NO. 2 RECOGNITION AMONG INSECTS McINDOO 65 



(b) INVAGINATED POUCH OF HONEY-BEE 



Under this heading belongs the description of the scent-producing 

 organ of the honey-bee, but since a brief review of it has already 

 been given on pages 36 to 37, further remarks are unnecessary. 



C. Summary of Scent-Producing Organs of Insects 



In the first part of this summary the scent-producing organs are 

 grouped on the basis of their devices for disseminating the odors and 

 for storing the secretion, while in the second part they are grouped 

 according to the order of the insects being discussed. 



A review of the literature shows that the substance produced 

 by any scent-producing organ is secreted by unicellular glands which 

 so far as known are modified hypodermal cells. On this point 

 Gazagnaire (1886) remarks that glandular cells of hypodermal origin 

 are widely distributed in insects. They secrete the various fluids 

 exuding through the chitin, and since their histology is so similar 

 it might be admitted that they have the same general structure. For 

 description, scent-producing organs may be divided into five types 

 based on their devices for disseminating the odor and for storing the 

 secretion as follows: (i) No special device for disseminating the 

 odor or storing the secretion; (2) gland cells associated with hairs 

 and scales as a means of scattering the odor more effectively; (3) 

 " evaginable " sacs lined with hairs connected with gland cells as a 

 device for storing the secretion and distributing the odor ; (4) articu- 

 lar membranes serving as pouches for storing and preventing a too 

 rapid evaporation of the secretion; (5) specialized tubes and sacs 

 acting as reservoirs for storing and discharging the secretion. 



The first type is the simplest of all five types. It is best repre- 

 sented as unicellular glands uniformly distributed over the entire 

 body surface as found in several beetles. In this type of scent- 

 producing organ the secretion passes through the chitinous tubes to 

 the exterior where it spreads over the surface of the chitin sur- 

 rounding the exits of the tubes. 



In regard to spreading the secretion over a wider area, the second 

 type is much more highly developed than is the first type. This is 

 accomplished in most cases by the secretion spreading over the sur- 

 faces of many large hairs arranged in tufts which may be expanded 

 into a fan-shaped figure. In the second type the secretion from the 

 gland cells passes into the hairs and scales and then spreads over their 

 surfaces, whereby the odor from the secretion is more effectively 

 disseminated. 



