472 LEPIDOPTERA. 



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

 comes out a Platygaster fly, like its parent. This last trans- 

 formation 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 appearance 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. Without doubt such wise- 

 ly 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 en- 

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

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

 ance, and united efforts, to contrive and carry into effect 

 other means for checking their ravages. 



Between the years 1841 and 1847, canker-worms almost 

 entirely disappeared in the vicinity of Boston. At the latter 

 date, there was a visible increase of them here, and their 

 numbers have rapidly augmented every subsequent year. 

 In a few years more, unless checked by natural or artificial 

 means, they will probably prove as destructive as at any 

 former time. The writer of this work has given repeated 

 warning of these facts in the public prints, and has pointed 

 out the remedies to be applied.* 



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 



* See Prairie Farmer, Vol. VIIT. p. 172, for June, 1848. Massachusetts Plough- 

 man, for June 24, 1848, Nov. 23, 1850, and May 17, 1651. Boston Cultivator, Nov. 

 24, 1849. New England Farmer, Vol. II. p. 252, for August, 1850. 



