26 



The Bulletin. 



Life History, etc. — The butterflies appear in very early spring and 

 lay the yellow qggs on cabbage and related plants. The eggs hatch to 

 small green ''worms" with velvety skin, which lie flat on the surface of 

 the leaf. When grown the worm or caterpillar is about an inch long 



Fig. 10. — Larva (or worm) of imported Cabbage Worm on cabbage leaf. 

 Natural size. (Photo by Z. P. Metcalf.) 



and it then changes to the "chrysalis," or pupa, and from this the adult 

 butterfly emerges after a few weeks. There are a number of broods each 

 season, and the last brood of worms to reach maturity in the fall change 

 to the chrysalis state and remain in that condition over winter, emerg- 

 ing as butterflies in the spring. The chrysalis is not enclosed in a web 

 or cocoon, but is entirely naked and is usually suspended from the under 

 side of a leaf, stone, fence-rail or other object by a loop of thread around 

 the body. The butterflies are very conspicuous everywhere all through 

 the season — the small white butterflies seen flittering about cabbage are 

 almost invariably of this species. There are several kinds of yellowish 

 butterflies of about the same size that are sometimes seen in our gardens, 

 but which have no connection with the cabbage worms. 



Natural Enemies. — The imported cabbage worm is destroyed by a. 

 number of natural enemies. Here, again, the English sparrow comes in 

 for some good work, as he has been observed to pick off worms from 

 cabbage in gardens. Indeed, this bird seems to be fond of staying 

 among the cabbage rows, and almost certainly it does really good work 

 (especially in town and village gardens) in destroying cabbage lice, 

 harlequin bugs and cabbage woruis. 



Dr. Chittenden says,* "The most important of its insect enemies are 

 small parasites, all introductions from Europe. One of them was pur- 

 posely imported from England in 1883 and during the autumn of 1904 

 held the host (cabbage worm) under complete control at Washington, 

 D. C, killing every 'worm' which came under the writer's observation."' 



•Circular No. 60, Bureau of Entomology, U. S. Dcpt. Agr. 



