IMAGO OF PRIVET HAWK MOTH. 159 



The structure of the body as above described is probably typical of the 

 Lepidoptera, but the subject is one that calls for investigation. The region of 

 the first abdominal somites seems the most variable. 



The spiracles are vertical slits as in the previous stages. The last abdominal 

 spiracle, the eighth, is aborted. A slight scar indicating its position may some- 

 times be found in the male. The remaining spiracles are the prothoracic and 

 seven abdominal. The former is situated in the soft skin between the pro- and 

 meso-thorax, nearer to the prothorax. The first abdominal is the largest of the 

 whole series. It lies in the pleural membrane under the edge of the lateral piece 

 of the first tergum, i. e. on the abdominal side of the thoraco-abdominal constric- 

 tion 1 . The other spiracles are all situated in the pleural membranes of their 

 respective somites. If the interior of the pupa skin is examined, the cuticle 

 shed from the first portions of the tracheae may be found attached to all the pupal 

 spiracles, with the exception of the eighth abdominal, thereby shown to be closed. 



As to the mouth parts there is a labrum forming a narrow band with a 

 median process and a lobe covered with hairs at each outer angle 2 . Mandibles 

 are absent as articulated pieces, a characteristic feature, according to Walter, of 

 all the Lepidoptera save Micro-lepidoptera (Tineinae^ &c.). But from investigations 

 made upon caterpillars about to assume the pupal condition, it seems to me that two 

 stout pointed projections of the genae, lying to the outer side of the lateral lobes of the 

 labrum, are non-articulated representatives of these appendages. At any rate, they are 

 formed at the base of the caterpillar's mandible. The maxillae consist of a cardo and 

 stipes, imperfectly separated and immoveably united to the head. The palps are one- 

 jointed and bear a tuft of hairs. But the bulk of the maxillae, the antliae, consists of 

 the greatly-developed galeae. Each galea is prolonged into a long band spirally coiled 

 when at rest ; convex on its outer, concave on its inner, face, thus forming a 

 channel. The faces are strengthened by independent systems of chitinous spots 01 

 rings. The inferior edge of each channel bears a series of processes by which one 

 galea is strongly tied to the other; while its superior edge carries one or more 

 series of flat processes which overlap the corresponding processes of the other side. 

 The outer surface carries hairs and ' borers ' (ppotrypes\ the latter restricted to the 

 tip. The borers are simple in Sphinx. When well developed they appear to act 

 by piercing the nectaries of flowers or even pulpy fruits (e. g. as by Ophideres\ and 

 it is possible that they may also be to a certain extent organs of touch. The 

 labium is reduced to a membrane between the bases of the maxillae. Its palps are 

 three-jointed. The terminal joint, though small, is moveable. The second is deep, 

 compressed and grooved where it fits round the maxilla of its side, and the first 

 joint narrows to its base which is attached to a small cone 3 . 



1 Newport (article Insecta) calls the first of these two spiracles, mesothoracic (p. 923), the 

 second, metathoracic (p. 924) ; and Millie r-Blumenau uses the same expressions, connecting the 

 spiracles of the imago with the two closed thoracic spiracles he discovered in an aquatic cater- 

 pillar. See ante, p. 150, and p. 199 of paper quoted. In all the specimens I have examined they are 

 situated as above described. 



2 The prominence figured by Newport (article quoted) Fig. 377, as labrum, is a process of the 

 clypeus from which a muscle takes origin. The parts designated mandibles by him (as they are also 

 by Savigny) are really the lateral lobes of the labrum according to Walter. The only pupa of S. 

 Ligustri at my command in a fit state to decide the question appears to corroborate Walter's view. 



3 Walter has shown that in certain species of Micropteryx (Tineinae) there is a hinged and 

 toothed mandible ; a maxilla with moveable cardo and stipes, six-jointed palp, a thin lacinia and 



