April, 1921] A New Ambrosia Beetle . 205> 



Xyloterinus politus Say. (Fig. 1(7, work in beech.) 



Very little seems to have been noted relative to the work 

 and burrows of this species. It has long been known that the 

 insect, like forms in the genera Gnathotrichus, Pterocylon, 

 Trypodendron, etc., rears its young in separate pits or cradles, 

 the cradles projecting in opposite direction at right angles to 

 the main passage way and with the fiber of the wood. 



The compound ambrosia tunnels of Gnathotrichus, Pterocylon, 

 Trypodendron, etc., have only two rows of larval cradles, one 

 projecting above and the other extending below^ the main egg- 

 gallery. The larval cradles of Xyloterinus politus (Fig. 1, b) are 

 double-compound or quadrifarious, i. e., arranged in double 

 rows or two on each side of the main passage way. Compound 

 ambrosia beetle tunnels should then be divided into two classes : 

 viz. (1) egg-galleries with only two rows of larval cradles, one 

 extending above and the other below the main passage way and 

 (2) egg-galleries with quadrifarious or tetrad-rows of larval 

 cradles, two projecting above and two below the main passage 

 way. 



The tetrad-rows of larval cradles of X. politus Say were first 

 observed by the writer while collecting Ipidse on the roll-way 

 described above. The insect seems to prefer beech for breeding 

 purposes, but it is also common in maple and frequently in 

 birch. Numerous other food plants have been recorded by 

 Hopkins (Bull. 33, W. Va. Agr. Exp. Stat., 1893, p. 210) and 

 Swaine (1. c, p. 83). The latter (1. c, p. 10) describes the peculiar 

 and characteristic projection of a cylindrical rod-like mass of 

 frass from the entrance hole while the insect is actively engaged 

 in excavation of its tunnels. Schwarz (Proc. Ent. Soc. Wash., 

 Vol. II, 1891, pp. 77-81) publishes notes on the breeding habits 

 of some scolytids, including this insect, but does not describe 

 the larval cradles. The writer examined over thirty different 

 galleries, in most cases on both sides, and found the larval 

 cradles of politus to be arranged in double rows on each side of 

 main passage way. All specimens of work of this insect exam- 

 ined or at hand are from the neighborhood of Cranberry Lake 

 in the Adirondacks. As the larval burrows have not yet been 

 described or figured by other w^orkers, who have published 

 on the insect, it is impossible to state whether the double-^ 

 compound larval cradles are a specific character peculiar to 

 this insect or whether it is a race or variety living in the vicinity^ 

 of Cranberry Lake, New York. 



