EVERSIBLE GLANDS OF CATERPILLARS 



379 



mal cells, as seen at C. In some of the nuclei, indistinct nucleoli are seen, and 

 deeply stained granules, especially around the periphery of the nuclei. At B is 

 represented a section on one side of the middle, but still showing the spacious 

 lumen. In the section represented by (7, the knife passed through the process 

 still nearer the outer edge, and near the base; at (7 1 , three of the glandular 

 cells, with their large, deeply stained nuclei, are drawn. A transverse section 

 at D shows the large lumen or cavity (I). 



As to the function and homologies of these structures, it is difficult to decide. 

 We have never noticed that they give off any odor, though they may prove to 

 be repugnatorial ; they are not visible in the fully grown, living insect, being 

 concealed by the long, dense hairs clothing the body ; they are not spraying 

 organs, as they are imperforate at the end, not ending as the lateral, eversible 

 glands of Hi/perchiria io, etc., in a crateriform orifice. 



They may be permanently everted glands, or osmeteria, which have, by dis- 

 use, lost their power of retraction and their crateriform opening, as well as the 

 power of secreting a malodorous fluid. 



FIG. 365. Section of lateral processes of larva of Megalopyge. 



In certain of the butterflies, the Heliconidae (Colsenis, Heliconius, 

 Euides, and Dione), there is thrust from the end of the abdomen a 

 pair of large, irregular, rounded, eversible glands, which give out 

 a disagreeable odor, and are consequently repellent, and which seem 

 to be the homologues of the odoriferous glands of other butterflies. 



The large, soft, rounded, eversible glands, looking like puff-balls or a rounded 

 pudding (Fig. 366, 12), are everted, when the butterflies are roughly seized, from 

 the dorsal side of the penultimate segment of the abdomen. The males possess 

 two smaller tubercles on the inside of the anal claspers or lobes. Miiller also 

 detected, in the females of various species of the Heliconidse enumerated above, 

 a pair of club-shaped processes like the balancers of flies, which are thrust out 



