62 



interest rather than of economic importance, as the two species show 

 close similitude in the details which go to make up their life histories. 



DESCRIPTION OF THE SPECIES. 



The adult. — The adult or mature form of this insect is a snout- 

 beetle or curculio of the typical rhynchophorus family, Curculioni- 

 dse. It is one of the largest species of its kind, measuring from the 

 tip of its long snout about three-fourths of an inch in length and 

 is about three-sixteenths of an inch in width. The body and head 

 together are about five-eighths inch long and the snout nearly three- 

 eighths. The snout is cylindrical, black in color, and grooved on the 

 sides for the reception of the scape of the antennae. From other 

 related genera the species of Lixus may be distinguished by the polli- 

 nose substance with which their bodies are covered. The covering of 







d a e 



Fig. 15. — Lixus concavus: a, beetle; b, egg; c, newly hatched larva; d, full-grown larva; c, pupa in 

 profile, showing dorsal motorial spines; /, dorsal view of last abdominal segments of pupa— all about 

 twice natural size (original) . 



Lixus concavus is very bright yellow, and the writer has kept hiber- 

 nated specimens for two or three months that retained this pollinose 

 covering, which he considers pubescence. It readily rubs off, how- 

 ever, when the insect is handled. The elytra are of remarkably firm 

 consistence, so hard, in fact, that it is difficult to impale the beetle 

 with an ordinary insect pin. From other species of the genus, con- 

 cavus is to be distinguished by the deep triangular concavities at the 

 bases of the thorax and elytra. The prothorax is just perceptibly 

 wider than long, moderately rounded at the sides, and distinctly con- 

 stricted apically. . 



In the male the snout is shorter and the antenna? are inserted about 

 one-fourth from the apex, while in the female they are placed about 

 one-third from the end. The female is represented in figure 15 at a. 



Lixus mucidus, the only other species known to attack rhubarb, is 



