THE ALFALFA LOOPEE IN PACIFIC NOKTHWEST. Ill 



Early in June the young larvae become numerous in the fields, 

 walking very much as do geometrid larvae or " measuring worms." 

 This is due to the fact that the larvae have prolegs on only the fifth, 

 sixth, and ninth abdominal segments. If disturbed they curl up 

 and drop to the ground, the older larvae lying there tightly curled 

 up and refusing to move when irritated, but larvae of the second and 

 third instars when touched alternately straighten out and curl up 

 very suddenly, thus jumping about spasmodically. The larvae while 

 young feed upon the epidermis of the leaves, skeletonizing them and 

 giving to the attacked plant a brownish appearance. The older 

 larvae — that is, after the third molt — eat from the edge of the leaf 

 toward the midrib, entirely consuming the leaves. The larval period 

 lasts about two weeks, there being five molts with periods of about 

 three days elapsing between each. When ready to pupate the larva 

 spins a loose white silken cocoon (PL XI, fig. 2) among a number of 

 leaves, usually well up in the plants, incorporating two or three 

 leaves in its structure. The larva completes the cocoon in about half 

 a day and, at least in the case of specimens reared in our insectary, 

 pupates the day following that on which the cocoon is completed. 

 The length of the pupal stage of specimens reared in our laboratory 

 was very uniformly 10 or 11 days. Dr. H. G. Dyar 1 gives 12 days 

 as the length of this period, and Mr. Koebele 2 records the length of 

 the pupal stage as from 10 to 15 days. He gives an exact rearing 

 record 3 wherein he mentions a larva collected at Piedmont, Cal., 

 February 24, 1888, which pupated on March 5, the moth emerging 

 March 22, making a pupal period of 17 days. Dr. F. H. Chittenden, 

 of this bureau, gives from 6 to 22 days as the pupal period of a 

 closely related species, Autographa hrassicce. 



Thus the time elapsing from egg laying until the adult emerges 

 covers a period of from 26 to 48 days, probably being about 30 days 

 in the Palouse country of Washington. 



The first adults of the second generation appear in early July, 

 and adults continue quite numerous throughout this month, belated 

 individuals having been collected as late as August 3. There are 

 two generations, and probably three in the case of the earlier ap- 

 pearing individuals, and larvae in all instars are to be found in the 

 field as late as the end of August, but these very late larvae probably 

 succumb during the winter. 



Mr. T. H. Parks, of this office, records finding the larvae of this 

 species about half grown in the alfalfa fields about Salt Lake City, 

 Utah, as early as May 22, in 1911. Larvae were found throughout 

 June. The first pupa found in this locality was obtained on June 5 



1 Entomologica Americana, vol. 6, p. 14, 1890. 



2 Bureau of Entomology Notes, No. 95 K. 



8 Bureau of Entomology Notes, No. 389 K. 



