320 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Ait. ; Dr. Roland Thaxter tells me that it is also sometimes found on B. 
papyifera Marshall). This species of Thymalus is entirely North Ameri- 
can, so far as recorded, being found within, and limited to, the regions 
occupied by these species of white birch. The localities recorded are 
Canada, Maine, New Hampshire, Vermont, Massachusetts, New York, 
Pennsylvania, New Jersey, Michigan, Wisconsin, and Jowa. 
The only account of its life history is that of Beutenmueller (90), 
who gives little more than an accurate description of the larva and pupa. 
My specimens agree with his in every particular, excepting in regard to 
the size of the larva. He states that the larvae are 6 mm. by 3 mm., 
whereas my specimens of full grown larvae are not as broad, being only 
2~2.5 mm. broad by 6-7 mm. long. Material has been obtained in the 
spring from three localities about Cambridge; viz., Middlesex Fells, 
Arlington Heights, and Belmont. The eggs are deposited in the fall and 
hatch in the spring. Young larvae, 2-5 mm. long, were found in the 
fungi as early as the 17th of April, 1901, and the 4th of April, 1902. 
The larvae grow rapidly, bore through the fungus in various directions, 
and finally excavate a chamber at the end of the burrow, in which to 
pupate. These chambers are usually made in the upper portion of the 
fungus. A drawing of a resting larva, taken from one of the chambers 
is shown in Figure 6 (Plate 2). Peculiar hooked hairs are found on the 
under side of the abdomen, as shown in the drawing. These hairs are 
found on all of the older larvae, but not on the younger ones (2-4 mm. 
long), nor on the pupae. Inasmuch as the points of the hooks are 
turned forward, it seems as if these hairs would seriously impede the 
forward locomotion of the larvae. However, this would probably not 
be a great hinderance to the larvae, since they move but a few inches 
during the month or more of their existence. No use for these hairs 
can be suggested until further knowledge of the habits of the larvae is 
obtained. 
The first pupa from the larvae obtained April 17, 1901, appeared May 
9th. These larvae, kept in a laboratory where the temperature was from 
15°-22° C., had all pupated by the 13th of May. A drawing of one of 
the pupae is shown in Figure 8 (Plate 3). These pupae took from 8-10 
days to mature, the first imago appearing May 19th. There is consider- 
able variation in the date of the appearance of the imagines of this 
species, as larvae were obtained out of doors on May 29th. These did 
not begin to pupate till June 4th. The first of the beetles appeared in the 
imaginal state June 11th, while several did not appear until a few days 
later. It is probable that the beetles appear normally about the first of 
