SOME INSECT ADAPTATIONS 



25 



beetles, diving beetles, and back swimmers (Fig. 9, A). Insects 

 like the mosquitoes (Fig. 53) and the water skaters, on the other 

 hand, remain on top of the water, where they are sustained upon 

 the surface film by their long slender legs, just as is a needle 

 which is carefully placed on top of the water in a tumbler. In- 

 sects that burrow in the ground possess legs fitted for digging; for 

 example, the mole-cricket (Fig. 9, B) and the young of the 

 cicada (Fig. 9, C). Many insects, like the 

 flea (Fig. 32), do not fly because they lack 

 wings, but others cannot fly even with wings, 

 either because these organs are too small 

 for the weight of the body (Fig. 26) or, as 

 is the case with some beetles that are found 

 under stones and logs, their wings have 

 grown together so that they cannot be 

 spread. 



Respiration. — The breathing methods 

 or respiration of aquatic insects are often 

 very different from those of their relatives 

 living on land. Since these insects live 

 under the water, they must either come to 

 the surface for air (Fig. 55), or else get their 

 air from the water. Many of them, like 

 the young of the may flies (Fig. 10) and 

 damsel flies, possess filamentous or leaf-like 

 projections called tracheal gills, by means 

 of which the air mixed with water is collected in the air tubes 

 and then carried throughout the body. 



Securing Food. — Mouth Parts. — Adaptations for the 

 purpose of getting food are especially important, since those 

 insects with biting mouth parts, like the grasshopper, can be 

 destroyed by spraying their food with a poison such as Paris 

 green; whereas those with piercing and sucking mouth parts 

 feed only on juices from within the plants or animals they at- 

 tack, and must be destroyed in some other way. The mouth 



Fig. 10. — Young of 

 may fly showing 

 tracheal gills (k). 

 (After Sedgwick.) 



