320 bulletin: museum of comparative zoology. 



Ait. ; Dr. Eoland Thaxter tells me that it is also sometimes found on B. 

 papyifera Marshall). This species of Tliymalus is entirely North Ameri- 

 can, so far as recorded, being found within, and limited to, the re^jions 

 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 Iowa. 



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, 

 ^ly specimens agi'ee Avith 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 aboxit Cambridge; viz., Middlesex Fells, 

 Arlington Heights, and Belmont. The eggs are deposited in the fall and 

 liatch 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 woidd 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 



