174 DR. V. E. SHELFORD ON THE LIFE-HISTORIES AND 



The further study of these larval pilosity characters and a comparison with 

 pilosity characters of the imagoes would no doubt lead to interesting results. 

 A careful homologizing of the adult and larval areas bearing bristles must, 

 however, be made before such a study can be carried far. It has been noted 

 that bristles representing line A (fig. 57) are present in many representatives 

 of the Cicindela Jlexuosa group, Cicindela 7'egalis group, and a number 

 of other unrelated species. The arrangement of bristles on the head and 

 prothorax of Ctenostoma and some species of Mantichora appears to be definite,, 

 but its relation to the larval arrangement is not clear from casual inspection. 



VI. Relation of Life-Histories and Habits to Environmental 



Factors. 



A, Hibernation. 



The physiological aspect of hibernation has not been studied in detail. 

 Bachmetjew has performed extensive experiments on the temperature relations 

 of insects, and has reported that the insect fluids do not freeze until a point 

 in some cases as low as — 15°C. When the fluids freeze, the temperature 

 rises to about — 1°'5 and the insect never regains life. The rapidity of 

 thawing has no effect on this result ; if cooled ever so low without freezing, 

 the insect regains vitality. He suggests, in connection with hibernation, 

 that the loss of water due to the insect's failure to feed for a long period in 

 the late fall, causes an increased concentration of the body fluids which lowers 

 their freezing-point. Greeley found that low temperature caused certain 

 Protozoa to encyst or produce spores. Tower found that Leptinotarsa loses 

 30 per cent, of its weight, 3 per cent, excreta and 27 per cent, water, in 

 preparing for hibernation, and was unable to prevent this preparation by 

 experimental means in beetles that normally hibernate. 



The larvge of all species studied pass through at least one winter. With 

 the approach of cold weather (late September) they dig their burrows deeper, 

 piling the sand beside the opening in a single heap. They finally stop 

 digging and close the mouth of the burrow with soil, go to the bottom and 

 remain until spring (observed by Criddle, Giinther, and Enock in the case of 

 species not here considered). When brought into the vivarium and kept at 

 27°-30° C, they remain active for two or three weeks longer than out of 

 doors. They finally close their burrows and go to the bottom, notwithstanding 

 the higher temperature. Individuals fed continuously during the time they 

 are kept under these abnormal conditions, were not notably influenced as to 

 the time they closed their burrows. If the soil is kept dry they prepare for 

 hibernation sooner than when it is very moist. 



If the temperature be raised to 36°-40'^ C. and the soil and surrounding- 

 atmosphere kept moist, larvge of C. hirticollis, tranqueharica, and scutellaris 



