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EV AGIN ABLE TUBERCLES OF CATERPILLARS 381 



on each side of and under the odoriferous puff-balls of the hinder edge of the 

 penultimate segment (Fig. 366, 13). The club or head is armed with hairs or 

 bristles, which, in Heliconius, are like the scales of a butterfly. 



In the caterpillars of certain blue butterflies (Lycaenidae) is an in- 

 ternal osmeterium, being a very minute sac which is everted from a 

 transverse slit on the top of the 7th abdominal segment. Its func- 

 tion is quite the opposite of those of the caterpillars of other fami- 

 lies, since the sac exudes a sweet fluid very attractive to ants, which 

 may be diffused more widely by the delicate spinulose bristles crown- 

 ing the summit. W. H. Edwards states that in several species of 

 Lycaena, besides that on the 7th abdominal segment, there is on 

 the 8th segment a pair of minute dorsal evaginable tubercles. 



A pair of small ramose odoriferous glands are said by Siebold, who 

 regarded them as alluring glands, to occur in Argynnis, Melitaea, and 

 Zygaena, to be situated near the orifice of the oviduct, and Scudder 

 has detected them near the anus of the female pupa of Danais arcliip- 

 pus. The appearance of the odoriferous glands in the pupa of Van- 

 essa io is well shown by Jackson (Fig. 366, u). They develop as two 

 tubular ingrowths of the hypodermis, perfectly distinct one from the 

 other, each having its own separate aperture to the exterior. In 

 Fig. 366, 14 the condition of parts is nearly as in the imago, the glands 

 being situated below the rectum and opening of the oviduct. In 

 both sexes of another Brazilian butterfly (Didonis biblis) on the me- 

 dian line of the abdomen between the 4th and 5th segments are two 

 roundish vesicles covered with short gray hairs, which emit a dis- 

 agreeable smell. 



It is possible that the dark-green fluid in Parnassius, secreted by an evaginable 

 gland, and which is moulded into shape by the scimetar-shaped peraplast (Scud- 

 der), is formed by the homologues of the anal glands of other butterflies. 



FIG. 366. Scent-glands of insects: 1. Anal eversible glands of Eleodes. After Gissler. 

 2. Anal eversible glands of Blaps. After Gilson. 3. Anal glands (agl) of Carab-w hortensis: 

 rs, reservoir ; d, excretory duct ; i, intestine ; r, rectum. After Kolbe. 4. Prothoracic spraying 

 apparatus of Cerura vinula : gl, the gland ; d, its duct, with tenidia ; t, the spraying tubes ; 

 in, muscles; rm, retractor muscles. After Klemensiewicz. 5. The thoracic glandular sac of 

 Macruroeampa marthexia : ffl, the glandular sac ; d, its duct ; e, peritracheal epithelium ; t, the 

 spiral threads or tsenidia. 6. Irregular separate masses of chitinous ridges on the cuticular lining of 

 the wall of the sacs of Maururocampa tnarthesia. 1. Osmeterium (os) of the larva of Papilio 

 machaon at rest: rm, the retractor muscles at the ends; m, the numerous oblique muscles; 

 dm, dorsal longitudinal muscles; t, trachea; oe, oesophagus ; gan g, brain ; l.head; 2, 3, 4, thoracic 

 segments. 8. Osmeterium (os) of one side, enlarged : ff, glandular portion at the base ; d, depres- 

 sions in the cuticula of the glandular portion; t, trachea. This and Fig. 7 after Klemensiewicz. 



9. Eversible dorsal glands (ev. gl) of larva of Orgyia- ItUOOsMgma in Stage II : yc, glandular 

 cells at bottom of the crater-like depression ; m, retractor muscle ; p, poison gland-cells of the root 

 of the seta (*) ; o, cuticula ; hyp, hypodermis ; A, portion of the cuticle and hypodermis enlarged. 



10. Lateral eversible gland of Ifypercliirta io, Stage II : rm, retractor muscle ; oen, cenocvtes. 



11. The same as Fig. 10, but representing a section through one side of the eversible gland. 



12. A, end of body of ColcenisjwHa ; ev, eversible anal gland ; oa, odoriferous appendages ; B, the 

 same in Heliconiutt apueudes, side view ; C, odoriferous appendages of Colmnis dido in fresh 

 condition ; />, tested with alcohol and benzine. 13. Odoriferous appendages oflfeliconius eucrate, 

 head cleansed. Figs. 12, 13, after F. Muller. 14. Odoriferous glands (offl) in the pupa of Vanessa 

 io : r, rectum ; h, the folds of hypodermis which forms the terminal papilla of the abdomen ; 

 ov, oviduct. After Jackson. 



