( Lxiii ) 



at the u]ipi'r end of the mesial suture. Tlie i)eristermiiu (pest) is always 

 snhvertical, as iu other Lepidoptera, witli the exception of the higher Rhopa- 

 locera {Pajjilioniilae, Pierulae, Ni/mphulidae, and some Eri/cinidae), in which 

 it is a transverse belt, and in which the sternum has assumed a pentagonal 

 shape. It is large in Sp/nngidae, and remains broad at the obliquely truncate 

 upper end, where it leans against the parasternum [past). This is a large plate, 

 extending obliquely dorsad and mesiad from the meral sutnre {smu, PL LXIII. 

 f. 1), separating the meral and sternal jiavts of the sternite, to the membrane 

 connecting mcso- and pvotiiorax. The ])late is angnlate behind at its upper 

 corner. It is large in llesperiidae and all Ileterocera, and always small in the 

 Bnttertlies. Between it and the notum the mesothoracic tegula {nitg) is inserted. 

 Below the parasternum we find the episternum {est), with which are fused the 

 hyposternum {hijst) and the marginal stripes along the coxal cavity. The 

 suture between episternum and sternum is distinct, wliile it becomes occasionally 

 obsolete at the upper end near the i)arasternum, where it separates the 

 episternum from the peristernum. The ei)isternnm is always obliquely truncate, 

 with the upper inner angle more or less pointed, owing to the large development 

 of the parasternum. In the Butterflies (except a portio.i of the llesperiidae) 

 it is quite different in shape, the mesosternite of a Butterfly being always 

 distinguishable from that of a Moth by the development of the para- and 

 episternum. In Spliiiigidue and several other families of Ileterocera sternum 

 and episternum are separated, wliile the latter and the hyposternum are merged 

 together. There is another group of families in which sternum and episternum 

 are fused, while the comparatively large hyposternum is free. This distinction 

 is possibly of value in tiie examination of the true {)hylogenetic connection 

 between tlie families of Ileterocera. 



Tlie division of tlie meral half of tlie sternite into plate.^, some of which 

 are visible also in a frontal view of the breast, will be understood by comparing 

 PI. LXIII. f 1. ;J, which are representations of the breast in a lateral asjiect. 

 The meral snture is more heavily drawn in these sketches than the otlier sutures, 

 in order to make the division into a meral and a sternal part more obvious. 

 Along the meral suture we find two more or less strongly convex plates, which 

 may be termed the iiaramerum {pani), corresi)onding to the parasternum, and 

 the protomerura {prin), corresponding to the sternum. The area beliind these 

 two plates is occupied by the large epimerum (epm), corresponding to the 

 episternum ; from the epimerum is separated by a more or less distinct suture, 

 wliich often vanishes behind, a marginal stripe (wp), situated along the meral 

 cavity (= jiosterior jiart of coxal cavity bearing tiie merum), and divided by a 

 vertical suture into a small fioutal piece and a large posterior stripe. The 

 epimerum becomes membranaceous above. Id this membranaceous area, between 

 fbrewing and episternal plate, we observe a curved stripe of chitin, serving 

 most likely as a kind of spring. 



The metasternite is more simplified than the mesosternite. The episternum 

 and epimerum are the only large plates ; the other plates are more or less 



