368 BRITISH LEPIDOPTERA. 



(elpenor, porcellus, gal Hi J, whilst they (i and ii) arise from a 

 single plate or raised area in the Sphingids (ligustri), Sesiids 

 (stellatarum), and Amorphids (ocellata)*. The caudal horn, however, 

 remains conspicuous, although its bifid tip and tubercles are usually 

 atrophied. Peck notes {Can. ■ Ent., viii., p. 239) that Smerinthus 

 astylus has its caudal horn armed with two spines appearing bifurcate 

 at first glance, the spines being present from its hatching. The 

 Sphingid caudal horn is characteristic of the superfamily. (although 

 many Attacid and other larvae have a very similar one), and when 

 absent, as in adult larvae of Eumorpha, Theretra, etc., it is re- 

 placed by a small, low, flattened elevation, and the segment is often 

 swollen (anted, vol. i., p. 50). The Sphingid larvae that feed on 

 low-growing plants are variable in colour, often dark, and are fre- 

 quently ornamented with striking spots which are supposed to have a 

 defensive purpose, and have been described as terrifying marks {loc. 

 cit., pp. 91 — 92). Those that live on trees and shrubs are usually 

 green in tint (uerii may be excepted), and their colour has been the 

 subject of considerable investigation (anted, vol. i., pp. 43 — 44 and 

 pp. 85 — 86). The remarkable attitude of Sphinx ligustri, from which 

 the name of the superfamily was derived, has no doubt a protective 

 value, and its probable mode of origin has already been discussed 

 (loc. cit., pp. 51 — 52), But apart from the position taken up by the 

 larva, the whole ensemble of the Sphingid larval position is sometimes 

 strikingly protective, e.g., Smerinthus ocellata, Elpenor (Deilephila) 

 hippophaes (loc. cit., p. 80), etc. 



Sharp writes (Insects, ii., p. 381) : " The larvae are remarkable for 

 their colours and form. The anterior segments are attenuated but 

 are capable of great retraction, so that, in repose, this shape is 

 concealed by the curious attitudes that are assumed. There is, 

 in nearly all cases, a conspicuous horn on the nth segment, and 

 the body at the extremity, behind the horn, is so much modified 

 that the two terminal segments look like little more than a pair of large 

 claspers. In the Choerocampini (Eumorphids), the thoracic segments 

 are retractile, and can be withdrawn into the more or less inflated 4th 

 segment and give the creature somewhat the appearance of a 

 miniature hooded snake. The larvae of Sphingidae do not bear 

 any conspicuous hairs — except during the first instar." Weismann 

 has discussed (Studies in the Theory of Descent), at length, various 

 views on the origin of the lines, bands and spots found on the 

 Sphingid larvae, and his conclusions have been generally accepted. 

 He suggests that the primitive markings of larvae were lines and 

 longitudinal bands, the spots appearing from interruptions of the 

 lines or bands, and he concludes from his studies of the Sphingids 

 that the subdorsal lines originated before the spiracular, although 

 it is possible that the dorsal is older than either (anted, vol. i., p. 

 44). As a matter of fact, generalisations of this kind must always 

 be accepted with caution ; no doubt ocellated spots and other 

 markings have originated in a variety of ways under stress of very 

 different and varied conditions. Piepers considers (Tijdschr. v. Ent., 



*The dorsals, i and ii, on the metathorax and mesothorax of Sphinx (ligustrij, 

 Sesia (stellatarum), and Amorpha [populi), are close together ; in SpJiinx on a 

 single plate, in Sesia (Macroglossum) on a little elevation, in Amorpha close 

 together but obscured by secondary hairs, apparently, however, on a raised skin 

 area, if not on a plate as in Sphinx (Bacot). 



