550 Report of the Entomologists of the 



an average, a little more than one-fourth of an inch in length. 

 The general shape of one of the full size cases is shown at Plate 

 XLI, fig. 1. The full grown case-bearers feed readily on nearly 

 all parts of the leaves, usually leaving only the midribs un- 

 touched. Plate XLI, fig. 2, is from a photograph of a few mature 

 apple leaves partially devoured by the case-bearers. The fruit 

 ma}' also be injured by the caterpillars boring through the skin 

 and feeding on the tissue just beneath. This causes the young 

 apples to become more or less deformed, according to the extent 

 of the injury. 



The full grown caterpillars measure, on the average, a little 

 more than one-fifth of an inch in length. The body is light-yel- 

 low, varying to deeper shades, with dark-brown markings on the 

 thorax. The true legs are black. The head also is black with 

 a more or less distinct yellow median line. Like other caterpil- 

 lars, the pistol-case-bearers undoubtedly molt, probably several 

 times during their development, but this interesting operation 

 was not observed by us. 



Pupation. — During the middle of May many of the case-bearers 

 were observed migrating from the leaves to the twigs. Toward 

 the latter part of the month a majority of them had pupated. 

 Before pupating each caterpillar had fastened its case securely to 

 the bark of the twig. A network of silk was woven over the 

 anterior end of the case, so that if the case was forcibly removed 

 the occupant would not be exposed. Plate XLI, fig. 3, is from a 

 photograph of some of the cases as they appeared at this time. 

 Thus made secure, the caterpillars managed to turn around in 

 their cases so that their heads were in the opposite direction. 

 The transformation from the caterpillar to the pupa then took 

 place. The pupa is dark brown in color. Fig. 6 represents two 

 cases cut open longitudinally, showing the caterpillar and 

 pupa. 



The pupa stage probaly lasts from ten days to two weeks. We 

 observed the moths issuing June 22d and until June 26th. The 

 moths escape by means of a slit-like opening at the posterior end 

 of the case. 



