a Family of the Hymenoptera Heterogyna. 197 



with one marginal and three submarginal cells, which vary in form in 

 the species, and one recurrent nervure, which is inserted about the 

 middle of the second submarginal cell *. 



Ze^s varying in length in the species: cod:;^ large, not deeply excavated above: 

 trochanters small, triangular : femora and tihicp cylindrical, all the latter 

 with a single calcar at their apex, which is usually dilated at the base : 

 tarsi long and slender, the basal joint the most robust and the longest, 

 the remainder decreasing in length, excepting the terminal one, which 

 is a little longer than the penultimate : claws armed with a minute 

 tooth just within the apex, and furnished with a small pulvillus within 

 their fork. 



Abdomen cylindrical, slightly curved, the segments frequently slightly con- 

 stricted, the basal one forming a variously constructed peduncle, oc- 

 casionally either flat or concave above, but most frequently transversely 

 convex, and always separated from the following by a deep incisure. 

 Penultimate and antepenultimate segments subequal, and the terminal 

 one strictly compressed vertically at its apex, where it is profoundly 

 emarginate. — The male sexual organ usually protruding in the form of 

 a deeply canaliculated and emarginated plate or two acuminated com- 

 pressed and curved spines f. 



Type of the genus, Labidus Latreillii, Jurine. 



As far as yet discovered, the insects of this genus are all from the 

 New World, and I believe inter- or subtropical. Their habits have 

 not been observed, nor have their females been yet detected with cer- 

 tainty, although it is perhaps probable that the insects I describe 

 below as such may be so ; at all events they have a decidedly close 

 affinity to the present genus. The arguments whereby I support 

 this view will be exhibited in connexion with the insects themselves. 

 Although three species of this genus have been described, they have 

 been attributed to the same, but that they are not identical will be 

 shown in the synonymy. As the first species was described by a 

 patronymic, I have followed this example, and have dedicated them 

 all to individuals distinguished for their attachment to the Hyme- 

 noptera. 



* The larger relative proportions of the wings in this genus is shown by a 

 comparison of their expansion with the length of the insect; I have therefore 

 always given both these admeasurements. 



t The form of this organ I regret I cannot examine, for the sake of com- 

 parison with those of the other genera of this remarkable family. It must 

 necessarily very much differ from the others, even more than they do inter 

 se, from the peculiar structure of the apex of the terminal segment ; but I 

 suspect it would most resemble that of Rhogmus, with which the genus 

 agrees in the vertical incision of the dorsal portion of the terminal seg- 

 ment. 



