ACULEATA 



withdrawn into the body in a direct manner so as to be entirely 

 internal, whereas in the I'arasitica it is not withdrawn in this 

 manner, but remains truly an external organ, though in numerous 

 cases concealed by a process of torsion of the terminal seg- 

 ments. If this were done it might be found possible to divide 

 the great group thus formed into two divisions characterised by 

 the fact that the ovipositor in one retains its function, the egg 



Fig. 2. — Diagram of iipper sur- 

 face of Priocnemis ajfinis 9 , 

 Pompilidae. o, ocelli ; 7J^, 

 pronotuni ; 7J^, mesonotum ; 

 B^, sciitellum of mesonotnni ; 

 B^, post-scutelluni or middle 

 part of metanotum ; h^, propo- 

 deum or median segment (see 

 vol. V. p. 491) ; Js'^, combing 

 hairs, pecten, of front foot: C, 

 first segment of abdomen, here 

 not forming a pedicel or staik : 

 Z)^, coxa; />^, trochanter; D'-^, 

 femnr ; JJ^, calcaria or spurs 

 of liind leg: 1 to 15, nerv- 

 nres of wings, viz. 1, costal ; 

 2, post -costal ; 3, median ; 

 4, posterior ; 5, stigma ; 

 6, marginal ; 7, upper 

 basal ; 8, lower basal ; 9, 9, 

 cubital ; 10, tlie three sub- 

 marginal ; 11, lirst recurrent ; 

 12, second recurrent; ];% 

 anterior of hind wing ; 1-), 

 median ; 15, posterior : I to 

 XI, the cells, viz. I, upper 

 basal ; II, lower basal ; III, 

 marginal ; IV, V, \l, first, 

 second and third sub-mar- 

 ginal ; VII, first discoidal ; 

 VIII, third discoidal ; IX, 

 second discoidal ; X, first 

 apical ; XI, second apical. 



passing through it (Proctotrypidae and Tubulifera), while in the 

 other the organ in question serves as a weapon of offence and 

 defence, and does not act as a true ovipositor, the egg escaping 

 at its base. It would, however, be premature to adopt so revolu- 

 tionary a course until the comparative anatomy of the organs 

 concerned shall have received a much greater share of attention.^ 

 We have dealt with the external anatomy of Hymenoptera in 



1 For new views on this subject see note on p. 602. 



