ss 



TEXT-BOOK OF ENTOMOLOGY 



epm 



- epm 



tr te' c" tr c'" tr 



ptm 



FIG. 90. Thorax of Teleft polyphemu<s, side view, 

 pronotum not represented: em, epimerum of prothorax, 

 the narrow piece above being the prothoracic episternum; 

 ms, mesoscutuni ; su/n, mesoscutellum ; ntx", metas- 

 cutum ; t)em'", inetascutellum ; pt, a supplementary 

 piece near the insertion of tegula? ; ', pieces situated at 

 the insertion of the wings, and surrounded by mem- 

 brane ; epm", episternum of the mesothorax ; em", 

 epiinerum of the same; epm'", episternum of the 

 metathorax ; em'", epiinerum of the same, divided into 

 two pieces; c', c", c'", coxie ; te', te", te'", trochan- 

 tines ; tr, t>: tr, trochanters. A, tergal view of the 

 mesothorax of the same ; j'm, prieseutum ; m*, scu- 

 tum ; scm, scutellum ; ptm, postscutellum ; t, tegula. 



form the base of attachment. The scutum is invariably present, as 

 is the scutellum. The former in nearly all insects constitutes the 

 larger part of the tergum, while the latter is, as its name implies, the 



small shield-shaped piece 

 directly behind the scutum. 

 The prsescutum and post- 

 scutellum are usually mi- 

 nute and crowded down out 

 of sight between the oppos- 

 ing segments. As seen in 

 Fig. 90, the prsescutum of 

 most moths (Telea) is a 

 small rounded piece, bent 

 vertically down so as not 

 to be seen from above. In 

 Polystoechotes and also in 

 Hepialus the prsescutum is 

 large, well-developed, tri- 

 angular, and wedged in 

 between the two halves of 

 the scutum. The postscutellum is still smaller, usually forming a 

 transverse ridge, and is rarely used in taxonomy. 



The metathorax is usually smaller and shorter than the mesotho- 

 rax, being proportioned to 

 the size of the wings. In 

 certain Neuroptera and in 

 Hepialidae and some tin- 

 eoid moths, where the 

 hind wings are nearly as 

 large as those of the 

 anterior pair, the meta- 

 thorax is more than half 

 or nearly two-thirds as 

 large as the mesothorax. 

 In Hepialidse the pra?scu- 

 tum is large and distinct, 

 while the scutum is di- 

 vided into two widely 

 separated pieces. The 

 postscutellum is nearly or quite obsolete. 



The pleurum in each of the three thoracic segments is divided 

 into two pieces ; the one in front is called the episternum, since it 



tr" 



FIG. 91. Thorax of the house-fly: j'n, pronotum 

 prxi 1 , pnesciitiini ; ', niesoscutum ; /', inesoscutelhim 

 jixcf, postscutellum ; a/, insertion of sijuaina. extending 

 to the insertion of the wings, which have been removed 

 tnn/i/ir, iiu'sophragma ; //. balancer (halter); pt, tegula 

 i>/tii, iiietiiiiotiim ; I'/II'M, ejn'x', c/i/.-,", e|pisternum of pro-, 

 nii'Mi . and meta-thorax ; rji/ti', cpi/i", niesu- and tneta- 

 ' " ' " 



xf, xf". nicso- and meta-sternuin ; <.;'. ex' 

 ; tr'. tr", tr'", trocliaiiters of the three pairs 

 of legs; x/i', x/i", up'", xp"", up'"", first to fifth spir- 

 acles; /(/', ft/", terirites of first and second abdominal 



