<§> 347. THE INSECTA. 443 



alone, their number is smaller,'^^' and with those of the Lepidoptera, the 

 extremities of the six tubes of this kind are insinuated between the tunics of 

 the colon; while, with the imagines they are free/-""' AVith the Bupres- 

 tidae, the larvae have six, but the imagines only four, of these vessels.'-^* 



//. Organs of Peculiar Secretions. 



§ 347. 



A great number of the Insecta, in both their larval and their perfect state, 

 have glandular organs which secrete very varied products remarkable for 

 their specific properties. 



Many species have a secretory apparatus analogous to the cutaneous 

 glands of the Vertebrata, which have received the name of Glandulae odor- 

 iferae. These consist of round follicles situated under the skin, whose 

 very short excretory ducts open between the segments of the body, or be- 

 tween the articulations of its extremities. Their product emits a powerful 

 odor, and, with some species, is evacuated in the form of droplets,'^' or, 

 with others, covers the whole surface of the body, being perceived only by 

 its odor. <^' The disagreeable odor emitted by the Bugs is due to a fluid 

 secreted by a single, yellow, or red pyriform gland, situated in the centre 

 of the metathorax, and opening between the posterior legs/^' With other 

 Insecta, there are analogous secretory organs, concealed in the posterior 

 extremity of the abdomen, which copiously emit a fetid, troubled liquid, 

 through an orifice situated by the side of the anus. These Anal Grlands are 

 usually double, and consist of simple follicles whose secretory product 

 accumulates in round, or oblong contractile reservoirs.'*' With many 



(larva of variouä Lamellicornes); and Burmeister, of many Tenthredinidae, emit droplets of fluid from 



Trans, of the Eutom. Soc, I. PI. XXIV. fig. 10 (larva the surface of their skin from the least touch. Very 



of a Calosoma), and his Abhandl. z. Naturges- often the odor of this fluid reminds one of fresh 



chichte d. Calandra, loc. cit. fig. 3. poppy-juice. The fluid emitted from the cephalo- 



19 The larvae of the Apidae and Vespidae have prothoracic articulation, with Colymbetes and 

 only four uriniferous vessels ; see Sivammerdamm, Dytiscus, has a very nauseating order. I am un- 

 Bib. der Nat. Taf. XXIV. fig. 6 (larva of a bee) ; able to decide whether or not the transparent liquid 

 Suckow, in Heui<inger''s Zeitsch. III. Taf. VI. fig. which escapes with various Aphididae through two 

 180, and Ramdohr, loc. cit. Taf. XII. (larva of a tubes on their abdomen, belongs to this same cate- 

 Vespa) ; finally, Rathki, in Miiller^s Arch. 1844, gory of secretions. 



p. 36, Taf. II. (larva of a Gryllotalpa). 2 Certain Phryganidae, Hemerobidae, Crabron- 



20 See Lyonet, Traite, &c., PI. XIII., and idae, Scoliadae, Ichnemnonidae, &c., emit specific 

 Suckow, Anat. u. physiol. Untersuch. Taf II. odors without the secretion of their Glandulae 



21 See L. Dufour, Aim. d. Sc. Nat. XIV. 1840, odoriferae being visible. 



p. 114. Loew (^Entom. Zeit. 1841, p. 37, fig. 3) did 3 See L. Dufour, Recherch. loc. cit. p. 266, PI. 



not, probably, observe these canals in the larva of XVII. fig. 194. Moreover, the opinion that all the 



Buprestis mariana ; for, otherwise, he would not Bugs emit a bad odor is incorrect ; for with many, 



have regarded as ^uch the two caecal appendages as for example Syromastes, the Glandulae odori- 



at the upper extremity of the stomach, and which ferae e.xhales a very agreeable odor resembling that 



the Buprestidae have also in their imago-state (see of a fine bergamot pear.* 



^ 338). 4 These anal glands, which Burmeister (Handb. 



1 With Euprepia, and Zygaena, a fluid of this I. p. 157), Grant (Outlines, &c., loc. cit. p. 584) 



kind, yellowishly transparent, exudes under the and other anatomists have mistaken tor urinary 



collar ; and with many Melo'idae, Chrysomelidae, organs, consist, with the Dytiscidae and Gyrinidae, 



and Coccinellidae, it escapes from the knee-joints. of two simple, long and flexuous caeca, whose re- 



The larvis of these last Coleoptera, as well as thcsa servoirs, having two short excretory ducts situatai 



* { 5 347, note 3.] With Belostoma, the odor- abdomen. They open externally between tha 



Iferous glands consist of two pretty long caecal coxae of the posterior legs. See Leidy, loc. cit. p. 



tubes situated in the metathorax, beneath the other 64. — Ed. 

 viscera, and extending into the anterior part of the 



