BEETLES. 337 



making passages out from it. The eggs are laid singly in separate niches, which the 

 females gnaw out at regular intervals along the sides of these radiating passages. 

 According to Lindemann, if only one female comes to the male in his copulation- 

 chamber, then only one radiating passage is made along which to lay eggs, but if more 

 than one female comes to the same male, then each female makes a radiating passage 

 from the single copulation-chamber. Each larva, when it hatches, eats out more or 

 less at right angles to the radiating passages, increasing the size of its mine to accom- 

 modate its increased growth. The different larvae, all boring out from a common 

 centre or channel, each species in a way peculiar to itself, produce remarkable foliate 

 or. dendriform figures, which are modified by the number of radiating channels, a 

 number dependent ujDon the number of females that came to the male which origin- 

 ally established the colony. 



The larv£e of Scolytidse are legless, cylindrical grubs ; locomotion is effected by 

 fleshy warts which replace the legs. These larvse have no ocelli, and very short con- 

 cealed antennae; they pupate beneath bark or concealed in plants, and thus their 

 whole transformations are undergone out of reach of all birds except woodpeckers, 

 The beetles themselves are nocturnal, thus escaping insectivorous birds. Besides the 

 wood-boring habits of the Scolytidse, which render them especially destructive to 

 forests, the iinagos of some species eat the buds of conifers to such an extent as to 

 kill the trees. Some entomological writers, however, claim that the Scolytidae attack 

 only dead or dying trees. The North American Scolytidas number about one hundred 

 and forty described species, of which the specific characters are minute, 

 and of which only a few of the best-known species need be mentioned 

 here. 



The species of Dendroctmius are rather large, cylindrical, with 

 five joints in the funicle of the antennae, that is, in the portion be- 

 tween the basal joint, — often called the scape, — and the club or 

 dilated end of the antennae. D. terebrans, a species about 0.3 of an .„ 



. ^ Fig. 377. — Deii- 



inoh long, and common throughout the United States and Canada, droctmus tere- 

 feeds in pine. Hylurgus piniperda, a nearly allied species, attack- 

 ing all kinds of pine in Europe, possesses, in both sexes, sonorific apparatus, consist- 

 ing of two corrugated organs on the abdominal segments, which produce noise by 

 rubbing against corresponding portions of the elytra. 



Hylesinus includes species in which the funicle of the antennae is composed of 

 seven joints, and nearly or quite equals the club in length. Most of the species are 

 clothed with flat scales. H. trifolii, a species that, in Europe, has done much damage 

 by boring in the roots of clover and medic {Medicago sativa), has been found in the 

 eastern United States seriously injuring the clover crops. The beetles are about 0.1 

 of an inch long. They pair in early spring, and, after pairing, the female gnaws a 

 cavity in the top of roots of two-years-old clover, wherein she deposits from four to 

 six white elliptical eggs. The larvae, as soon as they are hatched, bore along the axes 

 of the roots of the clover, causing the plants to weaken, and often to die. Sometimes 

 as many as sixteen specimens are taken in a single clover root. Hybernation takes 

 place as larva, pupa, or imago. No mode of successfully combating this enemy of 

 clover crops has been devised. A number of European species of Hylesinus attack 

 pine, others, ash, poplar, or ivy {Hedera helix). H. aculeatus, of North America, 

 depredates on ash. 



In Scolytns, " the side margin of the prothorax is distinctly defined, a very rare 

 VOL. ir. — 22 



