COLEOPTERA. 39 



trunk. On each side of the rostrum there is usually a groove into 

 which the long first joint of the antennae generally lies when the 

 insect is at rest. These grooves are called scrobes, and are useful 

 characters in the determination of the Ehynchophora. The anterior 

 portion of the head is called the forehead or front, and the central 

 portion the vertex. 



The antenna- are very variable in the Coleoptera, and in many 

 cases afford good points for the discrimination of genera and 

 species. The eyes are generally very prominent. 



The thorax, of course, can be easily recognised, but it must be 

 remembered that the transverse division line as seen from the upper 

 surface does not represent the length of this segment, inasmuch as 

 it projects on the under surface and extends under the abdomen. 

 In other words, the under side of the thorax projects beyond the 

 apparent divisional line, and the anterior portion of the abdomen 

 therefore rests upon the thorax. 



It is of importance to well understand the structure of the thorax, 

 more especially in the case of Scolytidae or "bark -beetles." The 

 thorax proper is made up of three parts the prothorax, mesothorax, 

 and metathorax ; and here again we must study the upper and under 

 surfaces of those divisions. In the upper surface these divisions are 

 known as -pronotum, mesonotum, and metanotum, and the under 

 surfaces the prosternum, mesosternum, and metasternum. As regards 

 the upper surface, the visible portion of the mesonotum is known as 

 the scutellum, which is a small but important triangular space, 

 wedged in, as it were, between the elytra and thorax. From the 

 under surface of the thorax we get the legs, and from the upper the 

 elytra and wings. 



The abdomen does not, as a rule, present many important features, 

 either as to external anatomy or as to points of classification. The last 

 segment or pygidium is rather important, inasmuch as it contains the 

 organs of reproduction. The legs spring from the thorax, and are 

 attached to the body by a joint called the coxa. The next joint is a 

 very small portion known as the paracoxa (Fowler), and attached to 

 this we have the strongest portion, known as the femur. The next 

 portion is the tibia ; and the last division is a most important one 

 viz., the tarsus. ~Not only in beetles but in all orders the number of 

 joints forming the tarsus must be noted. In the Coleoptera we have 

 the whole family subdivided, according to the number of joints in 



