( 28 ) 



The table inserted above shows the gradual reduction of the organs mentioned 

 in the table. It will be observed that the highest forms, or the most reduced in 

 this case, become similar in structure in consequence of the loss or reduction of 

 organs, thougji tlie insects are of different origin. Such apparently convergent 

 devel()j)ment is remarkably well illustrated by this tribe of Hawk Moths. 



Tlie naked streak on the innerside of the second segment of the palpus reminds 

 one of the palpus of Theveira and allies, as do amongst the Acherontticae the 

 palpi of Megaronna and Achcrontia, though in other respects. 



The great number of genera in the Old World, and the occurrence in the c? 

 of a friction-patch and a completely divided tenth tergite only in some Old- World 

 forms, together witli the fact that the Aclierontiicae are represented in the New 

 World only by one species, and the third tribe Sphingulicae not at all, show clearly 

 that the subfamily Acherontihiae is of Old-World origin. The same applies to 

 the allied subfamily Ambiiliciiiae. 



Key to the genera : 



a. Third segment of palpus naked, pointed, 



prominent ...... b. 



Thipd segment of palj)us not naked . . c. 

 h. Long terminal spur of hindtiliia a little 

 longer than tibia ; clasper with 

 friction-patch (c?) . . . .V. Xunthopun. 



Long terminal spur of hindtibia shorter 

 than tibia ; clasper without friction- 

 patch XVIL Cocytius. 



c. Pnlvillus present r/. 



„ absent, or reduced to a short 



triangular lobe t. 



(I. Foretibia with spines . . . . . e. 



„ simple j. 



• e. Two pairs of spurs to hindtibia . . . /. 



One pair „ „ „ „ . . XXXVI. Thumnoeclia. 



f. Paronychium with two lobes on each 



side ; ground-colour of hindwing 



yellow VI. PitnogeiKf. 



Paronychium with one lobe on each 

 side; ground-colour of hindwing 

 not yellow y. 



g. Spurs densely spinose, long apical one 



of hindtibia half the length of the 

 first tarsal segment . . . XVI. Praedora. 

 Spurs not spinose, long apical one of 

 hindtibia more than half the length 

 of the first tarsal segment . . . Ii. 

 h. D'- of hindwing very oblique, twice the 



length of D^ ; Africa . . . XL Pemba. 

 W of hindwing not very oblique, as long 



as or shorter than D^ ; America . . /. 



