INTRODUCTIOX. 



the second pair of legs; 

 Fig. 11. 



while the metanotum and mefasternum bear 

 respectively the posterior membranous pair 

 of wings, and the hind legs : each of the 

 three under portions of the thorax, the pro-, 

 meso- and meta-sternum, is composed of 

 three parts, the central portion called the 

 sternum and two lateral pieces, the anterior 

 of Avhich is called the ejnsternum, and the 

 posterior the epimeroii ; these latter are very 

 variable in size, and are seldom all visible 

 any 



Prosternum of thorax of 

 D. marginalis. 

 a. Sternum (ending in ]iro- 

 sternal process), b S.Episterua. 

 c c. Epimera. d. Coxa. e. Tro- 

 chanter, f. Femur, g. Tibia. 

 h. Tarsus (5-jointed). 



m any one 

 sect ; both 

 epi.sterna 

 epimera of 



m- 

 the 



and 

 the 



Fig. 12. 



meso- and meta- 

 sternum are often 

 more or less hid- 

 den behind the 

 reflexed portions 



of the elytra called the e^pipleurm : those of 



the prosternum are also often hard to trace, 



the episterna especially being very small and 



sometimes invisible. 



The legs are six in number, and are 



attached to the body by a joint called the 



coxa, Avhich forms with the coxal cavity a 



ball and socket joint ; these coxal cavities, 



sometimes called acetalmla, are either en- 

 tirely closed in front or behind by the 



corneous substance of one or other of the 



sterna, or are j^artially closed by one and 



partially by another ; in the former case 



they are said to be closed behind, in the ^- Mesothorax oi^D.marginalis 



latter to be open behind : this character is 



of great importance in some families, as is 



also the relation of the position of the 



epimera to the coxal cavities : on the outer 



side of the anterior and middle coxee an 



additional piece, not connected witli the legs, 



may be observed; sometimes it is soldered 



to the coxaj, sometimes independently mova- 

 ble : this i^iece is called the trochantin, but 



a better name for it would be the jiaracoxa, 



as the term trochantin is sometimes used 



by continental writers as synonymous with 



trochanter ; the latter term, however, has nothing to do with the former, 



the trochanter being a small and somewhat variable piece which is joined 



seen vertie;illy. 

 /. Mesouotum (bearing elytra). 

 g^. Base of elytron, g". Apex of 

 ditto, g^. Lateral margin of 

 ditto. g"^. Suture of ditto. 

 g''. Disc of ditto, h. Winglet or 

 alula (covering or a continua- 

 tion of the mesothoracic spi- 

 racle), a b c. Sternum, epi- 

 sterna, and epimera of meso- 

 sternum (bearing middle legs). 



d. Coxa. e. Trochanter. 



B. Mesothorax seen from above. 



a. Scutellum. 



