304 APPLIED ENTOMOLOGY 



are found in all parts of the world. They differ greatly in their habits, 

 food, and general modes of life. Some are serious pests either of crops 

 or of man, while others are among the most beneficial insects known, 

 acting as parasites. A number of species function as carriers of disease- 

 producing organisms and are of importance in that way. 



About fifty families of Diptera are recognized, many of them very 

 large while others contain few species. 



Fig. 320. — Large Crane-fly (Tipulid), head bent downward and almost wholly concealed; 

 halter of right side showing plainly. Natural size. (Original.) 



Family Tipulidse (The Crane-flies). — This is a large and widely distributed 

 family composed of Diptera having long and rather slender bodies and very long 

 legs; in fact resembling enormous mosquitoes in appearance though a few are 

 very small (Fig. 320). The antennae are generally thread-like and there is a broad 

 V-shaped groove or suture on the top of the thorax. 



The larvae of crane-flies in most cases live in the ground amd feed on the roots 

 of grasses and grain and at times cause much injury in this way. Some exceptions 

 live in decaying wood,' on leaves, in water or elsewhere. There seem to be two 

 generations each year, adults appearing in the spring and fall, and winter is 

 passed as the partly-grown maggot. Injury is most often noticed on low or poorly 

 drained land or where a field has been left in grass for a number of years. Control 

 of these insects, when they are sufficiently injurious to make it pay, is by drain- 

 ing, rotation of crops and plowing early in the fall, when the insects are in the 

 pupa stage just below the surface of the ground, to crush them there. 



