THE PAT AGFA AND TEGULsK 



89 



rests upon the sternum ; the other is the epimerum. To these pieces, 

 with the sternum in part, the legs are articulated (Fig. 89). 



Between the episterna is situated the breastplate or sternum, 

 which is very large in the more primitive forms, as the Orthoptera, 

 and is small in the Diptera and Hymenoptera. 



The episterna and epimera are in certain groups, Neuroptera, etc., 

 further subdivided each into two pieces (Fig. 102). The smaller 

 pieces, hinging upon each other and forming the attachments of the 

 muscles of flight, differ much in shape and size in insects of different 

 orders. The difference in shape and degree of differentiation of these 

 parts of the thorax is mentioned and illustrated under each order, 

 and reference to the figures will obviate pages of tedious description. 

 A glance, however, at the thorax of a moth, fly, or bee, where these 

 numerous pieces are agglutinated into a globular mass, will show 

 that the spherical shape of the thorax in these insects is due to the 

 enlargement of one part at the expense of another; the prothoracic 

 and metathoracic segments being more or less atrophied, while the 

 mesothorax is greatly enlarged to support the powerful muscles of * 

 flight, the fore wings being much larger than those appended to the 

 metathorax. In the Diptera, whose hinder 

 pair of wings are reduced to the condition of 

 halteres, the reduction of the metathorax 

 as well as prothorax is especially marked 

 (Fig. 91). 



The patagia. On each side of the pro- 

 notum of Lepidoptera are two transversely 

 oval, movable, concavo-convex, erectile plates, 

 called patagia (Fig. 92). On cutting those of 

 a dry Catocala in two, they will be seen to be 

 hollow. Cholodkowsky J states that they are 

 filled with blood and tracheal branches ; and 

 he went so far as to regard them as rudi- 

 mentary prothoracic wings, in which view he 

 was corrected by Haase, 2 who compares them 

 with the tegulse, regarding them also as secondary or accessory 

 structures. 



The tegulae. On the mesothorax are the tegulce of Kirby (ptery- 

 godes of Latreille, paraptera, of McLeay, hypoptdre or squamule), which 

 cover the base of the fore wings, and are especially developed in the 

 Lepidoptera (Fig. 90, A, t) and in certain Hymenoptera (Fig. 95, c). 



1 Cholodkowsky, Zool. Anz., ix, p. 615 ; x, p. 102. 

 2 Zool. Anz., ix, p. 711. 



FIG. 92. Prothorax of 

 Geometra papilionaria : 

 n, noturn ; j>, pleura ; fit, 

 sternum ; pt, patagia ; m, 

 membrane ; ./', femur ; h, a 

 hook bent backwards and 

 beneath, and connecting the 

 pro- with the mesothorax. 

 After Cholodkovsky. 



