. The American entomologist. Entomology. THE AMERICAN ENTOMOLOGIST. f6s limb. They vary much in form, and may be more or less obsolete. Fourthly. Between them is what may be called the rectal piece {rp\ consisting of a piece more or less well marked and ele- vated, especially around the closed rectum. It is principally by the leverage obtained by the hooking of the sustainers in the re- taining membrane, which acts as a swing- ing fulcrum, that the chrysalis is prevented from falling, after the cremaster is with- drawn from the larval skin. It is also principally by this same means that it is
. The American entomologist. Entomology. THE AMERICAN ENTOMOLOGIST. f6s limb. They vary much in form, and may be more or less obsolete. Fourthly. Between them is what may be called the rectal piece {rp\ consisting of a piece more or less well marked and ele- vated, especially around the closed rectum. It is principally by the leverage obtained by the hooking of the sustainers in the re- taining membrane, which acts as a swing- ing fulcrum, that the chrysalis is prevented from falling, after the cremaster is with- drawn from the larval skin. It is also principally by this same means that it is enabled to reach the silk with the cremas- tral hook-pad. Yet the rectal ligament (Fig. 67.). 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 form
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Keywords: ., bookcentury1800, bookdecade1860, booksubjectentomology, bookyear1
