THE IMPORTED CABBAGE WEB WORM. 35 



At Honolulu eggs have been observed to hatch in from two to three 

 days. Within a very short time after hatching the larvae endeavor 

 to conceal themselves. When very small cabbage plants in seed beds 

 are infested the larvae conceal themselves by folding a tender leaf 

 and fastening the edges together with a web. Rarely is more than 

 one larva found on a single leaf. With somewhat larger plants the 

 larvae mine into or crawl between the curled, terminal leaves at the 

 " bud,*" and, as they increase in size, burrow deeper into the main 

 stalk. When a plant is thus infested it is rendered worthless. ' With 

 large plants which are beginning to head the larvae mine into the mid- 

 ribs or live in burrows between two leaves. The chief damage is 

 caused by the larvae destroying the " buds " of the small to medium- 

 sized plants. When the " buds " of small plants in the seed bed are 

 attacked the plants may be killed outright. With larger plants the 

 destruction of the " bud " effectually prevents further normal develop- 

 ment. Rain falling into the burrows hastens decay, thus completing 

 the injury begun by the larvae. On Oahu the larvae are called " center 

 worms," from their habit of mining into the center or " bud " of 

 cabbage plants. 



The larvae usually reach maturity in from 13 to 15 days. They 

 then leave the plants, burrow slightly beneath the surface of the soil, 

 and form rather frail cocoons of webbed-together grains of earth, 

 within which they pupate within 2 days. During the progress of 

 these studies thousands of larvae were under close observation, and 

 they invariably burrowed into the soil and made cocoons of webbed- 

 together grains of earth. The adults usually issue in from 6 to 12 

 days after pupation. They fly easily, but are shy and are rarely 

 noticed by the casual observer. 



It is probable that this species breeds throughout the year in 

 Hawaii. Judging, however, from the reports of gardeners, it is evi- 

 dent that reproduction is at a low ebb during the cooler months. 

 This idea is borne out by the fact that the larvae were noticeably less 

 abundant at Wahiawa in late December and at Honolulu in January 

 than earlier in the season. 



Four generations of this webworm were reared in an insectary at 

 Honolulu. The record for the first generation is incomplete. 



FIRST GENERATION. 



September 2, 1910, several mature larvae were collected from cab- 

 bage in a garden at Honolulu and confined in a cage. They burrowed 

 into the soil September 3 and pupated September 5. The first moths, 

 4 in number, issued September 12, and the following day 8 more 

 issued. The 12 moths were then put in another cage, containing a 



