20 BULLETIN 967, U. S. DEPARTMENT OF AGRICULTURE. 



trmngulin can secure. If the eggs in a capsule fall short of the 

 minimum requirement to carry the larva to maturity it perishes ; if 

 they exceed this minimum the difference is registered by the size of 

 the beetle which develops. Consequently, in a given species there is 

 great variation in size of the adults. The third larva is injuriously 

 affected by insufficient or excessive soil moisture ; however, the vari- 

 ation or limits in which it is safe are commonly prevalent in semiarid 

 regions during spring and early summer. The pupae are exceedingly 

 sensitive, being injuriously affected by excessive soil moisture, han- 

 dling, high temperature, or a soil rich in humus. Even prolonged 

 high humidity injures them. Many on which a little earth dropped 

 or that are exposed during an examination gradually turn dark and 

 decay. 



The coarctate larvae, on the other hand, are resistant to handling, 

 to exposure, to drying, or to any soil disturbance that does not crush 

 them. They have even become overgrown by saprophytic soil fun- 

 gus while in storage without loss of vitality. Excessive soil moisture, 

 however, or continued high humidity, such as is necessary to pro- 

 duce conditions that favor the development of fungus, is usually 

 detrimental. The position of the coarctate larvae in the soil facili- 

 tates drainage, standing, as they do, on end in the old exuvium and 

 touching the soil only in the dorsal region of the prothorax. Treat- 

 ment to which they were submitted by the writer also demonstrated 

 their ability to withstand extreme exposure and drying. Coarctate 

 larvae that remained for months in open containers without soil, in 

 open containers on dry soil, and buried in pulverized dry soil have 

 transformed shortly after being placed in moist soil. 



When coarctate larvae are very dry during the spring and early 

 summer the rigid skin often splits immediately if water is thrown 

 directly upon it, the larvae emerging within a few minutes. Such 

 dry coarctate larvae also soon transform when placed on moist earth. 



Coarctate larvae that are kept dry during the spring and summer 

 may or may not give forth the third larvae when moistened in the 

 fall. The instance cited of seven that were buried and forgotten 

 and later found to have become third larvae, six of which reverted to 

 the coarctate stage, illustrates another mode of behavior of such 

 specimens. During the time they were buried the insect ary was 

 flooded by run-off irrigation water from an adjacent field, The 

 floor was barely covered by water and dried quickly, especially in 

 the end where the box was buried. It is possible that enough water 

 penetrated the box to initiate development, but not to complete it. 

 The six larvae that resumed the coarctate stage did so as a protective 

 measure, or else the coming of cold weather caused this resumption. 

 The writer attributes their reversion to one of these alternatives. 

 Granting the correctness of these deductions, it indicates a more 



