DIPTERA. 409 



merited with yellow triangles or crescents on each side of the back, 

 and their antennae are somewhat like those of Midas and of the 

 gad-flies ; others (Sargus) are slender, often of a brilliant brassy 

 green color, with a bristle on the tip of their antennae. The 

 maggots of the latter live in rich mould. 



The Syrphians (Syrphidjs) have a fleshy, large-lipped pro- 

 boscis, elbowed near the base, and enclosing only four slender 

 bristles. They live on the honey of flowers. The last joint of 

 their short antennas bears a bristle, which is sometimes feathered. 

 Their heads are large and hemispherical. Many of these flies are 

 often mistaken for bees or wasps, and some of them lay their 

 eggs in the nests of the insects they so closely resemble. Others 

 drop their eggs among plant-lice, which their young afterwards 

 destroy in great numbers. The larvae of a few are aquatic, and 

 are provided with very long, tubular tails, through which they 

 breathe, and have been called rat-tailed maggots. Some of the 

 largest and most beautiful of these flies live, in the maggot state, 

 in rotten wood. One of these rat-tailed flies is often seen on 

 windows, in the autumn. It flies with a buzzing noise. Its eyes 

 are very large, and of a bright copper-color ; its body is brassy 

 green; and there are five gray stripes on the thorax. It meas- 

 ures about four tenths of an inch in length. It is the Eristalis 

 sincerus of my "Catalogue." The Milesia excentrica, named in 

 the same work, strikingly resembles a hornet ; its hind-body be- 

 ing banded with black and yellow in the same way. Its head and 

 thorax are black, the former margined around the eyes, and the 

 latter spotted, with yellowish-white. The legs are ochre-yellow, 

 except the shanks and feet of the first pair, which are black. Its 

 body measures nearly three quarters of an inch in length. My 

 Sphecomyia undata has the slender form of a Sjjhex or mud-wasp. 

 It is of a light brown color, darker on the back, and on the middle 

 of the thighs and shanks ; its head is conical, and bears the an- 

 tennae on the tip of the cone ; its wings are brown on the outer 

 part, with a small transparent spot near the edge, and the inner 

 part is transparent in two large wavy spaces. It is about five 

 eighths of an inch long, and its wings expand one inch and a quar- 

 ter, or more. It is possible that this singular fly may be the 

 Pyrgota undata of Wiedemann. An insect, closely resembling 



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