THERETRA PORCELLUS. 103 



" dorsal spots " mentioned in the case of E. elpenor then appear 

 very distinctly on segments 5-1 1. The larvae continue to feed 

 for 11 days after the 3rd moult, at the end ot which period the 

 4th moult takes place, and the fifth instar is assumed, but without 

 the occurrence of any change of marking. The larvae then buried them- 

 selves, the complete development having taken 28-29 days (Weismann). 



Comparison of larvae of Theretra porcellus and Eumorpha 

 elpenor. — In T. porcellus the larva emerges from the egg with 

 the subdorsal line, the first stage of E. elpenor being omitted. This 

 suggests that the former is the younger species, i.e., has advanced 

 further in development. The subsequent course of development 

 of T. porcellus is essentially a repetition of the phenomena displayed 

 by E. elpenor and differing only in one point, viz., that all new 

 characters make their appearance one stage earlier than in the 

 latter species. This is the case with the transformation of the 

 green into a brown ground-colour, with the repetition of the 

 eye-spots on the remaining segments in the form of suffused black 

 spots ; and with the appearance of the light dorsal spots. Only 

 the eye-spots themselves appear, and the snout-like tapering of 

 the front segments occurs in the same stage as in E. elpenor, i.e., 

 the second (Weismann). [Compare anted, pp. 76-77. See also foot- 

 note p. 102.] 



Cocoon. — The cocoon is spun (in confinement) on the surface 

 of the earth under dead and dried bedstraw, is large and irregular 

 in shape, formed of loose and scanty, rather coarse, brown silk, 

 perhaps best described as forming an open network, rather than 

 a cocoon (Bacot) ; the larvae make a very open network cocoon 

 on the surface of the earth, working in bits of moss, &c. (Hellins) ; 

 spins up on the soil under moss or grass a slight cocoon of 

 silk and moss (Lambillion). Adkin gives (Proc. Sth. Lond. Ent. 

 Soc, 1889, p. 153) an interesting note as to a pupal chamber 

 formed by a larva in one of the folds of the leno in which it spun 

 up. The space was lined with a substance resembling a film of 

 gelatine, slightly flexible to the touch and apparently of a damp- 

 resisting nature ; he assumed it to represent the lining of the 

 earthen cell, made by larvae, when pupating under natural 

 conditions, but of so delicate a structure as to prevent its 

 being detected when a pupa is removed from the earth. After 

 the emergence of the imago it was found that the gelatinous lining 

 had almost disappeared. 



Pupa. — This pupa is at first sight indistinguishable from that of 

 E. elpenor except by size, being 3omm.-38mm. long instead of 35mm. to 

 45mm., and, on closer examination, the differences are seen to be such 

 that it is obvious that a description of the one without seeing the other 

 might easily apply to both, even if made with some care. It will, there- 

 fore, be more satisfactory to describe the pupa of T. porcellus by special 

 reference to the points in which it differs from that of E. elpenor. As to 

 the form of the pupa, it is at least as little flattened as that of E. elpenor. 

 The head is proportionally a little larger, the labrum is thrown a little 

 further back, and the maxillae in front of it (i.e., ventral to it) 

 project distinctly beyond it, and form the anterior point of the 

 pupa, the eye being directed exactly forward. The proboscis keel 

 is a little sharper and more prominent. The eye-spine terminates, 



