86 



ENTOMOLOGY 



honey with which a very little glycerine had been mixed (though Musci- 

 dse did not object to the glycerine) and Forel found that ants ate un- 

 suspectingly a mixture of honey and phosphorus until some of them 

 were killed by it. Under the same circumstances, man would be able 

 to detect the phosphorus but not the glycerine. 



Location of Gustatory Organs. As would be expected, the end- 

 organs of taste are situated near the mouth, commonly on the hypo- 

 pharynx (Fig. 128), epipharynx and maxillary palpi. On the tongue of 

 the honey bee the taste organs appear externally as short setae (Fig. 129) 

 and on the maxillae of a wasp as pits, each with a cone, or peg, project- 

 ing from its base (Figs. 130, 131). Similar taste pits and pegs were 



tb 



sc 



FIG. 128. Section through tongue of wasp, Vespa vul- 

 garis. c, cuticula; g, gland cell; h, hypodermis; n, nerve; 

 ob, gustatory bristle; ph, protecting hair; sc, sensory cell; 

 tb, tactile bristle. After WILL. 



FIG. 129. Tongue of honey 

 bee, Apis mellifera. p, protect- 

 ing bristles; s, terminal spoon; 

 /, taste setae. After WILL. 



found by Packard on the epipharynx in most of the mandibulate orders 

 of insects. 



Histology. The end-organs of taste arise from special hypodermis 

 cells, as minute setae or, more commonly, pegs, each seated in a pit, or 

 cup, and connected with a nerve fiber (Figs. 131, 132). In some cases, 

 however, it is difficult to decide whether a given organ is gustatory or 

 olfactory, owing to the similarity between these two kinds of structures. 

 In aquatic insects, indeed, the senses of taste and smell are not differen- 

 tiated, these forms having with other of the lower animals simply a 

 "chemical" sense. 



Smell. In most insects the sense of smell is highly efficient and in 

 many species it is inconceivably acute. Hosts of insects depend chiefly 

 on their olfactory powers to find food, for example many beetles, the 

 flesh flies and the flower- visiting moths; or else to discover the opposite 



