REPORT OF THE ENTOMOLOGIST. 295 



grate to the adjacent fields nearly at the same time, their coming all at 

 once, or within a short time of each other, would ver^^ naturally attract 

 Mttciition. ^loreover, it is very evident that they appeared in greater 

 Miiijibers the present season than they do in ordinary seasons, since none 

 of their eggs were destroyed by being covered with water for too long 

 a tiiiie. 



As stated above, the locusts left the grain fields this season a few 

 weeks after the latter had been harvested, there being no green food 

 tor them to obtain in these fields ; but it is quite probable that, as last 

 x'iisou was a very wet one, there may have been green weeds in the 

 u ill in fields as lat^j in the season as the locusts deposit their eggs, and 

 if such was in reality the case, then we may suppose that many of the 

 lt)custs deposited tlieir eggs in the fields last autumn. This would ac- 

 count for the fact that the locusts were most numerous the present 

 .season on those fields which had not been plowed for over one year. 



From the above facts it would appear that whenever there is a very 

 dry winter and spring in the San Joaquin Valley there will be an abun- 

 dance of locusts in that valley during the following summer ; but when 

 there is an abundance of rain during the winter and spriug months 

 there will not bo an unusual number of locusts during the following 

 summer. 



In the latter part of July I saw several pairs of the Ash-colored Locust 

 {M. einereus) united in coition, but up to the time that I left this valley — 

 the first week in August — I did not see a single pair of the Devastating 

 Locust thus united. 



THE DIFFERENTIAL LOCUST. 



The Differential Locust {Caloptenus diffcr<-niiaJis Thomas) was only 

 about one twenty-fifth as numerous as the Devastating Locust. These 

 two species and the Ash-colored Locust were the only Spine-breasted 

 Locusts that appeared in destructive numbers in the San Joaquin Valley 

 the i^resent season. The only other species of Spine-breasted Locust? 

 that I took in that valley are the Acridhim slwshone Thomas ; the JIcs- 

 perofctiix viridis (Thomas), and the Paroxya {uqht atlantica Sc). 



When I first came to this valley, early in June, the Differential Locust 

 was mostly in the wingless state, there being only about one winged speci- 

 men to ten wingless ones ; by the last week in July the greater number 

 of them had acquired wings. On the 23d of June I saw the first pair 

 united in coition, but the majority of them did not pair until about three 

 weeks later. After coition, and before the eggs are deposited, the 

 abdomen of the female increases very much in size. 



The first egg-mass which I saw this species deposit was deposited on 

 'he 23d of July. The location chosen was a shaded place on the north 

 -^i(le of a row of trees and in a sandy soil. A basin-like hole had been 

 I'.ug in the ground at the base of an ornamental tree, and had been filled 

 uitli water a day or so previously, for the purpose of irrigating the tree, 

 'lit^ female locust had worked her abdomen into the ground on the 

 urci edge of this basin. I first discovered her in this position at about 

 1 o'clock in the afternoon, and at 15 minutes past 4 o'clock she had com- 

 pleted depositing an egg-mass and walked away. 



This egg-mass is about three-fourths of an inch long, slightly curved, 

 and a little less in diameter than an ordinary lead pencil. The si)ace 

 between the uppermost eggs and the surface of the surrountbng earth 

 was filled in with a frothy matter. When freshly deposited, the egg- 

 mass is of a pale bluish color. 



