INTERVAL BETWEEN DIFFERENT EGG-LAYINGS. 227 



■which laid about the middle of July, and died September 1), without lay- 

 ing again, though eggs were found in the ovaries at death. The time 

 between the first and second laying, observed by Koite, was six days. 

 Mr. Aughey (App. 8), from experiments made in 187G, found the interval 

 still shorter, ranging from two to three days; but he requests us to add 

 that other experiments, not recorded, showed a much longer interval 

 between the periods, extending in some cases to twenty days. It would 

 thus appear that there is the greatest diversity in the time intervening 

 between the periods of egg-laying, and that the number of egg-masses 

 formed by one individual is by no means constant. It is natural to sup- 

 pose that there will be great difference in individual prolificacy, and we 

 are also of the opinion that there is great difference in this respect in 

 different generations — those that hatch in the Permanent region being 

 more prolific than those which hatch in the Temporary region. This 

 opinion is not only warranted by the general experience of farmers, but 

 also by experiment. As compared with those of 1876, the autumn flights 

 of 1877 were for the most part intestate, and it was very generally 

 noticed that they laid no eggs. (App. 12.) There is, as we have seen 

 in the preceding chapter, the best of reasons for believing that these 

 flights were not from the Permanent region, but consisted mainly of 

 insects that had bred in the Temporary region. 



It is well known that the reproductive organs are easily affected by 

 any sudden change of climatic conditions which animals may be sub- 

 jected to, and that sterility is one of the most frequent consequences of 

 such change. It was upon this general rule that the late B. D. Walsh, 

 knowing nothing of the return migration, based the theory that the 

 Eocky Mountain locust could never thrive in the temporary region, but 

 would become intestate and perish there. In 1876 we had measurable 

 success in getting spretus to lay eggs in confinement. In 1877, though 

 we made far more strenuous efforts with the insects that hatched in 

 Texas and Kansas, yet we signally failed. Of many thousands which 

 we hatched in Saint Louis and endeavored to rear under the most favor- 

 able circumstances in vivaria containing growing grain, most of them 

 died in from three to eight days from hatching. We succeeded in bring- 

 ing a few through the third and two through the fourth molt. At 

 Carbondale, 111., from Minnesota eggs, Mr. Thomas had better luck, and 

 reared several to the winged condition. We repeatedly dispatched liv- 

 ing specimens both of the pupae and the mature insects from Texas, 

 Kansas, and Iowa, to our office-clerk, Mr. Tb. Pergande^ Saint Louis; 

 but with no more favorable results, as he entirely failed to obtain eggs, 

 and the females, when dead, were found, upon examination, to contain 

 none. This want of fecundity, though not universal, was quite general 

 with the insects of 1877, and is in keeping with the general experience 

 as to the sickly and degenerate nature of the brood. 



It is quite manifest, therefore, that in answering the question we have 

 iust asked we can do so only in a general and qualified manner. The num- 



