THE COCOON-BREAKER 



635 



Our attention 1 was drawn to this subject by a rustling, cutting, and tearing 

 noise issuing from a cocoon of Ac.tias luna. On examination a sharp black point 

 was seen moving to and fro, and then another, until both points had cut a rough 

 irregular slit, through which the shoulder of the moth could be seen vigorously 

 moving from side to side. The hole or slit was made in one or two minutes, and 

 the moth worked its way at once out of the slit. The cocoon was perfectly dry. 

 The cocoon-cutter occurs in all the American genera, in Samia ci/nthia, and is 

 large and well marked in the European Satnrnia pavonia-minor and Endromis 

 versicvlora. In Bombys mnri the spines are not well marked, and they are 

 quite different from those in the Attaci. There are three sharp points, being 

 acute angles of the pieces at the base of the wing, and it must be these spines 

 which at times perform the cutting through of the threads of the cocoon described 

 by Reaumur, and which he thought was done by the facets of the eyes. It is 



FIG. 591. Cocoon-cutter of the Luna 

 moth : front view of the moth with the shoul- 

 ders elevated and the rudimentary wings hang- 

 ing down: x, cocoon-cutter ; p, patagium. B, 

 represents another specimen witli fully devel- 

 oped wings : nix. scutum : xt, scutelluiu of the 

 mesothoracic sfirment ;. cocoon-cutter, which 

 is evidently a modification of one of the pieces 

 at the base of the fore winirs : it is surrounded 

 by membrane, alluwinsr free movement. < 'and 

 />. different views of the spine, magnified, 

 showing the five or six irregular teeth on the 

 cutting edge. 



FIG. 592. Larva and pupa of a wood-wasp 

 (Rhopalum\ enlarged : h, temporary locomotive 

 tubercles on head of pupa. Trouvelot del. 



well known that in order to guard against the moths cutting the threads, silk- 

 raisers expose the cocoon to heat sufficient to destroy the enclosed pupa. In 

 Platysamia the cocoon-cutters, though well developed, do not appear to be used 

 at all, and the pupa, like that of the silkworm and other moths protected by a 

 cocoon, moistens the silk threads by a fluid issuing from the mouth, which also 

 moistens the hairs of the head and thorax, together with the antenna?. It 

 remains to be seen whether these structures are only occasionally used, and 

 whether the emission of the fluid is not the usual and normal means of egress 

 of the moth from its cocoon. Dr. Chapman remarks that throughout the obtected 

 moths "there are many devices for breaking through the cocoon : specially con- 

 structed weak places in the cocoon, softening fluid, applied by the moth, assisted 

 by special appliances of diverse sorts, such as in Hybocampa 2 and Attacus," etc. 

 As to the fluid mentioned above, Trouvelot states that it is secreted during 

 the last few days of the pupa state, and is a dissolvent for the gum so firmly 



1 Amer. Naturalist, xii, pp. 379-383. 



2 Hybocampa milhauseni, Dr. Chapman tells me, has a pupal spine (imperfectly 

 present in Cerura) with which it cuts out a lid of the cocoon. 



