116 



Cameron ('13, p. 190) speaks of the resistance to droAvning of elaterid 

 larvae as follows : "I myself have kept specimens of the larvse of 

 Agriotes lineatus, our commonest wireworm, in water for as long as 

 six days without their being drowned, but those which were thus 

 treated for a period of seven or eight days did not generally recover 

 from the deleterious effects of immersion. Leather- jackets and sur- 

 face caterpillars submitted to the same treatment succumbed in a much 

 shorter time, one to two days for the caterpillars, depending on their 

 state of development — much shorter time than this for very young 

 forms — and from one to three days in the case of leather-jackets, the 

 latter being in all cases fully mature." 



Dr. R. D. Glasgow informs me that it is probable that the soil- 

 inhabiting white-grubs, Lachnostcrna, may be able to close their spira- 

 cles when the soil is saturated and thus resist drowning, as in the case 

 of the European Melolontha (Cf. Henneguy, '04, p. 105 ; Packard, '98, 

 p. 442). With this closure of the spiracles there is probably corre- 

 lated a power to resist a lack of oxygen and an excess of COo. In any 

 case, this is a subject worthy of experimental investigation. Cam- 

 eron ('13, pp. 197-199) has called attention to the marked resistance 

 to a lack of oxygen found in muscid (dipterous) larvse; they endure 

 submersion for long periods and recover rapidly. He says (1. c, p. 

 198) : "A faculty of resistance and power of adaptability to adverse 

 circumstances is of peculiar advantage to the insect inhabitants of the 

 soil, which, owing to the varying climates and atmospheric conditions, 

 are often subjected to the most severe extremes of heat and cold, wet 

 and drouth. The more sluggish maggots of Diptera have a greater 

 plasticity than the active larv?e of predaceous Coleoptera. On consid- 

 ering these two orders by themselves, amongst Diptera the larvse of 

 Muscidcc have a greater power of resistance generally than the larvse 

 of Nematocerous and Brachypterous families, whilst among Coleop- 

 tera the grubs of Rhynchophora are not so easily affected as those of 

 Carahidcc and Staphylinidcc and other active families. This is just 

 what we might expect, seeing that nature, which has deprived Dipter- 

 ous maggots and Weevil grubs of legs that they might readily escape 

 danger, has compensated them to some extent by endowing them with 

 a greater power of resistance to adverse conditions." 



Upon the black soil prairie the snout-beetles Sphenoplwrus 

 abounded in the roots of swamp plants, where they were particularly 

 liable to submersion with varying rainfall. It is, however, possible that 

 this resistance may be entirely independent of the footless condition. 



The optimum soil conditions for insects have thus been summa- 

 rized by Cameron ('13, p. 198) as follows: "Soils that are of a light 

 and open texture are, as we have already seen, the ones most fre- 

 quented by soil insects, all other conditions, such as those of food, being 



