Jan. IS. I9IS Three-Cornered Alfalfa Hopper 355 



process is repeated. This was continued for three-quarters of an hour and then, after 

 a minute's rest, with one final effort an opening was split on the dorsum of the entire 

 thorax and head and the delicate white insect began to appear. The spines on the 

 thorax were first pulled out, and then the insect continued its wriggling and gradually 

 the abdomen was pulled from the old abdominal skin, the larva all the time working 

 itself forward over the cast skin of the head. The legs were not entirely withdrawn 

 until after the last segment of the abdomen was freed. The insect, then crawling 

 the rest of the way over the head of the exuvia, came to rest on the plant just ahead 

 of the cast skin. There it remained resting for 30 minutes, during which time the 

 newly exposed tissue was becoming hard and firm and accustomed to the sur- 

 roimding atmospheric conditions, after which the insect began feeding. 



THE ADtTLT STAGE 



The adults are strong, quick flyers. They are wary and, like the young, 

 upon the approach of danger hastily move to the opposite side of a plant; 

 then, as the enemy comes closer, with a spring they are off — how swiftly 

 can only be appreciated by one who has been unexpectedly hit on the 

 face or in the eye by an alfalfa hopper. 



As obser\-ed in the cages kept for the purpose of determining the 

 number of generations, the males are more numerous than the females, 

 being in the proportion of 4 to 3. The female, after issuing from the last 

 nymphal stage, requires from 8 to 10 days to complete her development. 

 During this time she is feeding, and at the end of the period copulation 

 takes place. A few days thereafter oviposition begins. The males die 

 shortly after copulation, while the females lay eggs for a considerable 

 period. Four hibernating females were placed in a cage on February 13, 

 and on February 26 several eggs were laid; oviposition was continued 

 until May 5, the females dying soon thereafter. Thus there was an egg- 

 laying period of 70 days. A maximum of only 50 eggs was secured from 

 a single female. The four mentioned above laid a total of 1 29 eggs, or an 

 average of 32 each. It is possible, however, that these may have 

 deposited eggs previous to entering hibernation. Eight other females 

 deposited from 7 to 19 each. These numbers all seem small for maxi- 

 mums, but they were secured under unnatural cage conditions. Without 

 much doubt a larger number than this, possibly as many as a hun- 

 dred, are deposited by single females, when they are free and unham- 

 pered, as in the field. 



SEASONAL HISTORY 



HIBERNATION 



The seasonal history of this species varies during different years, the 

 variation quite naturally being due to the climatic conditions, especially 

 the minimum temperature of any particular year. This variation 

 appears largely during the winter months, when the species is supposed 

 to be hibernating. At Tempe, Ariz., during a mild winter, such as the 

 last one (1913-14), the species does not hibernate at all in the adult 

 stage. Adult males and females were taken feeding on alfalfa every 

 week during December, January, and February of last winter. Mr. 

 Gibson, who made the January and February observations at Tempe, 

 discovered that eggs deposited in the late fall months hatched on warm 

 days, but the nymphs were usually killed during the cold nights following. 

 During winters when the minimum temperatures are much lower the 

 species goes into hibernation both as eggs and adults. During the 

 winter of 1912-13 such conditions as those just mentioned were noted. 



