LEPIDOPTERA. 341 



it becomes a chrysalis within the same shell, and in due time 

 comes out a Platygastcr fly, like its parent. This last transfor- 

 mation Mr. Herrick found to take place towards the end of June, 

 from eggs laid in November of the year before ; and he thinks 

 that the flies continue alive through the summer, till the appear- 

 ance of the canker-worm moths in the autumn affords them the 

 opportunity of laying their eggs for another brood. As these 

 little parasites prevent the hatching of the eggs wherein they are 

 bred, and as they seem to be very abundant, they must be of 

 great use in preventing the increase of the canker-worm. With- 

 out doubt such wisely appointed means as these were once 

 enough to keep within due bounds these noxious insects ; but, 

 since our forests, their natural food, and our birds, their greatest 

 enemies, have disappeared before the woodman's axe and the 

 sportsman's gun, we are left, to our own ingenuity, perseverance, 

 and united efforts, to contrive and carry into effect other means 

 for checking their ravages. 



Apple, elm, and lime trees, are sometimes injured a good deal 

 by another kind of span-worm, larger than the canker-worm, and 

 very different from it in appearance. It is of a bright yellow 

 color, with ten crinkled black lines along the top of the back ; the 

 head is rust colored ; and the belly is paler than the rest of the 

 body. When fully grown, it measures about one inch and a 

 quarter in length. It often rests with the middle of the body 

 curved upwards a little, and sometimes even without the support 

 of its fore-legs. The leaves of the lime seem to be its natural 

 and favorite food, for it may be found on this tree every year ; 

 but I have often seen it in considerable abundance, with common 

 canker-worms, on other trees. It is hatched rather later, and 

 does not leave the trees quite so soon as the latter. About or 

 soon after the middle of June it spins down from the trees, goes 

 into the ground, and changes to a chrysalis in a little cell five or 

 six inches below the surface ; and from this it comes out in the 

 moth state towards the end of October or during the month of 

 November. More rarely its last transformation is retarded till 

 the spring. The females are wingless and grub-like, with slen- 

 der thread-shaped antenna?. As soon as they leave the ground 

 they creep up the trees, and lay their eggs in little clusters, here 



