116 MISCELLANEOUS FOREST INSECTS. 



angle. As stated by Reitter, later by Casey, and as is easily seen, they 

 are produced and in some species as strongly as in any true Lyctus. 

 Reitter in his synopsis states that in Trogoxijlon the sides of the head 

 are provided with three hooklike teeth, that the pronotum has all its 

 angles sharp, and that the elytra arc without rows of punctures or 

 hairs, but that these are irregularly disposed. As a matter of fact, 

 Lyctus (Trogoxylon) impressus Comolli does have the three elevations 

 mentioned, but in all the species so far recognized in the United States 

 not only the tooth over the eye is obsolete, but the posterior angles 

 and margin of the epistoma are closely joined to the angles of the 

 front, so that the epistoma is but slightly depressed below the level 

 of the front, and the two elevations seen in many species of Lyctus 

 are not traceable — a character also observable in L. (Xylotrogus) 

 politus n. sp. The shape of the pronotum is of little value; in L. 

 hrunneus Stephens all the angles are acute. The elytral punctures in 

 L. (Trogoxylon) californicus Casey are decidedly striate and there is 

 a tendency to the same thing in L. curtulus Casey. 



The first visible ventral segment in most species which would fall 

 in Trogoxylon is as long as the second and third combined, but in 

 others it is not longer than the second and one-half of the third. 



Xylotrogus has long since been shown by Wollaston (1854) and 

 other writers to be synonymous with Lyctus, and Trogoxylon must 

 also be so considered, though it might well be regarded as repre- 

 senting a well-marked subgenus. 



The species of the family Lyctidse are very variable, especially in 

 size. Well-developed individuals are frequently four or five times 

 larger than others, the difference in size perhaps depending largely 

 on food supply; for the offspring of those individuals which have 

 bred in the same piece of wood for four, five, or six generations are 

 very much smaller and quite different in some of the structural 

 details from the first individuals reared. Accompanying the decrease 

 in size are found such changes as in the shape and punctation of the 

 pronotum and the punctation and pubescence of the elytra. As a 

 result, one must allow for much variation within the limits of the 

 species, and characters which might be of specific importance in 

 groups more constant in character can only be held to be individual. 



SYNOPSIS OF SPECIES OF THE GENUS LYCTUS. 



Elytral pubescence confused over the entire surface or sometimes in single rows, 

 never in double series separated by wide intervals; apical angles of the prothorax 

 usually decidedly prominent — if not, at least subprominent and the sides of 

 pronotum decidedly convergent posteriorly Division I, pages 117-119. 



Elytral pubescence always arranged in distinct series, the series at the sides at least 

 separated by a double row of fine, deep punctures or a single row of large, shallow, 

 circular punctures Division II, pages 119-120. 



