17 



h«s done feeding and weighs 95 grains. It has thus in 

 this short space of time increased its bulk 9590 times, and 

 if we consider the digested food it has passed away, it has 

 eaten 15,000 times its weight of food. 



The larva of a Privet Hawk weighed 170 grains ; there- 

 fore it had consumed 13,600 times its weight ; and a fine 

 larva of an Atropos, or Death's Head Moth, weighing 210 

 grains, 16,800. But Lyonet found that the larva of Cossus 

 Ligniperda, which remains nearly three years in that state, 

 increased to 72,000 times its original weight, and if wo 

 consider the time it was growing, feeding the whole time, 

 it could not have consumed less than 100,000 times what it 

 weighed when it first left the egg. Well may they leave a 

 desolated tract for a while behind them where they abound, 

 and are free from those compensating media which nature, 

 in her wild and unfettered province, almost invariably 

 supplies, the poison and the antidote^the overwhelming 

 accumulations of larvse, the unusual collection of birds, 

 and other insects which prey upon them. 



THE AHTERIAL, OE VASCULAK SYSTEM. 



This, in the insect arrangement, is very simple. It 

 consists of one large dorsal vessel, that can be very easily 

 discerned in larvte that have smooth skins. It runs from 

 the tail to the head, whore it divides into two or three 

 branches. In each segment there is a valve which allows 

 the blood to flow in, but prevents it returning. The blood 

 is thin, transparent, and colourless, having small corpuscules 

 or blood globules, floating in it ; these are also colourless. 

 The blood, it is said, passes along this great dorsal vessel 

 before it arrives at the head, when it is poured out into the 

 neighbouring tissues ; it traverses every part of the system 

 and enters again the dorsal vessel through the valves. 

 There is something very unsatisfactory in this theory of 

 the arterial, or blood circulation of insects. I think it will 

 ultimately be proved, however far it may have to travel, 

 that it is conveyed in blood vessels, no doubt very fine, and 

 from this cause alone has hitherto escaped observation. 



