Practical Cons i derations. 



143 



subject, know full well that the large proportion of insects 

 that hibernate on or in the ground, are more injuriously 

 affected by a mild, alternately freezing and thawing winter, 

 than by a steadily cold and severe one ; and the idea has 

 quite generally prevailed, that it was the same with regard 

 to our locust eggs. But, if so, then it is more owing to the 

 mechanical action which, by alternate expansion and con- 

 traction of the soil, heaves the pods and exposes them, 

 than to the effects of the varying temperatures. 



Second — That suspended development by frost may 

 continue with impunity for varying periods, after the em- 

 bryon is fully formed and the young jbsect is on the verge 

 of hatching. Many persons, having in mind the well 

 known fact that birds' eggs become addled if incubation 

 ceases before completion, when- once commenced, would, 

 from analogy, come to the same conclusion with regard to 

 the locust eggs. But analogy here is an unsafe guide. 

 The eggs of insects hibernate in all stages of embryonic 

 development, and many of them with the larva fully formed 

 and complete within. The advanced development of the 

 locust embryo, frequently noticed in the fall, argues nothing 

 but very early hatching as soon as spring opens. Their 

 vitality is unimpaired by frost. 



Experiments to test the Influence of Moisture upon 

 the Eggs. — The following series of experiments was made 

 with eggs also brought from Manhattan, Kansas. They 

 were dug up in December, and were sound, and much in the 

 same condition as those in the preceding series. 



The water in all but the last three, or Experiments 23, 

 24 and 25, was kept in my office at the temperature already 

 stated, and changed only when there was the least tendency 

 to become foul. In the alternate submergence and draining, 

 the eggs were submitted to the most severe hygrometric 



