ABDOMINAL APPENDAGES. 



623 



bryo Insects exhibit similar structures. Finally there are 

 certain structures borne at the hinder end of the abdomen 

 which are regarded by some, though there is no general 

 agreement on this point, as of the nature of limbs. Amongst 

 these are (i) the cercopcds 

 or cerci anales, usually seg- 

 mented processes, tactile in 

 function, which both in 

 their appearance and their 

 use resemble antennae ; (ii) 

 the three, paired elements 

 of the ovipositor, which is 

 developed in the females of 

 certain Thysanura, Orthop- 

 tera, Odonata, Hemiptera, 

 Physapoda and Hymeno- 

 ptera, in which last named 

 order the ovipositor is often 

 modified to form a saw or a 

 sting. It is formed, gen- 

 erally speaking, from 

 processes of the seventh, 

 eighth and ninth abdominal 

 segments, though in many 

 cases it appears that the 

 posterior two pair of pro- 

 cesses arise together from 

 the ninth (Fig. 379) ; (iii) 

 certain claspers and other 

 processes connected with 

 the male hit remittent 

 organ and with copulation 

 which seem to have an 

 origin similar to that of 

 the component parts of the ovipositor with whose claim to be 

 regarded as true appendages theirs must stand or fall. 



The Alimentary Canal. Embryologically the alimentary 

 canal is divided into (a) the stomodaeum or fore-gut which givrs 

 rise to (i) the mouth and pharynx, (ii) the oesophagus (Fig. 380), 

 (iii) the crop, (iv) the proventriculus or gizzard ; (b) the mesen- 



FIG. 380. Digestive apparatus of A/H'S nn-llifira 

 (after Leon Dufour). Sp salivary glands ; Oe oeso- 

 phagus with crop-like dilatation ; M ehylitic ven- 

 tricle ; Re malpighian vessels ; R rectum with 

 so-called rectal glands ; G. Dr poison glands. 



