65 



The eggs are deposited from January to April, and hatch out in from 

 ten days to two weeks from the time they are deposited. As soon as 

 hatched the young worms begin to feed upon the tender leaves, and, 

 when disturbed, let themselves down and hang suspended in the air 

 by silken threads, after the manner of other span worms. They are 

 then of a blackish color, with a row of whitish spots along each side of 

 the body and a pair of smaller whitish spots on each side of the first 

 three sutures of the abdominal segments. They are furnished with 

 only five pairs of legs. When about five days old they cast the skin 

 for the first time, repeating the operation at the expiration of another 

 five days, and twice again at intervals of about three days apart, 

 there being four molts or castings of the skin before the worms trans- 

 form to pupae. 



One of the full-grown worms is shown enlarged in the accompanying 

 figure (40, a). The color is a light pinkish gray, varied with a darker 

 gray or purplish, or sometimes with black and yellow, but never marked 

 with distinct lines; the piliferous 

 spots are black or dark brown, and 

 the spiracles are orange yellow, 

 ringed with black and usually sit- 

 uated on a yellow spot. The worms 

 become full-grown in the latter 

 part of April or during the month 

 of May; they then enter the earth 

 to a depth of from 2 to 4 inches and 

 form small cells, but do not spin 

 cocoons. The change to the chry- 

 salis takes place shortly after the 

 cells are completed, and the chrys- 

 alids remain unchanged through- 

 out the entire summer and until early in the following year, when they 

 are changed into moths, which emerge from the ground from the tirst 

 week in January to the last week in March. The male moth is winged, 

 but the female is wingless and is so very different in appearance from the 

 male that no one not familiar with the facts in the case would e\ ei 

 pect that both belong to the same species. Both sexes are represented 

 in the accompanying illustration (fig. 41), where a represents the male 

 and b the female moth enlarged, the natural size being indicated by the 

 slender lines. The species was originally described from a male speci- 

 men. The discovery that the female is wingless will necessitate remov- 

 ing it from the genus Boarmia and locating it near Phigalia. 



This insect has thus far been found only in California and Oregon, 

 Besides attacking the leaves of the English walnut, the writer has 

 found these spanworms feeding upon the leaves of the apple, prune, 

 and oak (Quercus agrifolia). There is a strong probability that this 

 insect is a native of the Pacific Coast, where it originally ted upon the 

 8967— No. 7 5 



Fig. 40.— Boarmia plumiocraria : a, larva— twice 

 natural size; b, fifth and sixth segments, 

 view ; c, seventh segment, from ahove — more en- 

 larged (original). 



