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MISC. PUBLICATION 318, U. S. DEPT. OF AGRICULTURE 



Figure 79. — Horsefly. 



Horseflies. — In the horse-and-buggy days many runaways were 

 caused by large black flies lighting on the horse. The group of flies 

 to which this species belongs are called horseflies. 

 They vary considerably in size and can be dis- 

 tinguished by the peculiar shape of the head, 

 which is nearly all eyes and fits over the front part 

 of the body caj) fashion. The adults have two 

 wings and piercing mouth parts. They feed on a 

 number of animals. Horseflies have complete life 

 changes and spend the winter as larvae in mud. 

 Although these insects are pests, there is no effec- 

 tive control except drainage of the marshy areas 

 in which many kinds breed. The black horsefly 

 pictured here is Tab arms atrutus. This species is 

 from % to V/ 8 inches long. 

 Robber flies. — Can it be possible that when man desired more speed 

 in the air he looked to the robber flies ? Most robber flies are rather 

 large. Even though they have but two 

 wings they are capable of flying very fast. 

 They feed almost entirely on other insects. 

 The head of the robber fly somewhat re- 

 sembles that of the horsefly, but its neck 

 is much longer. The adult has piercing 

 mouth parts. These insects usually winter 

 as larvae or pupae in the ground, 

 where the larvae feed on worms and 

 larvae of other insects. Like all other 

 Diptera, the robber fly has complete life 

 changes. The one shown here is Prom- 

 achus ruftpes, which attains a length of from 1 to 1% inches. 

 Mosquitoes. — What person has not heard the buzzing of a mos- 

 quito or felt the mouth parts pierce an exposed part of the body? 

 This group of Diptera possibly causes as much annoyance to people, 

 especially picnickers, as any other insect. It is 

 only the female mosquito that can bite, and not 

 all kinds of mosquitoes feed on man or animals. 

 In addition to causing annoyance from feeding, 

 some mosquitoes are responsible for carrying dis- 

 eases such as malaria and yellow fever. Malaria 

 is a major health problem in this country. All 

 mosquitoes have a long, narrow body with com- 

 paratively long legs and two wings. The life 

 changes are complete. The larvae, or "wigglers," 

 are found in stagnant water. Mosquitoes breed 

 commonly in rain barrels, cisterns, ponds, and 

 other places where water stands for a few days. 

 Such accumulations of water should be tightly 

 covered, or the surface treated with a light film of kerosene or oil 

 every week. If possible, stagnant pools should be drained. Mos- 

 quitoes are usually much smaller than crane flies, and can be dis- 

 tinguished from crane flies by the tiny hairs on the margins of the 

 wings. The one shown here is the yellow-fever mosquito (Aedes 

 aegypti), which is about three-sixteenths of an inch long. 



Figure 80. — Robber fly. 



