76 



The Naturalist. 



semicircular form, called the tegula or base-cover, an appendage 

 peculiar to the Lepidoptera and HymenopUra, but in the former 

 it attains a considerable size.^ The mesothorax also bears a small quad- 

 rangular slightly convex plate, termed the scutellum. In many 

 species of Ichneumonidce^ this is of a different colour to the remainder 

 of the insect ; thus, a black or dark ichneumon sometimes possesses a 

 bright yellow scutellum. Immediately beyond the scutellum is a 

 narrow, slightly lunar shaped segment, appropriately called the post- 

 scutellum. 



The appendages of the metathorax are the posterior pair of wings 

 and the third or hinder pair of legs. At the extremity of the abdomen 

 will be observed a long bristle-like appendage, which readily splita 

 into three parts. This is called the ovipositor, and as it is an important 

 organ, I will return to it shortly. 



The mesothorax, as I before remarked, bears the anterior pair of 

 wings. These appendages are divided into perfect cells by nervurea 

 or wing rays. At first glance, the costal margin appears considerably 

 thickened, but a closer examination shows that the costal and sub- 

 costal nervures run exactly parallel, no vacant space being included 

 between them, hence the absence of a sub-costal cell.^ About three 

 quarters of the distance along the costa is situate a small dark 

 triangular spot called the stigma. The whole of the wing membrane 

 is studded with innumerable spines, which all point outward towards- 

 the tip. Some idea of their numbers may be gathered from the fact 

 that I have counted as many as fifty of these bristles in the areolet. 

 I likewise took the under wing of a small Pimpla^ and commencing at 

 the tip and proceeding along the hind margin to the base, I found 

 there were four hundred and sixty-four spines in the included space. 



So much for the wings : the legs take our attention nest. These 

 are pretty much the same as in other insects, are long and adapted for 

 speed. They consist of five parts (1), the coxa or hip, which 

 connects the leg with the body ; (2), the trochanter or scapula, which 

 apparently is made up of two parts ; ^ (3), the femur or humerus ; (4), 

 the tibia, and (5), the tarsus, which again consists of five joints, the 

 last being terminated by two claws. Such is the general external 

 appearance of an ichneumon, but before dismissing this part of the 

 subjectj I will say a few words about the ovipositor. This formidably 

 instrument, common to the females of all parasitical hymenoptera, and 



3 Kirby and Spence's Introduetion to Entomology. 



4= Westw. Class. Vol. 2, p. 139. 

 5 Kirby and Spence's Introduction t© Entomology. 



