lo HYMENOPTERA ACULEATA. 



•pvostcrnura receives the front pair of legs. In the mesothorax 

 the votum or scutum is largely developed, as well as the 

 plcurse; the scuiellumis variablein size, and situated behind it. 

 Very important characters lie in the sculpture of the meso- 

 noium and Tnesopleune ; the mesothorax bears the first pair 

 of wings, the extreme base of which are covered by two 

 little concave plates called the tegulae, and the second pair 

 of legs. The metafhorax proper is short, its summit form- 

 ing the fostscutellum, but behind the ■postsculellum is 

 often another strip widening laterally into a triangular 

 pleural expansion ; this segment bears the posterior wings 

 and legs; behind this is the propodeum which varies much 

 in form, in some of the ants and in the genus Ny ss on it heara 

 spines, but as a mile it is rounded posteriorly ; it often 

 bears at its base an enclosed area, which affords valuable 

 characters ; in fact, the sculpture of the metanotiim, 

 metapleurai and propodeum is generally of high specific 

 importance. 



The wings are membranous, and vary much in their 

 ueuration, the arrangement of which is often of great value 

 for classificational characters. There are in the anterior 

 wings four main nervures extending from the base towards 

 the apex : the costal nervure, which forms the anterior 

 margin of the wing, the postcostal, which runs close and 

 parallel to it; the median, which is situated about the middle 

 of the wing ; and the postmor, which lies between this last 

 and the posterior edge of the wing. The costal and post- 

 costal nervures terminate in the stigma a dark incrassation 

 on the anterior margin of the wing, beyond which is the 

 minjinal cell enclosed by the marginal nervure, which in 

 rare cases has an appendix. From the apex or sometimes 

 nearer the middle of the postcostal nervure is emitted a 

 transverse nervure called the upper basal nervure. This 

 connects the postcostal with the median ; the median is 

 connected with the posterior by another transverse nervure 

 called the lo!oer basal nervure. These two transverse 

 nervures are often united. The cells enclosed by these basal 



