INTRODUCTION. XXXlll 



notum, their sides as the pleurae, and the lower surface as the sternum. 

 The prothorax is very short, usually transverse, extending laterally to the 

 radix. Its pleurae bear grooves, in which the front femora rest during 

 repose, and their margins are known as the epomiae. The mesothorax is 

 usually as broad as, or a little broader than, the head, and is divided into 

 two distinct sections, called the scutum or disc, which is produced into the 

 prominent Scutellum. This is much smaller than the disc, and is situated 

 at the base of the mesothorax, between the hind pair of wings. It is 

 generally somewhat convex, triangular, with erect pdosity. At its apex is 

 a small prominence designated the post-scutellum. It will be noticed thai 

 the post scutellum forms the centre of a transverse, almost linear, band 

 which, laterally, bears the hind wings. This is the true metanotum, which 

 is not referred to in descriptions. The convex portion between it and the 

 petiole has been proved by micro-anatomy to be the true first abdominal 

 segment, and is superincumbent upon the true metanotum, which will be 

 found to laterally extend back to, and bear, the hind coxae. This portion 

 is termed the propodeum by Saunders, but its old collective name, meta- 

 thorax, embracing both the true metathorax and the superincumbent 

 abdominal segment, is here, for the sake of convenience, retained. The 

 region of the scutellum is the centre of the insect, consequently the 

 prothorax is at the apex of the mesothorax and the abdomen at the apex 

 of the metathorax. 



Tlie Abdomen is connected with the thorax by a more or less distinctly 

 constricted stem, called the petiole. This is the base of the first ab- 

 dominal segment, which towards its apex becomes more or less explanate, 

 and is thence known as the post-petiole, usually bearing distinctive sculp- 

 ture. The second segment before its base is often deeply impressed 

 sulciformly at the sides, and these impressions are the gastrocaeli, their 

 apical margins being the thyridii. There are eight dorsal segments, of 

 which the pygidium is rarely visible, being retracted beneath the seventh 

 segment. There are also eight ventral segments in the male, but only six 

 in the female. These are often longitudinally plicate, in the centre, after 

 death, owing to the contraction of the soft tissues upon desiccation. The 

 apical ventral segment is the hypopygium, and is of variable form and 

 extent, often covering the base of the terebra, which is composed of the 

 central, true ovipositor or spicula and its two lateral, protecting valvulae or 

 sheaths. The length of the terebra varies from twice that of the insect to 

 barely visible beyond the apex of the hypopygium. 



The Legs, so distinctive in many groups of insects, are here dis- 

 appointingly uniform in structure, being nearly invariably long and slender 

 with few modifications. The basal joint or coxa, however, often bears a 

 little tuft of dense pilosity known as the scopula, is sometimes dentately 

 mucronate or obliquely cristate, and is always more or less closely punc- 

 tate. The next two joints compose the trochanter, which is followed by 

 the elongate and rarely dentate femur. The sometimes s[)inLilose or 

 intumescent tibia is articulated to the ai)ex of the femur, and is followed 

 by the five-jointed tarsus. The onyches are occasionally internally 

 pectinate or furnished with comb-like bristles, and the basal joint of the 

 front tarsi is excised beneath, forming with the calcaria, or apital tibial 

 spurs, a beautiful apparatus for cleansing the antennae, t\;c. The anterior 

 legs are the two front pairs collectively ; the posterior the two hind pairs 

 collectively. The front and hind legs each comprise but a single pair. 



