﻿Sept 1895.] Packard. Scent Glands of Insects. Ill 



coarser than the particle of niercaptan which can be detected by the 

 nose. 



In those Arachnida which are provided with poison glands, these 

 scent glands are absent, but in certain Acarina and Linguatulida^, which 

 have no poison glands, there are various oil glands, stigmatic glands, 

 as well as scent glands, and in seizing a Thelyphonus with the forceps I 

 have observed it to send out from each side of the body a jet of offensive 

 spray. 



We find not infrequently in Mjriopods (Polydesmidte, Julidie, and 

 Glomeris) repugnatorial or the so-called cyanogenic glands, which are 

 either paired, opening on the sides of the body, or form a single row 

 along the median line of the under side of the body, Leidy describes 

 and figures the spherical glands of Jiiliis marginatus, of which there 

 are fifty pairs. These glands have been regarded as modified nephridia, 

 but are more probably coxal glands, and the homologues of the para- 

 podial glands of annelid worms. 



True coxal glands occur in Scolopendrella immaciilata on the 3d to 

 nth and the last segment, on the inner side of the base of the legs. 

 Homologous glands also occur in the same position in Campodea sta- 

 phylinus (also in C. cookei 2Xidi C. mexicana) on the ist to 8th abdomi- 

 nal segments, and Oudemans has described a pair of eversible sacs on 

 each side of segments i to 7 of Machilis. These eversible sacs in the 

 Synapterous insects are evidently modified coxal glands, and are prob- 

 ably repugnatorial as well as respiratory in function. 



The apparatus consists of an eversible gland, composed of hypo- 

 dermic cells, usually retracted by a slender muscle and with an efferent 

 passage, but the glands vary greatly in shape and structure in different 

 insects. In some cases these foitid glands appear not to be the homo- 

 logues of the coxal glands, but simply dermal glands. 



These repugnatorial glands are of not infrequent occurrence in the 

 lower or more generalized winged insects, and in situation and ap- 

 pearance are evidently the homologues of the coxal glands of the 

 Symphyla and Synaptera. 



In the ear-wigs (^Forficula and Chelidura) Meinert has detected a 

 pair of what he calls fcetid glands at the posterior margin of the dorsal 

 plates of the second and third abdominal segments. 



Vosseler also describes the same glands as consisting of a 

 retort-shaped sac, in whose walls are numerous small epidermal cells 

 and large single glandular cells provided with an efferent passage, 

 the fluid being forced out by the pressure of the dermal muscles, one 



