THE INSECT WORLD. 



301 



Fig. 339. 



The " cotton-worm" is the larva oi Aletia argillacea, about which 

 many volumes have been written, and whose life history has 

 been thoroughly investigated under the direction of the United 

 States Entomological Commission 

 and the entomologists of the United 

 States Department of Agriculture. 

 To one especially interested in this 

 insect these elaborate reports will be 

 useful and must be consulted. It 

 will suffice here to say that the 

 caterpillars pupate in a loose co- 

 coon spun on the leaves of the 

 plants, and from the dark-brown 

 pupa comes a dull, tawny or clay- 

 colored moth, with indistinct, dark, 

 wavy, transverse lines, and a rather 

 prominent leaden-white spot, more 

 or less margined with black, near 

 the middle of the fore-wings. There 

 are several broods in the course of 

 the year, but only the later ones be- 

 come seriously injurious, the plant 

 then being sometimes entirely de- 

 foliated. A curious feature is that 

 the insects probably do not spend 

 the winter in our territory, but adults immigrate each year from 

 more southern regions. The migrating habit is marked in the 

 later broods maturing on cotton in our country, and the moths 

 have been often seen in great numbers as far north as Canada. 

 As the wings are closely scaled, they do not readily show the 

 wear and tear of long flight, and specimens have been taken 

 in the far north as fresh and bright as if hatched there. It is 

 possible that under favorable circumstances the caterpillars may 

 support themselves on plants other than the cotton, but we 

 have no positive information of their having done so. Of late 

 years the insects are much less injurious than in times past, 

 largely as the result of a diversified agriculture, which has made 

 it less easy for them to increase in abnormal numbers. Planters 

 have also learnt that a prompt application of the arsenites when 



Cotton-worms, from 

 above. 



side and 



