[161] NOTES ON PIERIS OLERACEA. 29 



the preceding afternoon when they were not observed. The length of 

 the smallest was .23 of an inch. They now showed numerous dark 

 colored dots, which were more contiguous on the dorsal region, where 

 they define a vascular line of pale green. 



August 31st, A. M., the first of the six larvae now remaining, molted for 

 the third time ; its length, after its change was .31 of an inch. A 

 second one molted in the afternoon of the same day, and the four 

 others, by noon of the day following, September 1st. 



On September 3d, A. M., the first of the larvae molted for the fourth 

 and last time, when it measured .45 of an inch ; three were in position 

 for molting, which occurred on the following day. 



On the 7th two of the larvae suspended themselves for their pupal 

 change, and the other three (one having died) on the morning of the 

 8th. Later in the day they had all changed to pupae. On the 15th 

 the first imago emerged, a second on the 18th, and of the others no 

 note was made. 



The transformations of the butterflies of this brood are completed in 

 remarkably short periods of time. The intervals between the hatching 

 of the egg and the first molting, and that between the two following 

 moltings, are each but two days, and a period of three days carries it to 

 its last molt. Thence to its pupal change requires but five days, and 

 the brief space of seven days suffices for converting the pupa into 

 the perfect insect. The entire conversion of the egg into the imago 

 is effected in the space of three weeks. I have elsewhere shown 

 (Proc. Ent. Soc. Ph., vol. iii, p. 52), that there are at least three annual 

 broods of P. oleracea, viz., the last of April, the early part of July, 

 and last of August. In favorable seasons, a fourth apparition may 

 be added to the above, in the latter part of September. From the 

 observations recorded below, it is possible that this last appearance is 

 but a portion of the spring brood brought forth by an unusually warm 

 autumn. 



On the 19th of September I obtained, from the same small bed of 

 turnips from which the former collection of eggs was made, fifty-three 

 P. oleracea larvae, most of which were nearly of full size. By the 

 25th, all had transformed to pupae, and on the 27th one made its 

 appearance as an imago. During the following two weeks several 

 others emerged. Some weeks having passed without further develop 

 ments, the box containing the pupae was removed to a cold room for 

 the winter. In early March it was returned to a warm apartment, and 

 on the 6th of April an imago was disclosed, and others continued to 

 appear during the remainder of the month. It was observed that all 

 those given out during the first week were of the male sex. 

 [Assem. No. 133.] 21 



