( Ixiii ) 



at the n]ippr end of the mesial siitnre. The i)eristernam (pi'.it) is always 

 enbvertical, as iu other Lepidoptera, with the exce[)ti(Mi of the higher Kliopa- 

 locera {Poji/l/'on/i/in', Pieridae, Ni/mphalidac, and some Kri/ciiiiildc), in which 

 it is a transverse belt, and in which the sternnra has assnmed a jientagonal 

 shape. It is large in Sphingidae, and remains broad at the obli(jnely truncate 

 upper end, where it leans against the parasternuin ( jiaxf). This is a large plate, 

 extending obliqnely dorsad and mesiad from the meral suture (sm//, PI. LXIII. 

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

 connecting meso- and prothorax. The plate is angidate behind at its upper 

 corner. It is large in Hesjjci'iidae and all lleterocera, and always small in the 

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

 Below the parasternum we find the episternnm {est), witii which are fused tlie 

 hyposternum {Jii/M) and the marginal stripes along the coxal cavity. The 

 snture between episternnm and sternum is distinct, while it becomes occasionally 

 olisolete at the upper end near tjie parasternum, where it separates the 

 episternnm from the peristernnm. The episternnm is always ol)li(piely truncate, 

 with the nj)per inner angle more or less pointed, owing to the large development 

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

 it is quite different in sliape, the mesosternite of a Butterfly being alwaj-s 

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

 episternnm. In Hphhiqidm' and several other families of lleterocera sternum 

 and episternnm are sejiarated, while the latter and the hyposternum are merged 

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

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

 is possibly of value in the examination of the true phylogenetic connection 

 between the families of lleterocera. 



The division of the meral half of the sternite into plates, some of which 

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

 1*1. LXIII. f. 1. ',', which are representations of the breast in a lateral aspect. 

 The meral suture is more heavily drawn in these sketches than the other 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 jiaramernm (pam), corresjionding to the j)arasternum, and 

 the protomerum {/'rmj, corresponding to the steriuim. The area behind these 

 two plates is occupied by the large epimerum (epiii), corres])onding to the 

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

 which often vanishes behind, a marginal stripe ('/ip), situated along the meral 

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

 vertical suture into a small fiontal piece and a large posterior stri])e. The 

 epimerum becomes membranaceous above. In this membranaceous area, between 

 forewing and ejjisternal i)late, we observe a curved stripe of ciiitin, serving 

 most likely as a kind of spring. 



The metasternite is more simplified than the mesosternite. The episternum 

 and ('(linii'mni arc the only large plates ; the other plates are more or less 



