( 410 ) 



this it would ajipt'iir tliat tlie stuniite ui Jifr/Jufm/.s had preserved thu more ancestral 

 shape, and tiiat the asymmetrical one was the yonnger develoi)ment. We think just 

 the reverse is the case. For in J/, venata, as in Cephonodesjanus, we find the teutli 

 sternite divided into two processes, curving laterad at tip in venata, as in Sesiu, etc. 

 This rciiata sternite, representing the essential features of the divided sternite of 

 the allied genera from Sesia down to Madoryx and Pacln/lia, is a more ancestral 

 ty]ie than the apj)arently simple sternite of the other JIaemorrhagia. As venata 

 agrees structurally with /i/ri/ormis, etc., except in the tenth ahdominal segment and 

 the penis-sheath, there must he a connection between the divided and the simple 

 sternite. We have shown under Ceplio nodes that the apparently simple tenth 

 tergite of hylas, etc., is the result of the reduction of the left lobe, which remains 

 vestigial at the base of the long right lobe. On looking over the great numl>er of 

 dii-sections o^ llaemorrl/agia, we find that there is in many cases, at the base of the 

 ventral i)rocess on the right side, a piece of chitin separated from the jjrocess by the 

 vestige of a groove (PI. XLllI. f. 25, r) ; this piece is doubtless the rest of 

 the right process of the sternite. We regard, therefore, the single asymmetrical 

 ]ir(icess of thi/sbe, staudinyei'/, etc., homologous with the asymmetrical left ])rocess 

 of the divided sternite of »(?/i'a<n, and think that the nearly symmetrical process of 

 J'licifonnis is a derivation from an asymmetrical one. 



The difference between the right and left clasper is obvious in all species, but 

 more marked in some than in others (PL LI. i. 17 — 21 ; LII. f. 4. 5). The claspers 

 ar(! most similar in dijinis (PI. LI. f. 21). The left harpe {H,l) is always smaller 

 than the right one ; it has never a prominent process, while the right harpe is in 

 many species })roduced into a more or less clubbed process, generally armed at the 

 end with spines or clothed with long bristles. We repeat, it is the left harpe which 

 is the more reduced, while it is the right ])rocess of the tenth sternite and the left 

 process of the tenth tergite which is obliterated in most Haemorrhagia and some 

 Vepli07iodes. This is remarkable, for it is not difficult to perceive that it should 

 have been the left process of the tenth sternite which disappeared, instead of the 

 right one, if the obliteration of the left process of the tenth tergite and of the left 

 harpe of the ninth segment was due only to an inherent tendency in these segments 

 to become reduced on the left side. As in the case of the tenth segment it is the 

 left side of the dorsal plate and the right side of the ventral plate which atrophy, 

 it is clear that there must be some other reason for this peculiar development. 



Comparing the most primitive tenth segment, as jireserved in H. venata, with 

 the most sj)ecialised one, as found in Cepkonodes leucogaster, we see that at the 

 highest degree of sjiecialisation attained, the double force{)s, which moves vertically, 

 is replaced by a single forceps moving horizontally (PI. XLIII. f. 0. 10). At first 

 sight it apj)ears to be great waste to drop the right ventral process and to move the 

 left one towards the right side and upwards, instead of dropping the left one and 

 bringing the nearer right one in the position in which the sternal process is situated 

 in leucogaster. But the species oi Haemorrhagia and several Ceplionodes show that 

 the right ventral process is lost without the movement of the left one towards the 

 right side having begun. Therefore it is obvious that the absence of the process is 

 not dependent on the twisting of the segment to form a horizontal forceps, and that 

 the complete twisting of the segment, as observed in C. Icueogaster, took place 

 probably after the loss of the right ventral process. 



Besides the reduction of the bifurcate sternite to one with a single process, we 

 observe another line of development, illustrated by Cepkonodes jantis and hylas. 



