101 
PLATES LXXIV and LXXV. 
ILLUSTRATIONS OF SOME SPECIES OP AUSTRALIAN THYNNIDEOUS 
INSECTS. 
The recent monographs of Dr. King and M. Guerin-Meneville 
upon the Genus Thynnus of Fabrlcius, and the different results at 
■which these distinguished Hymenopterologists have arrived respect¬ 
ing the generic arrangement of these insects, render the observation 
of every fact, tending to determine the question at issue, absolutely 
necessary; and no one circumstance has hitherto been shown to be 
more important than the exact discrimination of the sexes of the 
different species, since by this means not only are we prevented 
from forming separate genera for the reception of the two sexes of 
the same species, but we are thereby enabled to trace the value of 
the modifications of structure which may have been already, or 
which ought hereafter to be adopted as the characteristics of the 
several groups into which these insects have been or are divided. 
As a group, these insects possess an interesting geographical dis¬ 
tribution, being only found in Australasia and South America. 
The species from the latter country are rare in our English cabinets, 
whilst Dr. Klug describes not fewer than 40 species ; whereas our 
cabinets are very rich in the New Holland species, which are equally 
rare in the continental collections. 
By the kindness of several friends I am enabled to give represen¬ 
tations of both the sexes of five Australian species. 
In order, however, to enable such of my subscribers as do not 
possess the “ Voyage de la Coquille,” (in the Zoological portion of 
which M. Guerin published his chief memoir on these insects) to 
enter more effectually upon the consideration of the question of the 
generic distribution of these insects, I here copy from that work 
such portion of the tabular synopsis of the genera of the Hymenop- 
tera Heterogyna, as relates to the insects in question. 
1. Abdomen des m Meg cylindrique, termini infdrieurement par une grande epine recourb^e 
ca haut. . . . (Genera Methoca, Myzine ct) Rhagigaster, Guer, 
2. Abdomen dcs mAles aplati, n’ayant point a Uextrdmit^ d’^pine recourbe'e vers le haut. 
a Mandibules tridentecs. 
* Les deux nervures recurrentes aboutissant aux 2mc et 3mo cellules cubitales. j 
G. Telephoromyia, Guer, 
** Les deux nervuics recurrentes aboutissant ala seconde 
cellule cubitale. . . G. Tachyptcrus, Guer. 
