214 HYMENOPTERA. 



All these characters show that the saw-fly isi, a degrade^ 

 Hymenopter. 



The antennffi are not elbowed ; are rather short and simple, 

 clavate, but in rare instances fissured or feathered. The ab- 

 domen consists, usuall}^, of eight external segments, the two 

 last being aborted on the under side, owing to the great develop- 

 ment of the ovipositor. The ovipositor or "saw" (compare 

 Fig. 24) consists of two lamell®, the lower edge of which is 

 toothed and fits in a groove in the under side of the upper one, 

 which is toothed above, both protected by the usual sheath-like 

 stylets. On pressing, says Lacaze-Duthiers, the end of the 

 abdomen, we see the saw depressed, leave the direction of 

 the axis of the body, and become perpendicular. Hy this 

 movement the saw, which both cuts and pierces, makes a gash 

 in the soft part of the leaf where it deposits its eggs. 



The eggs are laid more commonly near the ribs of the leaf, 

 in a series of slits, each slit containing but a single egg, 

 "Some species, on the other hand, introduce their eggs by 

 means of their saws into the edges of leaves (Nematus conju^ 

 gatus Dahlb.), and others beneath the longitudinal ribs of the 

 leaves. A few, indeed, merely fasten their eggs upon the outer 

 surface of the leaves (^Nematus grossularice, etc.), attaching them 

 together like a string of beads (Reaumur, vol. v, plate 10, fig. 

 8), whilst a few place them in a mass on the surface of the leaf 

 (ibid, plate 11, figs. 8, 9)." (Westwood.) The irritation set up 

 by the saws in the wounded leaf, causes a flow of sap which is 

 stated by Westwood to be imbibed by the egg, so that it swells 

 gradually to twice its original size. It is known that the eggs- 

 of ants increase in size as the embryo develops, and M^e would 



copy his diagram (Fig. 144), showing the venation of the wing (compare Fig. 29' 

 and our nomenclature), with the explanation of parts given by him. 



a, stigma; 6, costa or costal margin; c, apical margin; rf, costal and post- 

 costal veins; e, externomedial; /, ff, anal; h, posterior margin; i, marginal vein; 

 j, siibmarginal vein; J:, first, second, and third (transverse) submarginal nervures; 

 Z, recurrent nervures (discoidal); m, discoidal vein; n, first and second inner njii- 

 cal or submarginal nervures. Bullae or clear spots, on the veins or nervures, with 

 bullar or clear lines crossing them. 1,2, marginal or radial cells ; 3, 4, 5, 0, submar- 

 ginal or cubital cells ; 7, 8, 9, discoidal cells ; 10, costal cell ; 11, 12, brachial or me- 

 dial cells; 13, 14, inner and outer apical cells. (Hinder cells, Hartig. Cellule du 

 limbe, St. Farg.) Xo. 11 is sometimes the medial, and Nos. 12 and 13 the submedial 

 cells; Nos. 9 and 14 the apical cells; Nos. 7 and 13 discoidal; Nos. 10, 11, 12, 15, the 

 first, second, third and fourth biMchial cells; 15, lanceolate cell. 1, open; 2, con- 

 tracted; 3, petiolate; 4, subcontracted; 5, with oblique cross nervure; U, withi 

 straight cross nervure. 



