. The American entomologist. Entomology. Ideal representation of the anal subjoint of the larva of Vianessa antiopa, from behind, with the spines removed and all the parts forced apart by pressure so as to show the homol- ogies of the parts in the chrysalis which are concerned in pu- pation ; the homologies indicated by corresponding letters in Fig. 68, except that r (the rectum) corresponds with / r in Fig. 68 (after Riley). plays a most important part, and in some species a more important part even, in my estimation, than the membrane itself. The tracheal ligaments, which, from a study of sp
. The American entomologist. Entomology. Ideal representation of the anal subjoint of the larva of Vianessa antiopa, from behind, with the spines removed and all the parts forced apart by pressure so as to show the homol- ogies of the parts in the chrysalis which are concerned in pu- pation ; the homologies indicated by corresponding letters in Fig. 68, except that r (the rectum) corresponds with / r in Fig. 68 (after Riley). plays a most important part, and in some species a more important part even, in my estimation, than the membrane itself. The tracheal ligaments, which, from a study of specimens plunged in alcohol when the larval skin was about half shed, I was at first inclined to believe important auxili- aries, are, I am now satisfied, of very little or no service in most cases. The rectal ligament is a constant physiological factor, and its importance cannot be ascertained by attempts to sever the membrane at the critical moment, because in such attempts the ligament is more or less drawn out be- yond the power of the sphincter muscles in the chrysalis to control it. Dissected immediately after suspension, and the subjoint of the larva will be found to be bathed, especially between the legs and around the rectum, in an abundance of translucent, membranous material. An hour or more after suspension the end of the forming chrysalis begins to separate from the larval skin, except at the tip of the cremaster (see Fig. 70, b). Gradually the skin of the legs and of the whole sub- joint stretches, and with the stretching, the cremaster elongates, the rectal piece re- cedes more and more from the larval rec- tum, and the sustentor ridges diverge more and more from the cremaster, carrying with them, on the sustainers, a part of the soft membrane. If a larva be carefully (Fig. 68.). Anal parts of chrysalis of Vanessa antiopa^ just prior to final extraction from larva skin : c, cremaster ; chp, cremas- tral hook-pad ; h, one of the hooks more enlarged ; vir^ ven- tral
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectentomology, bookyear1
