CH. XVI.] DIPTEROUS INSECTS. 243 



for a knowledge of their remarkable mode of trans- 

 formation. The female deposites a single egg-like 

 mass, almost as large as her own body, and from 

 this the perfect fly shortly afterward bursts forth, 

 without undergoing any other transformations. 

 When first deposited, this egg is of a milky-white 

 colour, with a large, black, shining patch at one 

 end ; it is rather circular in form, and somewhat 

 flattened at the sides, with a semicircular impres- 

 sion at the end where the black spot is perceived, 

 which impression corresponds with the notch at 

 the extremity of the abdomen of the parent fly. 

 At first this egg is soft, except the black patch ; but 

 in the course of a day or two it acquires a suffi- 

 cient hardness to resist any ordinary pressure, and. 

 the whole assumes a blackish colour. It is about 

 one sixth of an inch long in the longest part, and 

 somewhat less when measured across, thus nearly 

 equalling the size of the body of the parent, and 

 rendering it difficult to conceive how the insect can 

 deposite so large a body. The abdomen of the hip- 

 pobosca, however, rather resembles a bladder than 

 a scaly covering, and is consequently capable of 

 great distention ; the egg, also, is not of so large a 

 size when first deposited as it acquires shortly 

 afterward : it is endowed with a slight motion, and 

 each side is furnished with a row of spiracular 

 points. 



In these insects, therefore, nature appears to quit 

 those paths by which she leads the majority of the 

 insect tribes to their perfect state ; since here, in- 

 stead of the regular gradation of egg, larva, pupa, 

 and imago, we find only one state, which, from 

 analogy, we might be tempted to believe was 

 that of the egg, from the circumstance of its being 

 deposited by the female. When, however, we find 

 the perfect fly bursting from it at once, we are com- 

 pelled to regard it as the pupa ; as we know, how- 

 ever, that it is during the larva state that all insects 



