PLANT LICE. 



237 



FIG. 284. 



The Indian Chinch 

 Bug. Immature 

 form. (Magnified.} 

 (From Distant.} 



prevent the bugs from gathering in them to eat the young grain. As a 

 rule no insecticides can be used against these hard bugs at a sufficient 

 strength to kill them, but only to drive them away or to make the plant 

 distasteful to them. 



Green Fly and Plant Lice (Aphidse). 



Plants are often found to be covered with colonies of tiny black 

 or yellow insects, which cluster thickly on the leaves 

 and twigs. Such plants, as a rule, have an unhealthy 

 appearance and the lower leaves are covered with a 

 sticky substance. This appearance of the leaf and 

 plant is a symptom of one of the sucking insects 

 described here ; if the little insects move about, 

 are not covered with a scaly covering and have the 

 two little tubes projecting from the abdomen (see 

 fig. 286), then it is safe to conclude that the insects 

 are plant lice, also known as green fly or aphides. 

 The insects are small, the largest not more than one- 

 tenth of an inch long ; each has three pairs of legs, 

 a sharp suctorial beak, eyes, and feelers; there are 

 also the two short tubes or knobs which project from 



the upper surface of the abdomen. Some are winged, others un winged. 

 The life history of these insects varies very much according to locality, 



climate, etc. As a rule, the colonies are composed 



only of females which may be winged or unwinged, 



and all of which produce young alive, all females. 



Males are not found and the young attain maturity 



in a few days from birth, when they too bring 



forth young. The rate of reproduction is thus 



enormous, the colony increasing very rapidly in 



number. When the colony is small, it is found that 



the females are unwinged ; later on winged indivi- 

 duals appear, the wings forming gradually as they 



do in other insects which have no metamorphosis- 



These winged females fly from plant to plant spread- 

 ing the colony over a large area ; wherever they 



settle down they found a fresh colony, and the rate 



of multiplication and spread becomes enormous. 



This occurs typically in the species which are found attacking crops 



in India, and it is probable that at particular seasons of the year, males 



are produced and a sexual generation found, The life history f of no 



The 



Fia. 285. 

 Til-seed 



Bug. 



(Magnified.) (From 

 Distant.} 



