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TEXT-BOOK OF ENTOMOLOGY 



The wax-glands in the honey-bee are scale-shaped organs situated 

 on the under side of the four last abdominal segments (Fig. 355). 

 These secrete the wax, which appears as whitish scales, and secretion 

 is only possible when, the bees have sufficient honey and pollen. 

 The wax is secreted by the hypoderrnal cells rather than by glands 

 within the abdominal cavity ; the wax traverses the cuticular layer, 

 and accumulates on its outer surface (Carlet). According to Fritz 

 Mtiller, in the stingless bees (Trigona) which he observed, the wax- 



FIG. 355. Wax disks of social bees: , Apis mellifica, worker; b, do., queen ; c, Melipona. 

 worker; d, Bombus, worker. From Insect Life, U. S. Dept. Agr. 



glands are situated on the back of the abdomen, but Ihering states 

 that in many species of Trigona and Melipona there are also slightly 

 developed wax-organs on the ventral side. 



It has been found that certain caterpillars secrete wax. Thus the cells 

 of the Tortrix of the fir (Eetinia resinella) formed of resin are lined with 

 wax, as on dissolving away the resin with alcohol, Dr. Knaggs found a slight 

 film of wax ; also a secretion of wax has been detected in the larva of a butterfly 

 (Parnassius apollo). The bodies of certain saw-fly larvae are covered with a 

 white powdery secretion, while the remarkable larva of a Selandria is clothed 

 with snow-white, long, flocculent, waxy masses, nearly concealing the body 

 (Fig. 356). 



h. "Honey-dew" or wax-glands of Aphids 



The so-called "honey -dew" of Aphids which oozes from two wart- 

 like tubercles or tubes situated near the end of the body, is secreted 

 by hypodermal unicellular glands which open into a modification of 

 a pore-canal, the tube itself being an outgrowth of the cuticula. 



Witlaczil states that both in the " honey " tubes and in the body beneath, the 

 sugary matter exists in cells of the connective tissue in the form of granules. 

 "These large ' sugar -cells ' in contact with the air undergo destruction, while 

 the sugar crystallizes into needles, and thus each cell is transformed into a 

 radiated crystalline mass." 



