in most of the other orders, and all the accessory parts are strongly developed.
These, and other parts of the oral appendages, are represented on Pl. XXVI.
Figs. 15 and 16, the maxilla and labium of a Tenthredo—Fig. 15, the maxilla;—l i, the inner lobe, and l e, the exterior lobe representing the galea; c, the stipes; d, the cardo; p, the palpus (six-jointed.)—Fig. 16, the labium;—m n, the mentum; l 2, the trilobed labium; l p, the labial palpus.
Fig. 17, the maxillæ and labrum of Sirex juvencus (male;) m x, maxillæ; m x p, maxillary palpi; a, the fulcrum; m n, the mentum; l 2, the lower lip; l p, the labial palpi.
Figs. 18-23, oral organs of a Pimpla.—Fig. 18, the head seen from the front;—a, antenna; e e, the eyes; o, ocelli; l i, the minute upper lip; m, the mandibles; m x p, maxillary palpi; l p, labial palpi.—Fig. 19, head seen from behind;—m n, the mentum; l 2, the labium; m x, the maxillæ; m x p, the maxillary palpi; l p, labial palpi.—Fig. 20, labrum;—l 1, the appendiculata (Kirby and Spence.)—Fig. 21, one of the bifid mandibles Fig. 22, maxilla;—l e, external lobe; l i, internal lobe; c, stipes; d, cardo; p, maxillary
palpus.—Fig. 23, lower lip;—a, fulcrum; m n, mentum;
l 2, labium; l p, labial palpi.
The variations of the antennæ are too numerous to be specified in this place. The number of joints is from three (their amount in Hylotoma) to about fifty. These multiarticulate antennæ are chiefly to be found among the Ichneumonidæ, whose economy renders it necessary that they should be very flexible for the
purpose of exploring the holes and crevices into which they introduce their eggs. In some instances the antennæ are bipectinated; in other cases (as in Cryptus) they appear double, the third joint being long and furcate. They are often very dissimilar in
