1920] lilackman — New Specif s of Pifyophthont.i from Colorado S 



The material from which Pitijophthorus bassetti was bred con- 

 sists of several slabs taken from the base of an Engelmann spruce 

 near Pitkin, Colorado by Mr. R. O. Bassett, Jr., a former student. 

 These were received at Syracuse Nov. "23, 1915 and upon exami- 

 nation the bark was found to contain numerous living nearly full 

 grown larvne of a scolytid. Further examination yielded the dead 

 parent beetles and these proved to be an unknown species of 

 Pityophthorus. The slabs were placed in a breeding jar in the 

 laboratory and a considerable number of beetles emerged during 

 the first two weeks of December. Part of these were preserved 

 as specimens while the rest were left in the breeding jar and 

 several pieces of a freshly cut limb of balsam fir about 1 inch in 

 diameter were introduced. The adults readily entered not only 

 the fresh balsam, but also some reentered the slabs of Engelmann 

 spruce from which they had emerged — breeding in both. The new 

 second generation of adults emerged from these two hosts during 

 the summer of 1916 and many of them were still alive in September, 

 at which time also a few small larvse doubtless of a third generation 

 were found. It would appear that normally there is not more 

 than one generation per year. 



The bark on the Engelmann spruce in which the beetles originally 

 bred w as about i e of an inch thick, while that of the balsam limbs 

 to which the new brood readily transferred was only tV of an inch 

 thick. In the former the larva' worked nearly entirely in the 

 inner and middle bark usually not even grooving the sapwood while 

 in the latter the larval mines were excavated partly from the sap- 

 wood. Aside from this the engravings in the two are similar. 

 In their general characteristics the engraving is not unlike those of 

 other species of this genus. It consists of an entrance gallery lead- 

 ing diagonally upward and inward to the junction of bark and sap- 

 wood where it is expanded into an irregular nuptial chamber. 

 From this a variable number of egg-galleries branch off from all 

 sides, but these soon take a general longitudinal direction. In 

 number the egg-galleries vary from 4 to 9 and the average in 13 

 engravings in balsam fir is 6.9. The effect of this large proportion- 

 ate number of females to each male upon their relative fecundity 

 could not be determined satisfactorily because of the injuries to the 

 engravings by the numerous brood. 



The egg-galleries which have a general longitudinal direction are 



