2 THE IMAGO THE HEAD. 



a well-marked section, and together have been 

 variously called Phytiphaga in allusion to their habits, 

 Sessiliventris, in allusion to the form of the abdomen, 

 and Securifera or Serrifera, after the form of the ovi- 

 positor. We may distinguish the groups as follows : 



Abdomen joined to the thorax by its entire width. Trochanters with 

 two joints. Anterior wings with a lanceolate cellule. Larvae with legs 

 on thorax only, or on thorax and abdomen. Sessiliventris* 



I. Fourth body-segment (metathorax) fissured in the middle at its 

 apex, antennas placed above the clypeus, and above the lower part of 

 the eyes. Anterior wings with at least three cubital cellules. 



A. Anterior tibiae with two spines at the apex. Prothorax email. 

 Tenthredinidce. 



B. Anterior tibiae with one spine. Prothorax large. 



1. Antennae subclavate, abdomen compressed. Middle lobe of 

 mesonotum not reaching to scutellum. Tibiae spined. Ovi- 

 positor short. Cephidce. 



2. Antennae of uniform thickness. Middle lobe of mesonotum 

 reaching to scutellum, and separated from it by a transverse 

 line. Ovipositor long. Siricidce. 



II. Fourth body-segment not fissured. Antenna? inserted below the 

 clypeus and the eyes. Ovipositor semi-spiral. Anterior wings with 

 two cubital cellules. Oryssidce. 



1st. Family. 



1. THE IMAGO. 



The Head. 



The head is always broader than long, but never 

 broader than the thorax ; it has never a globular form, 

 and usually is more or less concave behind. The eyes 

 are large, sometimes projecting, and situated on the 

 sides, rarely occupying much of the inner portion of 

 the head. They may (Sciopteryx) or may not reach to 

 near the base of the mandibles. The vertex is flat 

 with Lyda, depressed with some Tenthredina, and thick 

 and somewhat rounded with Dolerus, &c. ; the three 

 ocelli are placed in a triangle on it. The vertex has 

 sometimes well-marked sutures, as has also the front ; 

 while immediately below the ocelli there is sometimes 



* The other division of the Hymenoptera is called Petioliventris. 



