BITING AND SUCKING INSECTS. 13 



the grass family, gradually increasing in size, and 

 moulting at intervals. In a few weeks they become 

 nearly full grown, but instead of changing to a quiet 

 chrysalis state, they simply moult again and continue 

 feeding as before. In these early stages, which cor- 

 respond to the larva and chrysalis, they are called 

 nymphs. The older nymphs (</) are nearly as large 

 as the full grown bugs, differing mainly in the 

 absence of wings. In about a week they again moult 

 and come forth as adult bugs. Grasshoppers, crick- 

 ets, and all true bugs, undergo these incomplete 

 transformations. 



BITING AND SUCKING INSECTS. 



Insects take their food in two ways: some insects 

 bite, others suck. The former, of which the Colorado 

 Potato Beetle is an example, are provided with jaws 

 by which they can gnaw the surface of the food- 

 plant. The latter have, instead, a pointed, tube-like 

 beak which they can insert into the tissues of their 

 host-plant, and suck out the sap. 



On account of this difference in feeding habits 

 some insects can be destroyed by coating their food- 

 plants with poison — the Colorado Potato Beetle for 

 example — while others, like the plant-lice or 

 Chinch Bug, must be treated with some insecticide 

 that kills by contact, 



NATURAL ENEMIES OF INJURIOUS INSECTS. 



Injurious insects have many natural enemies to 

 contend with. Among the larger animals they are 



