526 



^A^ INTRODUCTION TO ENTOMOLOGY 



Fig. 636. 



Fig. 637 



lated, and the third is either bilobed or not (Fig. 634, C). The seg- 

 ments of the antennae have deep impressions, in which are situated 

 the organs of special sense (Fig. 636). The 

 most common species is Pardndra hriinnea (Fig. 

 637) ; this insect is of a mahogany-brown color, 

 and measures from 9 mm. to 18 mm. in length. 

 The broad-necked prionus, Prionus laticollis. 

 — This is the largest of our common species; 

 but the individuals vary from 22 mm. to 50 mm. 

 in length. It is of a pitchy-black color, and of 

 the form shown in Figure 638. The antennas 

 are twelve-jointed in both sexes. The larva is 

 a large, fleshy grub, and infests the roots of grape, 

 apple, poplar, and other trees. 

 The tile-homed prionus, Prionus imhricornis, is very similar to 

 the preceding species but can be distinguished at a glance by the 



form of the antennse. In the antennae of 

 the male the number of segments 

 varies from eighteen to twenty, while in 

 the female the number varies from sixteen 

 to seventeen. The popular name refers 

 to the fact that the segments of the an- 

 tennae of the male overlap one another 

 like the tiles on a roof. The larva infests 

 the roots of grape and pear, and also feeds 

 upon the roots of herbaceous plants. 



The straight -bodied prionid, Dero- 

 brachus briinneus, is also a common spe- 

 cies. The body is long, narrow, and some- 

 what flattened ; it measures from 2 5 mm. 

 to 35 mm. in length, and is of a light 

 brown color. The prothorax is short, and 

 is armed on each side with three sharp 

 spines. The sides of the wing-covers are 

 very nearly parallel ; this suggests the common name. The adult flies 

 by night, and is often attracted to lights; the larva is supposed to 

 infest pine. 



Fig. 638. 



Subfamily CERAMBYCIN^ 



The Typical Ceranibycids 



In this subfamily the prothorax is rounded on the sides, the tibiae 

 of the fore legs are not grooved, and the palpi are never acute at the tip. 

 There are nearly four hundred American species, representing more 

 than one hundred genera. The few species mentioned below are those 

 that the beginning student is most likely to meet. 



The ribbed pine-borer, Rhdgium linedtum. — This is a gray beetle 

 mottled with black, and has a narrow thorax, with a spine on each 



