169 



eluded in any such now existing, it must be the type of a new 

 genus. 



Probably you have heard of the " army worm, "a caterpillar, 

 that invades the cotton fields of the Southern States, and has 

 this year destroyed at least one third of the crop in Louisiana 

 and Mississippi. Several communications have been made to 

 me respecting it, and a correspondent in Mississippi having, as 

 he states, profited by my book on destructive insects, so far as 

 to be able to trace the transformation of the army Avorm, has 

 recently sent to me in a letter some specimens of the moth de- 

 veloped from this worm or caterpillar, with a description of the 

 caterpillar. The moth was new to my collection, and though 

 a good deal injured in transmission, is yet in such a state that 

 the genus might be made out by one familiar Avith the modern 

 genera. From the habits of the larva it seems to me that the 

 insect must approach near to the genus Cosmia. My corre- 

 spondent states that the larva is green, with longitudinal stripes 

 of yellow on the sides, and along the back two black ones separ- 

 ated by a very narrow line of Avhite. They are also studded 

 with black dots, each one producing a black hair. The legs 

 are sixteen. When about to pass into the chrysalis state, the 

 larva draws together the edges of a leaf with silken threads, so 

 as to form a scroll, within Avhicli the transformation takes place. 

 Mr. Say described the moth from very bad specimens, under 

 the name of Noctua xylina. I have been requested to rede- 

 scribe it correctly, and wish to give to it the name of the modern 

 genus, to which it may belong. I expect soon to have the 

 means of raising this insect under my own eye, having sent for 

 eggs, which I shall place on some cotton plants now growing in 

 pots ; and hope in this way to be able to give a more exact and 

 faithful account of it than has heretofore appeared. In Brew- 

 ster's Edinburgh Encyclopedia, article Cotton, there is an 

 account, by Dr. Chisholm, of the " Chenille " destructive to 

 cotton in British Guiana, — an insect, apparently a geometer, 

 differino- from ours. 



