THE CANADIAN ENTOMOLOGIST 77 



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nor are they especially exposed to shocks that might shake them loose from 

 their hold. And Guthrie is mistaken in saying that their feet are not well 

 adapted for smooth surfaces. It is true that the feet are lacking in any kind 

 of a pad or sucker; and it is not likely that the two or three clubbed or genicu- 

 late setae— the so-called tenent hairs — that in some species project over the 

 usual pair of curved pointed claws, are anything more than tactile in function. 

 But however they manage it, the thirty or forty species that I have observed 

 in life, whether with two claws on each foot or only one, and with or without 

 tenent hairs, could all run nimbly on dry, polished glass, even back downwards; 

 and such a surface is infinitely harder and smoother than any they ever encounter 

 in their natural habitat. 



In support of his opinion that the ventral tube is an <5rgan of attachment, 

 Lubbock says that if a Sminthurus is laid on its back and a piece of glass is brought 

 within its reach, "the animal will endeavour to seize it with the feet, but at the 

 same time it will project one or both of the ventral tentacles and apply it, or 

 them, firmly to the glass, emitting at the same time a drop of fluid which, no 

 doubt, gives a better held." This surmise may sound plausible in the par- 

 ticular instance, but an extended observation of the actions of different species 

 as regards the ventral tube leads to another view of the probable function of the 

 organ. 



The Collembola are all extremely sensitive to any lack of humidity in their 

 surroundings. Most species, if put into a dry vial, will die and begin to shrivel 

 up within an hour. The only way to keep them alive in captivity for any length 

 of time is to put in the vial some source of moisture such as wet, rotten wood 

 or damp filter pap.er. Evaporation through the thin epidermis i.s so rapid, that 

 it appears not unlikely to me that the ventral tube has to do with supplying 

 or regulating the large quantity of moisture the insect requires. 



This conjecture seems to be borne out by the conduct of more than one 

 species For instance, a yellow Papirius — (a genus closely related to the Smyn- 

 thurus mentioned by Lubbock) found in the autumn under dead leaves of hard- 

 wood forests, stands high on its legs, neither its ventral tube nor any other part 

 of its abdomen normally touching the surface it rests on. In a vial, it has no 

 trouble in walking on the glass in any position; and it remains for hours and 

 even days clinging to the glass, back downwards, by its feet alone, maintaining 

 its hold without any help whatever from the ventral tube. 



Of a dozen or so of this species kept in a vial with the usual morsel of moist, 

 rotten wood or damp filter paper, the majority remain thus motionless for long 

 periods. Then suddenly, with startling swiftness, one of them shoots out its 

 ventral filaments on either side of its body, and applies them closely to the glass 

 along their whole length, always — so far as I have observed — where there is a 

 film of moisture on the glass. The filaments, which are tubular and provided 

 with a number of sucker-like glands at the ends, are longer than the insect's 

 entire body, but are evidently stowed away by the smaller apical half telescop- 

 ing into the larger basal section. After leaving tke filaments in contact with 

 the glass for a minute or two, the insect draws them in as swiftly as it shot them 

 out, changes its position slightly, and darts them out again. This performance 

 may be kept up for ten minutes or so, and then finally drawing in the filaments 

 permanently, the insect lapses into quietude again. 



