1920] Ball: Life Cycle in Hemiptera 143 



little is known except for one species in which the life cycle 

 requires 17 years and a variety in which this number is reduced 

 to 13. Popular opinion credits the other species with two-year 

 cycles. According to W. T. Davis this originated with Jseger in 

 the "Life of North American Insects" published in 1854 and 

 he credits the information to Pontedera. Whether Pontedera's 

 statement was the result of experiment or only a guess has 

 apparently never been tested. Absolute fixity of the 17 and 13' 

 year cycles is, however, one of the marvels of nature and should 

 be an everlasting refutation of any suggestion that insect 

 activity is subject to fluctuation like the ever changing 

 thistledown. 



The Cercopid^ or Frog-hoppers show a marvelous adapta- 

 tion in their froth making habit and they have apparently 

 depended largely upon this rather than other modifications for 

 their protection. All of our local species have a single annual 

 generation and all but one pass the winter in the egg stage. The 

 variations in this single generation will be discussed under that 

 head in the next family. 



The Membracid/E or tree-hoppers are celebrated for the 

 wonderful variety and complexity of their adaptations to their 

 food plants. When it comes to the life cycle on which most of 

 these adaptations are based, it is found to be fundamentally 

 very simple. 90 per cent or more of our species have a single 

 annual generation and more than 90 per cent pass the winter in 

 the egg stage. The tree hoppers of the genus Telamona, for 

 example, feed very largely on the sap of the trees and mainly 

 on the tender growing twigs. They find optimum conditions 

 for such feeding only during the comparatively short period in 

 which the tree is making its growth. They also must find a 

 location and deposit their eggs while the wood is still soft and 

 tender ; otherwise they will be unable to penetrate to a sufficient 

 depth to protect the eggs from predacious and parasitic insects. 

 The result is that we find that they, with a possible exception, 

 pass the winter in the egg stage and have a single annual gen- 

 eration. The overwintering eggs in the twigs hatch almost 

 with the first growth in May. The nymphs mature in June. 

 The adults lay eggs in July and August and the cycle is finished. 



In the case of Ceresa bubalis (the Buffalo tree-hopper) and 

 its vegetation-feeding allies the need of haste is not so great as 

 their food plants, Composits, Legumes and others, grow all 



