BY VERA IKWIN SlIITH. 



521 



xxvii., tig 8 J its basal portion is united with the labnim-epipliaryux, to form the 

 basi-proboscis, and tlie ireu distal end is scarcely distinguishable. 



The tip of the labrum-epipharynx, in the pupa, does not reach beyond the 

 proximal half of the slieath enclosing it (Text-tig. 23), and the existence of the 

 enlarged, bilobed, distal portion is puzzling. No structure is contained within 

 it at any stage of development. The double nature of the sheath enclosing the 

 maxillary palp is also peculiar, but seems to suggest the presence, originally, of 

 well-developed maxillae, with their galeae and laeiniae. 



Between the lateral sheaths, just below tiie upper median one, there are, in 

 the very early pupa! stage tigured in PI. xxvii., tigs. 3 and 4, two small, tliin, 

 needle-like, chitin pieces, whicii are not enclosed in sheaths. These structures, 

 which do not appear in later stages, would seem, from their position, to repre- 

 sent rudimentary mandibles, though no trace of mandibles exists in the imago. 



Other swellings of the pupal skin, for which no apparent reason exists, 

 occur on the head. A small double vesicle is situated l)etween the base of the 

 antennae, and the sheaths for the mouth parts (PI. xxvii., fig. 7). .Just below 

 the eye on each side, in the position of the gena, is, a prominent, downwardly- 

 projecting, hollow vesicle. 



Stigmata. — A pair of lateral spiracles is present on each abdominal seg- 

 ment from the tirst to the seventh. The iirst six pairs are very prominent from 

 the earliest stages of pupal development, and are of compli(;ated structure. 

 The greater ijortion of eacli one lies outside the body wall, in the region lietween 

 it and the pupal skin, which is here raised into a sharp peak, and strengthened 

 by a funnel-shaped piece of chitin. The wide mouth of the funnel faces in- 

 wards, and serves to protect the underlying stigmatie apparatus. This consists 

 of a pear-shaped bulb with thick muscular walls, penetrated by a fine lumen, 

 and terminating in a long slender tube, with strongly chitinised walls, wiiich 

 runs through the neck of the funnel, and extends out to the larval skin ( Text- 

 fig. 19) . The tip of the spiracle appears on tiie outer surface of the larval skin 

 as a dark brow-n projection in the region of the larval stigma. A slender tra- 

 cheal tube, g-iven off from the base of the bulb, and opening independently on 

 the pupal skin, is probably the original larval tracheal tulte, the pupal sjiiracle 

 being a secondary growth. These structures will be considered more fully in a 

 later paper, dealing with the tracheal system of larva and pupa. A trachea of 

 the ordinary type connects the base of the stigmatie bulb with a circular aperture 

 in the body wall. Shortly before the emergence of the imago, this tube becomes 

 detached from the body, and the whole stigmatie apparatus is left behind in the 

 pupal skin (PI. xxvii., fig. 9). The only trace of it which remains on the body, 

 is a wide, deep hole, with chitin rim, on the lateral margin of each segment 

 (Text-fig. 20). 



The spiracles of the seventh )iupal segment differ from the rest. They pro- 

 ject very little beyond the body, and are of simple structure, lacking the gi'eat 

 development of chitin supports . The reason for this is seen when the larval skin 

 is dissected away from the dorsal wall of the pupa (PI. xxvii., fig. 5) . The first 

 six alidominal segments correspond exactly with the segments of the larva, and 

 are in close contact with the larval walls in tlie region of the spiracles. But 

 the terminal segments undergo a considerable change in size and shape during 

 metamorphosis, becoming telescoped to a certain extent, and reduced in width; 

 so that a wide space is left round the posterior end of the pupa, and the seventh 

 pair of spiracles is not opposite the corresponding pair in the larval skin, and 

 cannot reach the exterior to function in lireathing. 



