6 BULLETIlSr 966, U. S. DEPARTMENT OF AGRICULTURE. 



individuals living in a rearing cage in the open descended into the 

 earth and when pupal cases, which were not far from the surface of 

 the earth, were examined much later, it was found that the larvae 

 were unchanged and that no moths had issued. 



During October it was observed that larvae were again infesting 

 the same horse-radish patch where first discovered at Arlington, Va., 

 and by October 17 considerable injury had been done to the foliage, 

 quite as much showing at this time as that done by the harlequin cab- 

 bage bug during the season. Where the leaves were dead and dry 

 and were more or less loosely matted together, the larvae were in- 

 variably found; indeed, they infested the entire patch from one end 

 to the other. Larvae were rapidly growing to maturity at this time, 

 feeding sparingly and sluggishly during the cool weather which pre- 

 vailed when under observation in the field. Characteristic injury to 

 the lower leaves as inflicted in midseason is shown in figure 8. 



Larvae feed in colonies at first, but with the period of approach- 

 ing maturity they are soon to be found singly and Avell scattered 

 throughout the field. Some few are protected by white silken webs 

 joining two leaves together or by drawing a single leaf somewhat 

 lightly at the middle near the midrib. The great majority, however, 

 are freely exposed, although sheltered from the sun by overhanging 

 foliage. They feed for the most part near the midribs and near the 

 middle of the plant, seldom near the outer ends, which as the season 

 advances become for the most part dead and dry. 



From the hatching of the larva until its maturity the life history 

 of the species is well told by Buckler (4) as follows : 



The newly-hatclied larva is green, and rather transparent, with a flattened 

 black shining head and dark brown neck-plate, and on the body can just be dis- 

 cerned most minute black dots and hairs ; after eating out little pits and channels 

 from the cuticle, causing transparent blotches on the leaf for about five or six 

 days and acquiring more colour, it becomes of a very pale watery-green as it 

 lays up to moult. 



After the first moult it eats holes quite through the leaf, and its ravages are 

 very perceptible ; its head is black, the back dark green, the belly pale watery- 

 green, the sides of the shining neck-plate dark brown, while the middle of the 

 plate is of the same green colour as that of the back, the wart-like spots are of 

 the ground colour but have dark brown centres bearing single hairs, and a pale 

 ring is at the base of each spot. 



Soon after the second moult it is very dark on the back with a deep and 

 subdued blackish olive-green colour, while the belly has a much lighter tint of 

 the same, these are separated by a spiracular stripe of bright yellow, the head, 

 the side margins of the neck-plate, and the warty spots on the upper surface 

 are shining black, on each side of the back are two very fine and much inter- 

 rupted series of white linear dots, less broken on the second segment to the end 

 of the fourth than on the others, the warty spots on the ventral surface are of 

 the ground-colour, having dark olive-brown centres. 



Directly after the third moult and for a day or so the ground-colour of the 

 larva appears perfectly black, which enhances the brillancy [brilliancy] of the 



