“These cases, with other refuse matters, collect in quantity within the bowel, which becomes distended, since it has no opening. The imprisoned larva, having little more than enough room for turning, must be freed of these objectionable residua.... In a word, the larva turns its head upon its stomach, and pushes the former towards the base of the cell until its position is reversed, the tail being outwards; and, thus placed, it laps up all residue of food, especially from its old clothes previously referred to, until they are dried, and practically occupy no space. It now throws up its stomach and bowel, with all their contents, and without detaching them from its outer skin, which is moulted as before, but in this instance to be pressed against the cell, so as to form for it an interior lining. The dejectamenta of the bowel in this way lie between the cast skin and cell-wall (as seen at e, Fig. 577), and so the larva remains absolutely unsoiled. It now turns its head and resumes its old position, joining its cocoon to the edges of its last cast skin, so that its habitation is relined, it is cleansed, and air can still pass to it through the imperceptible openings left by the bees in the sealing. This point is of radical importance, since breathing is carried on pretty rapidly during the latter part of its subsequent transformations, the absorbed oxygen permitting then of a production of heat, and causing also considerable diminution in weight.”
Fig. 577.—Larva and pupa of honey-bee in their cell: SL, spinning-larva; N, pupa; FL, young feeding larva; co, cocoon; sp, spiracles; t, tongue; m, mandible; an, antenna; w, wing; ce, compound eye; e, excrement; ex, exuvium.—After Cheshire.
As to the passage of air into the bee’s cocoon, Cheshire states that before the cocoon can be built, a cover, technically called sealing, is put over the larva by its nurses. These covers are made of pollen and wax, and are pervious to the air. They are more convex and regular in form than those sealing in the honey.[[102]]
THE PUPA STATE
The word pupa is from the Latin meaning baby. Linnæus gave it this name from its resemblance to a baby which has been swathed or bound up, as is still the custom in Southern Europe. The term pupa should be restricted to the resting inactive stage of the holometabolous insects.
Lamarck’s term chrysalis was applied to the complete or obtected pupa of Lepidoptera and of certain Diptera, and mumia, a mummy, to the pupæ of Coleoptera, Trichoptera, and most Hymenoptera. Latreille (1830) also restricted the term pupa to the “oviform nymph,” or puparium, of Diptera. Brauer applies the term nymph to the pupa of metabolous insects.
Fig. 578.—Pupa obtecta: a, of Sesia, with its cocoon-cutter on the head; b, of Tortrix vacciniivorana.
The typical pupa is that of a moth or butterfly, popularly called a chrysalis. A lepidopterous pupa in which the appendages are more or less folded close to the body and soldered to the integument, was called by Linnæus a pupa obtecta; and when the limbs are free, as in Neuroptera, Mecoptera, Trichoptera, and the lepidopterous genus Micropteryx it is called a pupa libera (Fig. 579). When the pupa is enclosed in the old larval skin, which forms a pupal covering (puparium), the pupa was said by Linnæus to be coarctate. The pupa of certain Diptera, as that of the orthoraphous families, is nearly as much obtected as that of the tineoid families of moths, especially as regards the appendages of the head; the legs being more as in pupæ liberæ (Fig. 580).