SIPHONAPTERA 161 



of winter wheat; the burning or plowing of stubble; the early planting of 

 strips of decoy wheat to attract the egg-laying females to deposit their eggs, 

 and then to be burned; and the rotation of crops.' 



Another common and conspicuous gall-gnat is the pine-cone-willow gall- 

 gnat, which lays its eggs in the newly formed buds of the willow. The 

 stem ceases to grow, but the leaves continue, causing the bud to resemble a 

 pine-cone. In this the larva remains through the summer and winter, 

 pupating in early spring, soon after which the adult emerges. There are a 

 number of others, as the clover-leaf midge, the clover-seed midge, and the 

 wheat midge, each injurious to its respective crop. 



The Syrphus flies (Syr'phidoe), of which there are twenty-five hundred 

 species, differ much. Some species in the adult form imitate bees and 

 wasps (Fig. 132). They can be distinguished by the longitudinal " spu- 

 r'ous " vein between veins three and five. Some of the larvae are found in 

 ants' nests and some in the nests of bumble-bees and wasps. One of the 

 commonest is the yellow-banded species of the genus Syrphus, whose larvae 

 do great good by destroying aphids, in whose colonies they live. 



The larvae of one of the bee-flies (Bomhyli'idce) are also friends of man. 

 They destroy many grasshoppers by burrowing into the egg-cases and 

 devouring the eggs. The adults of these maggot-like larvae are swift, 

 hairy, and bee-like, mimicking the bee in appearance and feeding habits. 



ORDER X. SIPHONAP'TERA 



The fleas consist of a single family, the PuUc'idce, of nearly- 

 one hundred and fifty species, about fifty of which are found in 

 the United States. Until recently the fleas were regarded as 

 degenerate wingless Diptera, but entomologists now place 

 them in a separate order. They are found usually as temporary 

 external parasites on the cat, rat, rabbit, dog, poultry, and 

 man. 



The mouth parts are adapted for piercing and sucking. 

 They are almost wingless, the wings being represented by mere 

 scaly plates. The bodies are naked, smooth, hard, oval, and 

 compressed. The metamorphosis is complete (Fig. 133). 

 The " small, slender, white, footless, worm-like grubs " are 

 composed of thirteen segments. They seem to live on dry dust 

 and the organic matter it contains. When grown they usually 

 spin a silken cocoon and pupate in the dust. In the species 

 infesting cats and dogs the larval life lasts only about a week. 

 The development from the egg to the adult requires but two 

 weeks. Fresh pyrethrum dusted about the rugs where dogs 

 and cats lie, or spraying the rugs with formalin, will help get 

 rid of fleas. 



' Jackson and Daughterty's " Agriculture through the Laboratory and 

 School Garden." 



a 



