24 THE UNIVERSITY SCIENCE BULLETIN. 



Not only do the nymphs usually look like the adults, but they 

 usually act like them too. They have the curious habit of 

 running sidewise which is so characteristic of the family, and 

 are also capable of jumping, as are the adults, though they are 

 not as active as are the perfect forms. 



The number of molts is usually, if not always, five. There 

 are some records of but four molts in some forms, but if true, 

 it is only so of a very few species. Molting occurs nearly 

 always on the under side of the leaf, and here the molted skins 

 may readily be found, for they are usually firmly attached to 

 the leaf. 



The length of the nymphal stage varies greatly in the differ- 

 ent species. A few species overwinter as nymphs, in which 

 case this stage lasts for several months. In summer, however, 

 the nymphal stage usually lasts for several weeks. Thus Gib- 

 son gives 18 to 35 days, with an average of 25, for the length 

 of the nymphal stage of the clover-leaf hopper, and 20 to 51 

 days, according to temperature, for Drseculacephala mollipes 

 at Tempe, Ariz. Johnson gives from 19 to 37 days for the 

 duration of the nymphal stage of the grape-leaf hopper in the 

 Lake Erie valley. Childs gives above 35 days for the first 

 brood nymphs of the rose-leaf hopper, and about 24 days for 

 those of the second brood in Oregon. Osborn gives ten months 

 as the length of the nymphal stage of Dorycephalus platyrhyn- 

 chus, for this species overwinters as a nymph. 



But very few attempts have been made to determine the 

 length of the life of the adult. Childs, however, has given us 

 some interesting data on this point. He found that the males 

 of the first generation of the rose-leaf hopper die in from four 

 to ten days after mating. Fertile females he found to live a 

 month to a month and a half after mating, while unmated fe- 

 males live very much longer, some specimens being kept for 

 70 days, and a single one for 116 days, death in both cases be- 

 ing due to starvation. Individuals of the second brood were 

 kept alive for 129 days. The unmated male, he states, lives a 

 much shorter period. Of course it is well known that in the 

 case of species which hibernate as adults, both males and fe- 

 males live several months. 



The overwintering of the leaf hoppers is varied. Many pass 

 through the winter as adults, a few as nymphs, and the ma- 

 jority perhaps as eggs. But no set rule can be given regarding 



