Economic Importance of the Cicadellidae. 



The relation of the Cicadellidie to problems of economic im- 

 portanoe has received a very varying degree of attention from 

 entomologists. The Homopterists, and especially those who 

 have studied this particular family, have alwaj^s been more or 

 less forward in calling attention to their destructiveness. On 

 the other hand, many entomologists have had their attention 

 so taken up with insects M'hose damage has been so much more 

 evident that they have regarded the Cicadellidae as having very 

 little bearing or relation to real economic entomology. But 

 it is not our purpose to say that the one group has been too 

 enthusiastic, and the other too reticent, in recognizing the true 

 economic position of these forms. It is our purpose merely tc 

 discuss the problem in the light of our present-day knowledge, 

 and let the reader decide which group is right, or whether each 

 is but partly right. 



The damage done by the Cicadellidse is that of puncturing 

 the tissue of the leaf or stem of a plant, and then with its 

 efficient little mouth parts sucking up the plant juices. Be- 

 cause of this means of feeding, the damage is seldom seen, cer- 

 tainly not by the casual or superficial observer. The work of 

 insects with biting mouth parts, on the contrary, is readily 

 seen, for the host plant soon is distorted or destroyed by the 

 biting out of portions of the leaves or stems. Thus the work of 

 grasshoppers, beetles, etc., is soon manifest, even though they 

 be present in relatively small numbers. The results of the 

 feeding of a large number of CicadelUdie on a plant may not be 

 noticed, however, till the plant is beyond rescue, for it will 

 retain its form until pumped dry and the leaves begin to curl 

 up and fall. 



There are other reasons, too, why these insects escape notice 

 so often, even though doing damage. In the first place, they are 

 very small, not small as all insects go, but small as compared 

 with the insects which the ordinary person usually observes, 

 and in comparison with many of our main economic pests. 

 They vary considerably in size, many being under 3 mm. in 

 lengt^ while others, especially South American species, may 



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