214 HTMENOPTERA. 



All these characters show that the saw-fly is a degraded 

 Hymenopter. 



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

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

 domen consists, usually, 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 lamelloe, 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. B}^ this 

 movement the saw, which both cuts and pierces, malves 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 

 leaA'es. A few, indeed, merely fasten their eggs upon the outer 

 surface of the leaves {Nematus grossidaricr, 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 einbryo develops, and we would 



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

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



a, stigma; h, costa or costal margin; <;, apical margin; </, costal and post- 

 costal veins; «, externoniedial; /, </, anal; h, posterior margin; i, marginal vein; 

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

 /, recurrent nervures (discoidal); to, discoidid vein; 71, first and second inner api- 

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

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

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

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

 linibe, St. Farg.) Xo. 11 is sometimes the medial, and Nos. 12 and 13 the .'ubmedial 

 cell.-. ; Nos. 9 and 14 the apical cells ; Nos. 7 and 13 discoidal ; Nos. 10, 11, 12, 1.5, the 

 first, second, third and fourth brachial cells; 1.5, lanceolate cell. 1, open; 2, con- 

 tracted; 3, petiolate; 4, subcontracted; 5, with oblique cross nervure; 0, with 

 straight cross nervure. 



