THE LARCH CASE-BEARER 51 



After making their winter cases the larvae feed for three or four weeks 

 before entering hibernation. They migrate from the leaves in normal 

 seasons during the latter part of October. 



The larvae during this period of their lives may attack more than one 

 leaf. One would infer from Ratzeburg that as soon as the larva emerges 

 in September from its summer mine it builds its winter case and goes 

 into hibernation without more injury. Cecconi points out that in Italy 

 the larva feeds on the leaves before going into hibernation, and may mine 

 quite thoroughly more than one leaf after having made its winter case. 

 There is undoubtedly considerable injury done by the larvae at this period 

 of their lives. The leaves of the larch are, however, so large and so abun- 

 dant that this injury does not become conspicuous as a usual thing. 



Number of broods 



As the life history just detailed indicates, there is but one brood in a 

 year. This is similar to the life history of the cigar case-bearer and of 

 the pistol case-bearer on apples. 



NATURAL ENEMIES 



The larch case-bearer is subject to the attacks of a number of parasites, 

 especially in Europe. Two or three parasites have been bred at this 

 station, but not in large numbers. As yet, not enough material has been 

 obtained for determination. J. C. Crawford very kindly examined the 

 few that were obtained here, but could place them only provisionally 

 until he had more specimens for examination. He says, " One is a species 

 of Pteromalidae, apparently belonging to the tribe Pteromalini ;' the second 

 is a species of the genus Pachyneuron ; the third is a Tetrastichine and prob- 

 ably of the genus Tetrastichus." 



The following parasites are recorded as having been bred from this 

 insect in Europe; Bracon guttiger Wesm., Microdus pumilus Ratz., Campo- 

 plex nanus Gr., Anaphes(?), Entedon arcuatus Frst., Entedon laricinellae 

 Ratz., Pteromalus laricinellae Ratz., Campoplex tumidulus Gr., and Campo- 

 plex virginalis Gr. 



METHODS OF CONTROL 



No practicable method of control is known for this case-bearer on forest 

 trees over large areas. It can be controlled, however, on trees used for 

 ornamental purposes. An account is given below of experiments at this 

 station with arsenate of lead and the lime-sulfur solution. The concen- 

 trated lime-sulfur solution, diluted at winter strengths, proved very effec- 

 tive in killing the case-bearers while in hibernation. 



