14 
THE PAN-PACIFIC ENTOMOLOGIST 
SCIENTIFIC NOTE 
Notes on the Larval Habits of Asemum caseyi Linsley and A. nitidum LeConte (Co- 
leoptera: Cerambycidae) — Little has been published regarding the larval habits of 
Asemum caseyi Linsley and A. nitidum LeConte, two cerambycids common on the Pacific 
Coast of North America. Linsley (1957, Amer. Mus. Nov. 1828: 13-14; 1962, The Ceramby¬ 
cidae of N. Amer. Pt. II, Univ. Calif. Pub. Entomol. 19:82-83) provides the only information 
on A. caseyi, listing four species of Pinus attacked and stating simply that the habits of A. 
caseyi “are similar to those of A. nitidum LeConte.” The habits of the latter are summarized 
(Linsley 1962), “the larvae bore in the sapwood and heartwood and require one or two 
years to complete their development.” The only additional information to be gleaned from 
the literature are Hopkins’ (1902, Soc. Prom. Agr. Sci. Proc. 22d. Ann. Meet., p. 68) remarks 
that in Western Oregon and Washington A. nitidum is “a very common enemy of the 
Douglas spruce and western hemlock” and “the healed-over wounds in the living bark 
cause gum spot defects in the wood, and the trees die from successive attacks,” and 
Lange’s (1937, Pan-Pacific Entomol. 13:174) observation that the species was the most 
common cerambycid occurring on Jeffrey and ponderosa pines during a 1935 salvage 
operation in the Lassen National Forest of California. 
The following observations are presented to supplement those reviewed above. On 
June 19, 1977, nonteneral adults of A. nitidum were found in their pupal chambers in the 
sapwood of a 50 cm high standing stump of Pinus sp. at an elevation of about 850 m on the 
east slope of Mt. Hamilton, Santa Clara Co., California. This locality represents a minor 
range extension for A. nitidum since Linsley (1962, Fig. 31) shows the species occurring in 
the California coast ranges only to the north of San Francisco Bay. Although the tree had 
apparently been sawed down because it was largely dead, the stump had recently oozed 
sap from the saw cut and the bark was still tight on the portion not attacked by the bee¬ 
tles. Adults were taken from pupal chambers oriented parallel to the grain and lying from 
2 to 4 cm beneath the surface of the wood. Others lay yet deeper within the wood. Exit 
holes in the thick bark indicated that many adults had already emerged. Pupation occur¬ 
red in a head-up position and a short (4 to 6 cm) exit gallery, which was tightly packed with 
frass, proceeded obliquely upward from the top of each chamber to the surface of the 
wood. Most of the larval feeding apparently occurred deep within the trunk, since the 
workings beneath the bark were not extensive and galleries other than exit galleries were 
not found in the outer sapwood. 
In January, 1976, at an elevation of 1700 m on Mt. Gleason in the west San Gabriel 
Mountains of Los Angeles County, California, I encountered a large downed bigcone 
pine, Pinus coulteri D. Don, which had broken off a meter or so from its base. The tree had 
been dead long enough to allow cerambycid larvae, primarily Rhagium inquisitor (Lin¬ 
naeus), to mine extensively beneath the bark of the fallen trunk. Upon my return in March, 
1977, only a few adult cerambycid emergence holes were present and numerous larvae 
were still working. Larvae of what later proved to be Asemum caseyi were found construc¬ 
ting pupal chambers in the 2 cm thick bark. Galleries penetrating the sapwood to an un¬ 
determined depth and tightly packed with granular frass continued into the bark a few 
millimeters, then turned and ran parallel to the grain a short distance before widening into 
rather flattened pupal chambers lying parallel to the inner surface of the bark. An oblique 
exit gallery was subsequently made by each larva from one end of its pupal chamber to 
within a couple of millimeters of the outer surface. 
Infested bark was taken from Mt. Gleason and placed on a screened-in porch at an ele¬ 
vation of 300 m on the costal slope of the nearby Santa Monica Mountains where the 
mean daily temperatures were slightly higher than those on Mt. Gleason. Adult A. caseyi 
emerged from P. coulteri bark in late May and early June, 1977, and incidentally estab¬ 
lished a new host record forthe species. 
Given that A. caseyi and A. nitidum are sympatric throughout most of the major moun¬ 
tain ranges of California, it is reasonable to suppose that the slight differences in larval 
habits noted here serve to reduce competition between these congeners. — DURWARD 
D. SKILES, Institute of Geophysics and Planetary Physics, University of California Los Angeles, 
90024. 
The Pan-Pacific Entomologist 54:14. January 1978 
