40 BRITISH LEPIDOPTERA. 



into nutrient fluids and lowly differentiated units, from which the 

 imago is subsequently built up by histogenesis, a process akin to 

 embryological devolopment, has an important bearing on the subject. 

 He writes : " If we examine a section of a pupal antenna or leg (in 

 Lepidoptera) we shall find that there is no trace of the corresponding 

 imaginal organ, until shortly before the emergence of the imago." It 

 is quite possible that there may never be a corresponding imaginal 

 organ developed within it, but that it is a purely pupal organ, a 

 remnant of a structure once functionally active but now no longer so, 

 e.g., the pupal maxillary palpi of the Sesiids. Poulton then says : " In 

 the numerous species with a long pupal period the formation of 

 imaginal appendages within those of the pupa is deferred until very 

 late and then takes place rapidly in the lapse of a few weeks. This 

 also strengthens the conclusion that such pupal appendages are not 

 mere cases for the parts of the imago, inasmuch as these latter are 

 only contained within them for a very small proportion of the whole 

 pupal period." To both parts of this statement we take objection, for 

 whilst it may be quite true for many pupa?, it is utterly contrary 

 to fact for others. The Tamiocampid pupa?, being formed in July- 

 August, perfect their imagines in September, and the living perfectly- 

 developed imago exists inside the pupa until March or April of the 

 following year. Norman notes that the white stigma on the imaginal 

 forewings of Panolis piniperda is distinctly visible through the pupal 

 skin in early October, although the imago will not emerge until the 

 following March-April. So, also, Dadd says that the white stigma of 

 the imaginal f orewing of Valeria oleagina can be seen through the pupal 

 wing some six months before the emergence of the imago. The latter 

 part, too, is only true to the extent that the imaginal organs, as such, 

 usually exist in the corresponding pupal organs only for a short time 

 before emergence, but certainly the wings are all the time wings and 

 not merely the places where wings are to appear. 



We have already (vol. i., p. 22) referred to the fact that Tichomi- 

 roff and Graber found eleven abdominal segments in the embryos of 

 Bombyx mori and Gastropaclia quercifolia respectively. Normally, 

 however, the lepidopterous larva has but ten abdominal somites, and 

 in some Geometrid larva? only nine can be detected. The pupa? of 

 many species show distinctly that the abdomen consists of ten 

 segments, and that the confused mass beyond the 8th abdominal 

 segment of the larva really consists of two segments, much more 

 definite, however, in the larva? of some families than others. In the 

 pupa, the 9th abdominal segment is generally smaller than, but quite 

 as distinct as, the preceding segments, whilst the 10th segment bears 

 the cremaster (if one be present), analogous with the anal flap of the 

 larva. There is something to be said for Poulton's view that the 10th 

 abdominal segment of the pupa may be really composed of two 

 segments, an upper cremastral-bearing part, and the lower part, but 

 it seems to us that the former is analogous with the anal flap, the 

 latter with the anal prolegs of the larva. We agree with him that the 

 line of separation between the upper and lower parts of the 10th 

 abdominal segment, as exhibited in his Morphology of the Lepidopterous 

 Pupa, fig. 7, p. 196, " corresponds to the posterior part of the chink 

 beneath the larval anal flap." He adds that " the constriction which, 

 in certain pupa?, encircles the base of the terminal spine, would then 



