128 



THE STUDY OF INSECTS 



Fig. 211. 



destitute of jointed legs. The pupae have the partially developed elytra, 

 wings, and legs folded upon the breast, but in distinct sheaths (Fig. 211). 

 These insects usually transform in rude cocoons made of earth or 

 of bits of wood fastened together by a viscid substance excreted 

 by the larvae. Many wood-burrowing species transform in the 

 tunnels made by the larvae; and some of the dermestids as well 

 as some of the lady-bugs transform in the last larval skin. 



Both larvae and adults present a very wide range of habits. 

 While the majority of the species are terrestrial, the members of 

 several families are aquatic; and while some feed on vegetable 

 matter, others feed upon animal matter. The vegetable feeders 

 include those that eat the living parts of plants, those that bore in dead 

 wood, and those that feed upon decaying vegetable substances. Among 

 the animal feeders are those that are predacious, those that feed on dried 

 parts of animals, and those that act as scavengers, feeding on decaying 

 animal matter. Viewed from the human standpoint, some species are 

 very beneficial, others are extremely noxious. 



In the classification of beetles much use is being made of the varia- 

 tions in form of the ventral and lateral sclerites of the thorax. Figure 

 215 will serve as an illustration of these sclerites. One feature merits 

 special mention: the coxae of the hind legs are flattened and immovably 

 attached to the thorax so that they appear to be a part of the thorax 

 instead of the basal segment of an appendage. 



The Coleoptera is a very large order, the latest catalogue listing 

 18,547 species representing 109 families. The order is divided into two 

 suborders, the Adephaga and the Polyphaga. 



CLASSIFICATION OF THE COLEOPTERA 



In order to use the table for determining the families of beetles it is 

 necessary that the student should become familiar with certain terms not 

 defined in the discussion of the external anatomy of insects. The follow- 

 ing notes are therefore given as a supplement to that discussion. 



The head. — One of the sclerites that enters into the 

 composition of the external wall of the head is frequently 

 referred to in descriptions of beetles; this is the gula. 

 The gula is the central portion of the ventral wall of the 

 head, and is the part which bears the labium (Fig. 212, g). 



The sutures which bound the 

 gula, one on each side, are 

 termed the gular sutures (Fig. 

 2 1 2 , gs) . In the Rhynchop- 

 hora the gula appears to be 

 wanting, and there is a single 

 suture on the middle line of 

 the head (Fig. 213, gs.) 



The antenna. — The 

 more common types of an- 

 tennae have been described. 

 In many insects however, (£ r ^ t J s e ' s c 

 the first segment of the an- 

 tenna is long and the an- 

 tenna is bent suddenly at the joint between the first and second seg 

 ments; such antennae are said to be elbowed or geniculate. 





Fig. 212. — Head of Ilarpalus, ventral 

 aspect: a, antenna; g, g, gula; ga, galea 

 or outer lobe of the maxilla; gs, gular 

 suture; //>, labial palpus; m, m, mandibles; 

 mp, maxillary palpus; s, submentum. 



Fig. 213. — Head and 

 prothorax of Rhyn, lio- 



proster- 

 em, epimerum; 



/, femur. 



