Z. P. Mi 



21* 



Art. XXIII. — On the Species of Platygaster, §-c. By 

 Francis Walker. 



- The Oxyurites or Proctotrupites, a tribe of parasitic 

 Hymenoptera, of which this family forms a part, are an 

 extensive group, and have a greater variety of structure than 

 the Chalcidites or Ichneumonites, though inferior in number, 

 and less attractive, from their usual black colour and minute 

 size. They are distinguished by the shape of the ovipositor, 

 which is flexible, retractile, and tubiform, like that of the 

 Chrysites. They have most affinity to the Cynipites, but 

 these are at once known by the peculiar conformation of the 

 wing-nervures. 



In this family, as in Scelio and Teleas, and some other 

 genera, the segments of the abdomen above form a rim around 

 those below. The wing nervures are very generally obsolete ; 

 but in some species a single nervure proceeds from below the 

 border, and ends in a round dot before the middle of the wing, 

 and in two instances is forked. 



The two groups into which they have been divided by the 

 form of the scutellum, may also be generally distinguished 

 from each other by several other slight differences. The first 

 group, comprising the species with the scutellum more or less 

 lengthened and pointed behind, has the body generally hairy, 

 the female antennae clubbed, the thorax smooth and shining, 

 the abdomen of the female varying much in form, the second 

 segment with two impressions at the base, the wings often 

 fringed : while in the second group, or the species having the 

 scutellum formed as a tubercle, the body is seldom hairy, the 

 tips of the antennae are very slightly dilated, the thorax is 

 punctured, the abdomen has usually the same shape in both 

 sexes, with the second segment furrowed at the base, and the 

 wings are seldom fringed. 



The sexes are often alike in shape, but the males may be 

 easily distinguished from the females by their antennae, in 

 which the fourth joint is much more developed, and the tenth 

 joint longer, and moje pointed. 



The colour is generally black, that of the legs and antennae 



NO. III. VOL. III. F F 



