THE TACHINADiE. 613 



Most insects are hatched from eggs which are laid by the 

 mother on the substances that are to serve for the food of 

 her young. Some flesh-flies produce their young ahve, or 

 already hatched, and drop them on the dead and putrefying 

 animal matter, which they are to consume and remove in 

 the shortest possible time. An exception from the usual 

 course among insects appears therefore to have been made 

 in favor of these viviparous flesh-flies, to enable their young 

 promptly to perform their appointed tasks. These insects 

 produce an immense number of young, as many as twenty 

 thousand having been observed by Reaumur in a single fly.* 

 Our lai-gest viviparous flesh-fly is the SarcopJiaga Georgina 

 of Wiedemann. It appears towards the end of June, and 

 continues till the middle of August, or perhaps later. Its 

 face is silvery white, and there is an oblong square black 

 spot between the eyes, which are copper-colored. The tho- 

 rax is light gray, with seven black stripes upon it. The 

 hind body is nearly conical, has the lustre of satin, and is 

 checkered with square spots of black and white, shifting or 

 interchanging their colors according to the light wherein 

 they are seen. The legs are black, and the hindmost pair 

 are very hairy in the males. The female is about half an 

 inch long ; the male is rather smaller. In the Sarcophagans, 

 or flesh-eaters, as the name implies, the bristles on the an- 

 tennae are feathered. 



The flies that abound in stables in August and September, 

 and sometimes enter houses on the approach of rain, might 

 be mistaken for house-flies, were it not for the severity of 

 their bites, which are often felt through our clothing, and 

 are generally followed by blood. Upon examination they 

 will be found to differ essentially from house-flies in their 

 proboscis, which is very long and slender, and projects hori- 

 zontally beyond the head. The bristles on their antennae 

 are feathered above. Cattle suffer sorely from the piercing 

 bites of these flies, and horses are sometimes so much tor- 



* M^moires, Vol. IV. p. 417. 



