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TEST-BOOK OF ENTOMOLOGY 



secrete the poison. The poison is diluted by the secretion of the 

 salivary lobes, and the two efferent ducts, one from each set of 



FIG. 851. A, median section of head, showing (<7) the venomo-salivary duct, with its inser- 

 tion in (hy) the hypopharynx; cb, brain; below is the pharyngeal pump, leading- from (,) the 

 oesophagus; Ire, base of labrum-epipharynx ; m, muscle; n, commissure (other parts removed). 

 B, the venomo-salivary duct, showing its bifurcation, and the three glands on one of its branches ; 

 pg, poison gland ; xy, the upper of the two salivary glands, ti, the bifurcation of the duct, with its 

 nucleated hypodermis. After Macloskie. 



glands, " carry forward and commingle the venomo-salivary products 

 in the main duct ; and the stream is then carried by the main duct 

 to the reservoir at the base of the hypopharynx." 



/. Adhesive or cement-glands 



Dewitz has discovered in ants and bees, in close connection with 

 the poison-glands, and like them discharging their secretion through 

 the sting, cement-glands. They arise by budding at the base of the 

 poison-glands. 



The two glands in these Hymenoptera correspond to the tubular 

 glands of the Orthoptera, which open at the base of the inner sheath 

 of the ovipositor (Fig. 299, sb), so that the secretion flows out through 

 it as the poison of bees, etc., out of the sting. The use of the secre- 

 tion of these glands is either to glue the eggs together, or to afford 

 material for the egg-case of cockroaches and Mantidse and the gummy 

 egg-case of the locusts, etc. The contents of the cement-glands serves 

 for the fixture of the eggs after deposition. In the stinging Hymen- 

 optera one of the cement-glands is an accessory gland; the other 

 becomes the poison-sac. The cement-glands are in the Hemiptera 

 only short blind sacs, in the Lepidoptera and Diptera long convo- 

 luted tubes, tubular and branched in the Coleoptera, or richly 

 branched in the Ichneumonidse and Tenthredinidse. In the cock- 

 roach there are two cement-glands, but the right one is probably 

 of no functional importance. The left one is filled with a milky 



