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TEXT-BOOK OF ENTOMOLOGY 



appear to become very easily loosened and detached, and they prob- 

 ably, when brought into contact with the skin of any aggressor, 

 burrow underneath, and are probably in part the cause of the con- 

 tinual itching and annoyance occasioned by these creatures. It will 

 be seen by reference to Fig. 213, e', that the body of the spine is 

 spherical, with one large, elongated, conical spine arising from it, the 

 spherical base being beset with a number of minute, somewhat obtuse 

 spinules. 



Glandular hairs and spines. In some insects occur fine, minute, 

 hollow setae from which exude, perhaps through pore-canals of ex- 



a 



b 



a A 



FIG. 214. Glandular hairs of caterpillars. A, Daxylophitt aiitjtiiini : a. of l>oily ; b, of head ; 

 e, of prothoraeie shield. B, < ', /<//*/</ fi-ii-nlor : a, on body; b, on abdominal k-^s. (', Sr/ii-i/rn 

 ijiin>'<(' : <i, from third thoracic segment ; b, from larva stage II ; c, simple seta- from minute warts. 



treme fineness, droplets of a clear watery or plasma-like sticky fluid. 

 The club-shaped tenent hairs of the feet of Collembola, and the hairs 

 fringing the feet of Diptera, are modified glandular hairs. Here 

 they serve to give out a sticky fluid enabling the insect to walk on 

 smooth surfaces ; they end in a vesicle-like bulbous expansion, which 

 may contain numerous pore-canals. Those of caterpillars were first 

 noticed by Zeller, and Dimmock has particularly described those of 



