( hiv ) 



fused with them, the sternum heiii^r, however, always jjreserved as a narrow 

 separate strijjc. 



The coxa is inserted in a groove lormed by the sternal part of the 

 sternite ; it bears the trochanter {trocli), and is supported behind by the merum. 

 It will be observed from the figures that the midcoxa is much slenderer than 

 the merum, while tlie hindcoxa is larger than the respective merum. Tliere 

 is a very remarkalile sjiecialisation found in the merum. The hinder edge of 

 tlu' nienuii is normally rounded : but in I'dchylia, Nephele, and other genera 

 the edge becomes carinate and angulate ; in the higher Sesiinae and Pliilam- 

 pelinae. the angle assumes more and more the shajje of a sharp triangular 

 process, reaching the highest point of sjiecialisation in Cephonodes (PI. LXIII. 

 f. 2). The mesosternal merum shows this specialisation first, the metasternal 

 one slowly following. The processes project so far sideways that there is room 

 for tlu' femur between the process and the breast. The femur is generally found 

 in this j)osition. The object of this specialisation is doubtless to prevent the 

 legs and the incision between meso- and metathorax from being a hindrance 

 in the darting flight of the insects. This becomes quite evident when we 

 compare the abdomen, which is closely appressed to the breast in the forms 

 with strongly angulated merum, and liears very strong and flat spines, making 

 the abdomen very smooth. 



In the upper corner between coxa and merum we find the trochautinus 

 (tc/nn), a small plate which is more or less subglobose. The femora do not 

 offer any characteristic points. It is a curious fact, however, that they remain 

 always simple, even in cases where the tibia has become strongly spinose. 

 Tibia and tarsus undergo several modifications. Their relative length is often 

 variable either specifically or generically. A tibia clothed with scales and some 

 hairs, and truncate at the end, may be called a normal one. The apex of the 

 foretibia is often produced into a strong process (a thorn), which character is 

 sometimes of generic, sometimes only of specific value (PI. LXIV. f. 16). Such 

 a thorn is found here and there in all subfamilies (except Choerocampinae). It 

 is a specialisation often combined with other specialisations. It wonld, however, 

 be erroneous to say that a species possessing the thorn was in every respect 

 more specialised than the allied species which is devoid of that character. 

 For instance, Cephonodes picus has an armed foretibia, while hi/las possesses 

 no thorn, but hi/lns has a decidedly more specialised sexual armature. 



The spinosity of the tibiae is often an accessory character found in the 

 species which show reduction in the appendices of the head and thorax. But 

 the appearance of the spines is not invariably associated with a reduction of 

 the legs in length, nor are the spines always met with on reduced tibiae. 

 Spinosity of the tibiae occurs commonly among Acherontiinae and Ambulicinae ; 

 it is also found in some genera of Sphim/idae semanophorne. The spines appear 

 first near the apex of the tibia, and the foretibia is the first, the midtibia 

 the second, and the hindtibia the last to acquire spinosity. The hindtibia is 

 frequently much more densely spinose than the midtibia, and the foretibia 



