CERAMBYCID^; 221 



showing that it is a true dimorphism and not mere variability, as 

 ordinarily conceived. This dimorphism also pervades Leptacm&ops, 

 with a few notable exceptions, such as falsa, but is not so evident 

 in the true Acmceops, such forms as discoidea and directa, being 

 remarkably constant in coloration. It is a singular condition, where 

 some species are subject to radical dimorphism and others, evidently 

 congeneric, are absolutely constant within the narrowest limits; it 

 simply indicates what may some day be recognized as subgeneric 

 groups within the genus. 



Prothorax rather acutely and abruptly though not strongly tuberculate 

 at the sides; body very deep black throughout, the elytral punctures 

 coarse 2 



Prothorax with the sides very feebly, obtusely prominent and rounded 

 invariably before the middle and just behind the apical constriction, 

 which is always large, deep and very evident; elytra never deep 

 black and very moderately sculptured, almost always with more or 

 less blue, greenish or aeneous coloration 3 



Prothorax as in the preceding group but having the lateral prominence 

 virtually wanting; body otherwise as in section 3 19 



2 Form stout, oblong, rather convex, shining, deep black, the elytra 

 more blue-black than the anterior parts; upper surface glabrous, the 

 under with a few small scattered hairs, the legs and first five antennal 

 joints with short and close-set stiff hairs, the remainder of the an- 

 tennae minutely, very densely puberulent and dull, the fifth joint 

 claviform, with an elongate opaque spot on the under surface in 

 nearly apical half; head densely and moderately punctured, the 

 tempora converging and arcuate behind the eyes; antennae (cf) 

 extending to apical third of the elytra, the third joint longer than 

 the fourth but shorter than the fifth; prothorax wider than long, 

 evenly convex, with small but strong scattered punctures, the median 

 line in part finely striate; scutellum nude and shining, elongate, 

 acutely ogival; elytra parallel, not quite twice as long as wide, three 

 and one-half times as long as the prothorax and three-fourths wider, 

 rounded at apex, parallel, the sutural angle right but blunt; punc- 

 tures coarse, irregular, in part somewhat confluent transversely 

 but generally widely separated; abdomen minutely, sparsely punc- 

 tate. Length (cf 1 ) S.o mm.; width 3.0 mm. Washington State. 



atra Lee. 



Form not so stout, convex, intense black throughout, glabrous above, 

 the small sparse hairs of the under surface so minute as to be barely 

 discoverable; legs with sparse and very minute hairs; head and 

 prothorax strongly, densely, subrugosely punctate, the front de- 

 pressed between the antennae and the eyes; antennae (9) thick, 

 not extending to the middle of the elytra, the third joint shorter than 

 the fourth and two-thirds as long as the fifth; sides only very feebly 

 converging but strongly arcuate between the eyes and the base; 

 prothorax very short, one-half wider than long, much narrowed but 



