the unfavorable condition of the earth in which it rests, 

 and (2) from the ravages of a parasitic mite : — 1st. When the earth 

 keeps moist and unexposed to the sun-light, the pupa may remain 

 alive and undergo its complete development ; but if on the contrary 

 the earth becomes dry or is exposed to the direct rays of the sun, the 

 pupa will die in a longer or shorter period. 2nd. The mite which in- 

 fects the pupa is probably a species of Tyroglyphus (P/. VI, ßg. 10). 

 The body which is about 0.45 mm. in length, is oval in shape, faint 

 yellow in color, and covered with a few long colorless bristles. There 

 are four pairs of long jointed legs, of which each is composed of five 

 segments, and ends with a single hooked claw. The male and female 

 are similarly colored, but differ slightly in size. The eggs (PL VI, ßg. 

 IT) are oval in shape and very small, being only 0.13 mm. in the long- 

 est diameter. The egg-shells are hard and chitinous, and their surface 

 is decorated with scattered masses of granules. When the young is in 

 the process of hatching out, the one pole of the egg opens by a valve, 

 through which it soon emeeges. Sometimes these parasites increase 

 enormously in number, so that the interior of the puparium is filled up 

 with hundreds of them instead of with the pupa of the fly. 



About the middle part of April of the following year, the perfect 

 fly begins to appear above ground, and continues to come out during 

 the following three weeks. As I have mentioned before, the pupa 

 remains at the depth of 2-3 inches or even more beneath the ground. 

 The manner in which the perfect fly hatches out from a puparium is 



