48 ARTHROPODA 



within its hardened brown skin. In the mean time trans- 

 formation to the adult fly occurs, and the skin is then rup- 

 tured for its exit. 



Howard says he has seen millions of the army worm at 

 work and not a single individual could be found which did 

 not bear Tachina eggs. One great outbreak of the army 

 worm hi Alabama in 1881 was completely frustrated by 



the Tachina flies and 

 a few other parasites. 

 Syrphus Flies. 

 These are found 

 among the flowers 

 and shrubbery in the 

 bright sunshine. 



FIG. 27. Syrphus flies. Photograph, natural size. ,, ,, ., 



They resemble the 



bees and the wasps, though many of them are as small as 

 the house fly, and are often marked with orange or yellow- 

 ish bands on the abdomen. The larvae of some species 

 may be found feeding on plant lice, while others live on 

 decaying wood and manure. At least one, the drone fly 

 (Eristalis tenax), breeds in decaying flesh, where its larva 

 is known as the rat-tailed maggot. The idea prevalent, 

 that carcasses of animals may generate swarms of bees, 

 arose from the fact that the drone fly closely resembles 

 the honey bee. The story of Samson in the Book of 

 Judges relates such an incident. 



Botflies. The several species of these are parasites 

 of vertebrates. The botfly of the horse (Gastrophilus equi) 

 is familiar to all who have been about horses in late summer 

 and noticed a large fly similar to a honey bee depositing 

 minute yellowish elongate eggs on the fore legs of the horse. 



