1919] Blackmail — Xoies on Species of Pityophthorus 135 



females, lingered near and apparently took no farther part in the 

 operations than occasionally to approach the working male and 

 stroke him with their fore-legs and antennae. 



Some of the more advanced burrows opened at this time con<- 

 tained only a single male in the still uncompleted nuptial chamber, 

 while in others the nuptial chamber was completed and occupied 

 by the male and from one to three females. Some of these were 

 preserved as specimens, while others were removed from their 

 burrows and placed in jars with fresh pine limbs, into which the 

 males immediately began burrowing. One of the new burrows 

 thus started was examined nine days later (May 3) and was found 

 to have three radiating egg-galleries containing eggs in the niches 

 along each side. Several eggs, removed and preserved, were 

 found to contain larvae, the mandibles of which showed brown 

 through the semi-transparent egg membranes. The remaining 

 eggs — doubtless several days younger — when examined on May 6 

 were still unhatched, but on May 9, larvae about one day old were 

 found. On June 4, numerous apparently full grown larvae and 

 several pupae were found although several of the parent adults 

 were still alive in their egg-galleries. 



Adults of the new generation emerged the following month dur- 

 ing the writer's absence from the laboratory*, and were numerous 

 in the jars on his return July 2. It is thus apparent that several 

 generations may occur during a single season and it seems probable 

 that two broods per year are the rule in central New York. How- 

 ever, this depends very largely on the temperature and moisture 

 conditions surrounding the particular branch in which the brood 

 occurs. If this lies in a cool, shady spot where the sun never pene- 

 trates, the life processes are slowed up to such an extent that only 

 one generation, or one and a half generations per year occur. In 

 September, 1916, several branches, obtained where such conditions 

 prevailed, contained young adults which from the character of 

 their feeding burrows had fed as adults since midsummer. In 

 other parts of the same woods, similar branches lying in places 

 where the sun reached them during part of the day, had been long 

 deserted by their brood and the feeding burrows showed that the 

 young adults had remained in them a comparatively short time. 

 The writer is certain that this difference is not entirely explained 

 by the lengthened egg, larval and pupal periods, but that we have 



