10 THE CATERPILLARS OF NEW ENGLAND. 



as explained to me explicitly by Mr. de Niceville, they form immense non- 

 retractile pillars, doubling the height of the body at this point ; or rather 

 the body is thus elevated and from the summit of the pillars "issue when 

 alarmed two long filaments or tentacles fringed A\it]i yery long hairs . . . 

 wliich it whirls around Ayith altogether astonishing rapidity, doubtless to 

 frighten away icheumnon flies." The caterpillar ]Mr. de Xiceville tells me is 

 not attended by ants, and therefore probably lacks the slit in the preceding 

 sco-ment.* In our species the caruncles are so minute as scarcely to be 

 yisible without a lens, but as pointed out by Dimmock their accompaniment 

 by hairs exposes still more surface to the air, and this giyes a better chance 

 for spreading any odors which they may secrete. lioth this organ and the 

 osmateria are so constructed as to present, says Dimmock, "the greatest 

 economy in the use of an odorous fluid ... by exposing suddenly a large 

 surface moistened wdth the fluid to the surrounding air." 



It is in e\-ery degree probable that other abdominal glands will be found 

 in caterpillars just from the egg, for the flaring-tipped hairs serially 

 arranged witli which so many juyenile and some adult caterpillars are 

 clothed {e. g. Pieris) may frequently be seen under the microscope to 

 exude at the tip a droplet of fluid, the source of which can only be pre- 

 sumed, as in similar appendages in lower Lepidoi)tera, to lie in a gland at 

 the base of the hair, which is always mounted upon a conical papilla. 

 But this is a subject upon which no writer has yet yentured either experi- 

 mentation or discussion. Other structures in the caterpillars of various 

 Lycaeninae at birth may possibly haye some similar purpose. 



Internal organization (Plate 62). 



In considering the external crust of the caterpillar and its appendages, 

 we have been able by its very organization to examine each part separately 

 without confusion ; for, by the division of the body into distinct regions, 

 and of the regions into separate rings, each bearing its special appendages, 

 the mind can readily locate these and recall them when necessary. The same 

 ^^'ill also be found to be true of the future stages of the animal's existence. 

 AMien, however, we come to the internal parts, the case is generally 

 different ; for both now and later the organs run in a longitudinal course 

 through the body and disregard in great measure not only the jointed struc- 

 ture but even the regional distinctions of the body. To systematize our 

 examination, therefore, we nuist treat them differently, and, separating them 

 into natural subdivisions according to their functions, discuss them in that 

 secpience which promises to give us the clearest conception of their use. 



As the 1)asis of the whole, we have the structural framework of the 

 animal, its outer crust ; and since })o\ver of movement is the primal need 



*Tbe tir.st segment on the right in Ilors- heing- retracted beneath it, and so altogether 

 field's figure is the first thoracic, the head out of sight. 



