SPHINGIDES. 361 



processes. (2) Oblique stripes : As in Sesia (Hemaris). (3) Subspiracular stripe : 

 As in Sesia (Hemaris), Alacroglossa, &c. (4) White thoracic lines: As in 

 Sphinx ligustri. (5) The appearance and arrangement of the chief tubercles. (6) 

 Shape of head : As in young Sphinx and Stnerinthus and adults of many other 

 genera. (7) Sphinx-like attitude : Also the fact that it is chiefly marked in young 

 larvae. (8) Position on leaves and twigs of foodplant, at different times in larval life. 

 (9) Shagreen dots : With bristles, and the times at which they appear and persist 

 (Smerinthus, Sphinx). (10) Individual differences in shade of ground colour : As 

 in Smerinthus. (11) Distribution of shades of ground colour : As in Smerinthus, 

 Manduca (Acherontia), Sphinx. (12) Probable slight susceptibility of larval tints to 

 surrounding colours : As in Smei inthus, Sphinx. (13 ) The colours of the 

 spiracles in the last stage : As in Sphinx. (14) Change of colour before pupation : 

 As in Smerinthus. (15) The shape and texture of the pupa : As in Amorpha 

 populi. 



Poulton adds that nearly all these points of resemblance* are 

 very striking, and appear to prove that the larva has the closest 

 affinity to the Sphingids and especially to the genus Smerinthus. 

 He then details the peculiarities and apparent differences as follows : 



(1) Ova : Very different in colour. (2) Expansion of spines : Immediately 

 after hatching. (3) The presence of four thoracic spines and the anal spine. (4) 

 Absence (?) of subdorsal line. (5) The length of the first stage. (6) The ridges on 

 abdominal segments. (7) The terrifying mark: Position and concealment during 

 rest, but origin much as in Eumorpha {Choerocampa). (8) Loss of caudal horn 

 in last stage, but certain Sphingid larvae also lose the horn. (9) Only four 

 stages in the ontogeny. 



Discussing these differences and peculiarities, Poulton says 

 that 1, 2, 6 and 7 are entirely adaptations to the peculiar conditions 

 of the larva and cannot be considered to prove any great divergence 

 in affinity, any more than the various adaptations which form 

 such sharp characteristics within the group of the Sphingids them- 

 selves, such as the terrifying marks ot Eumorpha (Choerocampa), etc. 

 It is impossible at present to decide whether 5 and 9 are adaptive. 

 The subdorsal line (4) may be represented in part, and points 3 

 and 8, in reality indicate affinity as much as divergence ; thus, the 

 caudal horn degenerates in size and shape in the latter stages of many 

 Sphinx larvae. He says that it nearly disappears in the last stage of 

 Theretra (Choerocampa*) pore ellus ; it is absent from all except the earliest 

 stages (if indeed it is present in these latter) of Thaumas (Deilephila) 

 vespertilio and Pterogon oenotherae (Weismann, Studies in the Theory of 

 Descent, pp. 209 and 259). The ontogeny of Aglia is more exaggerated 

 than that of any Sphingid larva ; it commences with a more 

 specialised caudal horn than that which any Sphinx possesses, and 

 associated with a specialised remnant of the spinous covering of 

 allied Bombyx larvae ; and suddenly, at the last ecdysis, all these 

 prominent features are lost as completely as is the horn f in the 

 later stages of certain Sphingid larvae. 



There is no need to follow Poulton in detail through all the 

 interesting facts by means of which he attempts (loc. cit., pp. 568 

 et sea.) to show the affinities or " natural position" of the Sphingids. 

 He points out the well-known facts, without, however, showing the well- 

 known evolutionary principle involved, that within the Attacid stirps, 



* Similar habits necessitate similar needs, whilst a common ancestry often 

 leads to the needs being met in a somewhat similar manner (Tutt). 



t The horn is not lost so suddenly in any Sphingid larva as it is, for example, 

 in Aglia tau. In Theretra porcellus it is never really a horn as generally understood 

 mong the Sphingids. 



