14 
filled only with the same frothy matter that surrounds each egg, which 
matter occupies all the other space in the burrow not occupied by the 
eggs. The whole plan is seen at once by a reference to the figure re- 
ferred to, which represents, enlarged, a side view of the mass within 
the burrow (a), and a bottom (b) and top (c) view of the same, with the 
earth which adheres to it removed. 
Number of Egg masses laid by a single Female. — Yersin concludes, refer- 
ring to the European migratoria, that eggs are laid thrice, at intervals 
of about a month, while Kriinitz, Kefer stein, and Stoikowitsch t also 
declare that they are laid in three different masses. Professor Whit- 
man, in his 1876 experiments, had a female which laid about the middle 
of July, aud died September 9, without laying again, though eggs were 
found in the ovaries at death. The time between the first and second 
laying, observed by Korte, was 6 days. Mr. Aughey, from experiments 
made in 1876, found the interval still shorter, ranging from 2 to3days; 
but he requests us to add that other experiments, not recorded, showed 
a much longer interval between the periods, extending in some cases to 
20 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 con- 
stant. It is natural to suppose 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 intes- 
tate, and it was very generally noticed that they laid no eggs. 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 maybe subjected 
to, and that sterility is one of tbe most frequent consequences of such 
change. It was upon this general rule that the late JB. D. Walsh, knowing 
nothing of the return mig ration, based the theory that the Rocky Moun- 
tain locust could never thrive in the temp orary region, but would become 
intestate and perish there. In 1876 we had measurable success in get- 
ting spretus to lay eggs in confinement. In 1877, though we made far 
more strenuous efforts with the insects that hatched in Texas and Kan- 
sas, yet we signally failed. Of many thousands which we hatched in 
St. Louis and endeavored to rear under the most favorable circum- 
stances in vivaria containing growing grain, most of them died in from 
3 to 8 days from hatching. We succeeded in bringing a few through 
the third and two through the fourth molt. At Carboudale, III., from 
t See Koppen, p. 36. 
