52 ILUSOIS lUOLOGICAI. MONOGRAPHS [294 



Seplulodes emmcdonia, and the cut-worms of the genus Cirphis (the army- 

 worm genus) are not subterranean. Furthermore, in the subterranean 

 species the relative facility with which the larvae enter the soil, as indicated 

 by the "time required for submergence," as well as by various peculiarities 

 already discussed associated with burrowing, serves as an indication of the 

 extent of the development of the subterranean mode of life in these species. 

 It may be noted, for example, that Sidemia devastatrix presents an extreme 

 case of development of the under-ground mode of life in noctuid larvae. 

 The larva of this species rarely comes above the surface except to molt. 

 UnUke other cutworms it has lost its body pigment and has been aptly 

 described as "half way between a cut-worm and a white grub." Owing to 

 the insufliciency of material and to the sources of error previously men- 

 tioned, it would seem unwise, however, to attach undue significance to the 

 relative lengths of time required for burying given in this table. 



RESISTANCE TO SUBMERGENCE 



The object of the second series of experiments is to determine the 

 relative resistance to submergence in water in various species of noctuid 

 larvae. Immediately after an unusually heavy thunder-shower, several 

 arboreal noctuid larvae were found dead, clinging to the trunks of trees in 

 crevices in the bark, where water had been running during the hardest part 

 of the rain, which had lasted about twenty minutes. Since lightning had 

 not struck in the vicinity, it seemed evident that these larvae were drowned 

 by the water runmng down the tree-trunks. They bore the characteristic 

 marks, to be described later, of drowned larvae. A few days afterward a 

 cut-worm, Feltia subgothica, accidentally left in water for two days in the 

 laboratory, recovered after a number of hours and resumed feeding. This 

 striking difference in the ability to resist submergence in water between the 

 arboreal caterpillars and the subterranean Feltia suggested the use of the 

 length of time during which larvae could resist such submergence as an 

 index as to the extent of the development of their subterranean habit. 

 During early spring land infested with cut-worms, many of which hiber- 

 nate as partly grown larvae, is often saturated with water for days at a 

 time, without seemingly affecting their numbers. We should naturally 

 expect such insects to be able to withstand these conditions successfully and 

 to have developed, in common with subterranean animals generally, a 

 resistance to submergence. Non-subterranean larvae of the ground- and 

 field-strata might be expected to possess this power to a lesser extent, and 

 arboreal species would presumably lack it almost entirely, since the nature 

 of their habitat usually renders it unnecessary for them to withstand 

 extensive drenching. Caterpillars which hibernate in the soil must be sub- 

 jected to water from the melting snows as well as to the spring rains and 

 consequently might reasonably be expected to present the most extensive 

 resistance to submergence of any lepidopterous larvae. 



