232 



Marvels of Insect Life. 



too modest — that if one could eliminate all the natural checks, so that the entire 

 progeny survived, there would be in ten generations (equalling one year) of green- 

 fly " more ponderable substance than in five hundred millions of stout men." Well 

 might Dr. David Sharp say, " Although it is somewhat difficult to make a calculation 

 dealing adequately with the actual facts, yet it is clear that the increase of aphids 

 is such that, drawing as they do their nutriment directly from the plant in its growing 

 state, in the course of two or three years there would be no nutriment available 

 for other animals, except such as might be derived from plants not attacked by 

 aphids. The niunbers of aphidte would be so great that they could not be expressed 

 by ordinary numerical methods, and their increase would be actually limited only 

 by the relations existing between different kinds of plants, and between plants and 

 aphids. This result is avoided by the fact that aphids are themselves the victims 

 of a whole army of Insect enemies." 



The green-fly is a member of the great bug family,^ in which there is no 

 transformation of the individual, but only the acquisition of wings — which in this 



case may be dispensed with for genera- 

 tions. The sub-division to which the 

 green-fly belongs fold their wings when at 

 rest over the body in a roof-like manner, 

 and the fore-wings are of uniform character 

 from base to tip. In the true bugs the 

 wings lie flat on the back, and the basal 

 half is of a thicker, more horny character 

 than the other part. 



Photo by\ [IK. West. 



An Ichneumon's Tent under its Victim. 



Several ot the ichneumon-wasps lay their eggs in the green-fly, 

 and the empty skins of the latter, from which the mature 

 parasite has emerged, may be found commonly upon plants. In 

 some cases the ichneumon-grub leaves the body of its victim 

 from below and spins a tent to hide its later transformation, as 

 shown in this photograph. 



Burnet-Moths. 



The popular name of this pretty group, 

 as well as the scientiflc name of the 

 typical species, appears to be due to a want 

 of precision in the botany of the early 

 entomologists — the salad-burnet and the dropwort being confused, and the name 

 of one used for the English name and that of the other for its scientific appellation. 

 The idea seems to have been that salad-burnet was the food-plant of the caterpillar, 

 and a plant of dropwort was gathered in mistake for it and submitted to a botanist 

 for its scientific name ! But the caterpillars do not feed upon either of these plants. 

 However, the moths are well known as burnet-moths, no matter how they came 

 by the name, and there is no reason why they should not continue to be known by 

 that name. 



The burnet-moths are among the prettiest of our medium-sized moths, and 

 one species at least may be regarded as tolerably common. This is the six-spot 

 burnet,^ whose fore-wings and body are dark green with a bluish reflection, with 

 six crimson spots arranged in pairs. The hind- wings are crimson save for a narrow 

 edging of the same colour as the fore-wings. The stout, short, greenish caterpillar 

 is spotted with black and yellow, and feeds upon low-growing plants, such as clover, 

 bird's-foot, and kidney-vetch. It is full fed in June, and then ascends the tall 



1 lihynchota. - Zygacna filipenduhe. 



