38 BRITISH LEPIDOPTERA. 



expanding and attaining their full size, the specimen being a specially 

 large and well developed female. Similar observations on other species 

 have been frequently recorded. Chapman notes (Ent. Mo. Mag., xxx., 

 p. 54) that on January 19th, 1894, at 2 a.m., a Doritis apollina had 

 emerged on a mantel- shelf in a room with a fire, and at a temperature 

 of 73°F. or 74°F. It searched in vain for some time for a suitable 

 spot on which to rest for wing expansion, so at last he confined it in 

 a muslin bag and took it into another room with a temperature of 

 51°F. At 9 a.m. it was resting quietly, but with wings absolutely 

 unexpanded. It was then taken back to the warm room, and, in five 

 minutes, the wings were found well advanced in development, and it 

 shortly became a perfectly developed specimen. This is the only case in 

 which lowered temperature is suggested to have been the active factor 

 in the retardation of wing-expansion. Many cases of retarded wing- 

 expansion have been recorded, possibly some may be due to this cause ; 

 Chapman states that he has known an imago extracted too early from 

 the pupa to expand its wings two days after. We remember a similar 

 case with Aglais urticae. 



There are numberless subjects bearing more or less indirectly on 

 the metamorphosis in Lepidoptera that might be discussed, but these 

 must stand over until a later volume. 



CHAPTER III. 



THE EXTERNAL MORPHOLOGY OF THE LEPIDOPTEROUS PUPA. 



The pupal stage is nominally the quiescent state preceding the 

 imaginal stage of insects with complete metamorphosis ; really it is, in 

 such, that stage in which the vital processes are most active and most 

 readily impressed by external conditions. It is analogous with, but 

 very different from, the nymph stage of those insects with incomplete 

 metamorphosis, and differs considerably even in those insects that have 

 a pupal stage. In the Trichoptera, the pupa resembles the perfect 

 insect in general form, is at first quiescent, but apparently becomes 

 active before the imaginal ecdysis occurs, although it is the now all but 

 perfect imago within the pupal shell that is really so ; in the Ephe- 

 merids, the penultimate ecdysis is accompanied by a change of form 

 to the winged condition, the imaginal ecdysis being simply a casting 

 of the skin after the winged state has been assumed, whilst the 

 Odonata also have no pupal stage, these insects, in the stages preceding 

 the imaginal, being known as nymphs. The lepidopterous pupa shows 

 great variation in its structure and capacity for movement, the form 

 with limbs and appendages free from the abdomen and the abdominal 

 segments freely movable on each other, being known as a pupa-libera, 

 that with the appendages, &c, partially free being known as a pupa- 

 incompleta, whilst the pupa in which the appendages are soldered to 

 the abdominal segments and in which movement of the latter is 

 restricted to the incisions between 4-5, 5-6 and 6-7 is known as a 

 pupa-obtecta. The most specialised forms of pupa? such as those of 

 Leucophasia sinapis, Cupido minima, &c, have no movable abdominal 



