﻿NEARCTIC SPECIES OF GASTERUPTIIDAE — TOWNES 87 



Subfamily Aulacinab 



This is doubtless the primitive group of the family, and within it is 

 evidence of the origin of the peculiar family character of the high 

 attachment of the abdomen to the thorax: Parasitic Hymenoptera 

 with long ovipositors have evolved several methods of bracing the 

 ovipositor against bending while it is used for drilling. One of these 

 is to hold the ovipositor between the hind coxae, and in the groups 

 using this method the inner surfaces of the female hind coxae are often 

 modified to perform this function better. The usual abdominal articu- 

 lation is immediately between and slightly beyond the attachments of 

 the hind coxae, where it would interfere with the use of the hind coxae 

 for holding the ovipositor. In the groups using the hind coxae thus, 

 there is a tendency for the abdominal articulation to move upward 

 and for the coxal articulations to move backward until they are directly 

 below or slightly beyond that of the abdomen. In the Aulacinae and 

 in a few braconids (Capitonius) and ichneumonids (Certonotus, Labena, 

 and Apechoneura) the modification of both the inner surface of the 

 female hind coxa and of the position of the abdominal articulation 

 has reached an extreme. In them the inner surface of the coxa has 

 a channel or notch for the ovipositor and the abdomen is attached 

 high on the propodeum. Some Aulacinae of the genus Aulacus and 

 all the Gasteruptiinae have lost the coxal groove, but all have retained 

 the high attachment of the abdomen. The species of Aulacus with- 

 out the coxal groove are mostly those with short ovipositors, and it 

 thus appears that lack of ovipositor length made the need for coxal 

 bracing obsolete. The primitive Gasteruptiinae (Hyptiogaster, etc.) 

 have very short ovipositors and presumably theu* coxal grooves also 

 disappeared with lack of use, and the long ovipositors of the more 

 specialized Gasteruptiinae were redeveloped after the coxal grooves 

 and the habit of holding the ovipositor between the coxae were lost 

 by their short-ovipositored ancestors. 



Other evidences that the Aulaciaae are more primitive than the 

 Gasteruptiinae are the more complete venation, lack of a fold in the 

 front wing, more generalized mouth parts, less complete fusion of the 

 first and second abdominal tergites, and less extreme thoracic modifi- 

 cations. 



The subfamily has been divided into numerous genera and sub- 

 genera on venation, the number of teeth on the tarsal claws, the pres- 

 ence or absence of a tooth on the front margin of the pronotum, and 

 a few other characters. An evaluation of these divisions shows them 

 largely unnatural. Many of the venational features used for generic 

 distinctions are variable within a species, and though the other charac- 

 ters are constant and valuable for specific separation their use for 

 generic groupings often produces aggregates in which the species have 

 in common only the key characters by which they were brought 



