FLEAS. 219 



Family II. — Cecidomyiidce. 



Small delicate species, clothed with long hair ; antennae more 

 or less moniliform, with a few hairs ; generally comjjosed of twenty- 

 four joints in the males, and from twelve to fourteen in the 

 females ; wings horizontal, with but few nervures ; vegetable 

 feeders. 



The species of this family are often called Gall Gnats. They 

 attack various plants, especially wheat and willow, generally more 

 or less distorting or stunting the plant, even when they do not 

 produce one of the abnormal excrescences to which the name gall 

 would be strictly applicable ; some species, too, attack rotten wood 

 The best known and most mischievous species, however, are per 

 haps the Wheat Midge (Dijjlosis Tritici, Kirb.), and the Hessian Flj- 

 (Cecidomyia Destructor, Say). The former is a small yellow fly, 

 with a long telescope-like ovipositor, with which it lays its eggs in 

 the blossom of the wheat. These hatch into small maggots, which 

 become yellow with age, and render the plant abortive by devour- 

 ing the pollen. 



The Hessian Fly derives its name from its having been intro- 

 duced into the United States (as was supposed) by the Hessian 

 troops during the War of Independence. It is, however, still a 

 much-disputed point among entomologists as to whether this story 

 of its origin is correct, for it is thought to be an indigenous Ameri- 

 can species, and distinct from the various allied European forms 

 which some suppose to be the same. So excellent an authority as 

 Dr. Packard is, however, thoroughly convinced of its European 

 origin. It is a brown fly, which lays its eggs on the leaves of the 

 wheat, and the maggots, when hatched, creep down to the base of 

 the sheath, where they feed upon the sap, and, if numerous, soon 

 destroy the stalk. These maggots are at first semi-transparent, 

 but gradually darken with age, and, when full-grown, resemble so 

 many flax seeds imbedded in the substance of the stalk. 



For more than a century this insect has proved exceedingly 

 destructive to wheat in America, but is somewhat uncertain in 

 appearance and locality, not proving itself equally abundant and 

 destructive in the same district at all times. 



Before dismissing the Cecidomyiidce it must be mentioned that 

 a few species are dimorphous, or rather exhibit alternation of gene- 

 rations, certain larvae actually bringing forth living larvae, a mode 

 of reproduction somewhat resembling that observed in Aphidce. 



