[Reprinted from Wisconsin Natural History Society's Bulletins Nos. I and 2— Vol. IV — (New Series) 



April, 1906.] 



THE CHEMICAL NATURE OF SOME INSECT SECRETIONS, 



BV A. L. MELANDER AND C. T. BRUES. 



In this paper we have attempted to give in addition to some 

 original observations, a brief resume of what is definitely knov^n 

 regarding the general chemistry of the odors of insects and 

 myriapods. 



Most of the odorous secretions of insects are the products of 

 highly specialized glands which derive from the blood the founda- 

 tion for their work. An exception to this, however, is seen in the 

 fat occurring associated with the chitinous skeleton of insects. 

 Of the glandular secretions one may define two categories: those 

 used by the insect directlv in its own metabolism, and those of 

 more indirect use as an odorous character and developed to suit 

 peculiar conditions of environment or habits. As the first group 

 includes products found elsewhere throughout the animal 

 kingdom, c. g., the salivary, digestive, and excretory fluids, all 

 secreted by portions of the alimentary tract, we shall pass them 

 by to consider those substances more or less peculiar to insects 

 themselves. These products are of two kinds: defensive, m;alo- 

 dorous, highly volatile liquids developed principally to repel 

 predaceous enemies ; and alluring, sweet-scented or sweet-tasting 

 fluids used to attract the two sexes of a species or the individuals 

 of a community, or even to insure protection by other species as 

 is the case with many myrmecophilous insects. 



We are not aware that anyone has ever attempted to classify 

 insect odors, but Kerner and Oliver ('95) p. 199, have divided the 

 odors of flowers into the following groups: indoloid, aminoid, 

 parafflnoid, benzoloid and terpenoid. As other scents seem to be 

 developed in insects and some to be lacking, this classification is 

 not wholly suited to our purpose. Accordingly, we have used the 

 following outline in the absence of a more satisfactory one. It 

 includes six rather heterogeneous groups: Ethereal and Ben- 

 zoloid, Indoloid, Isonitrile, A^egetable extracts. Acid, Alkaline. 



ETHKREAI< AND BENZOLOID. 



The European bugs of the genus Pyrrhocoris secrete a sw^eet 

 smelling and pleasant tasting etheral liquid, according to Mayer 

 ('74). The Texan ant. Camponotus maculatus sansabcauus, has 

 a marked scent resembling a combination of butyric and valer 



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