32 THE ENTOMOLOGIST. 
the abdomen, length of ovipositor or aculeus, and form of the 
areolet (second cubital areola) if present. 
The families of this group may be briefly defined as follows, 
always bearing in mind that most of these families possess some 
species or genera which at first sight might be placed in some 
other family ; for instance, in Tryphonide we find species with a 
pentagonal areolet, as Adelognathus and some of the Orthocentrus, 
whilst Orthocentrus anomalus has an aculeus as long as the 
abdomen. And in the Cryptide the genus Stilpnus has the 
aculeus not projecting. 
A. The 2ud segment of the abdomen avouw 
four times as long as the 3rd. - - Ham. 3. AGRIOTOPIDE. 
B. ‘The 2nd segment not more than twice as 
long as the 3rd, generally subequal. 
a. Areolet of wings a regular pentagon or 
quadrate, the external nervure some- 
times pellucid or wanting. 
* Mesosternum not separated from the meso- 
pleura by a depression (sometimes a 
very short depression present). Aculeus 
very short, or hidden. ; - Fam. 1. IcHNeEUMONIDA. 
** Mesosternum separated from the meso- 
pleura by a distinct depression, some- 
times complete (female sometimes ap- 
terous); aculeus projecting sometimes as 
long as the abdomen. . - - Fam. 2. CRYyprip&. 
b. Areolet small, deltoid, or none. 
+ Abdomen depressed, rarely subcompressed 
at the apex. 
t Aculeus of female very short, often hidden. Fam. 5. TryPHONIDs. 
tt Aculeus of female long, generally more than 
half the length of the abdomen = Fam. 6. PrmMpiip2. 
++ Abdomen more or less compressed, often 
very much so; aculeus sometimes hid- 
den, rarely as long as the abdomen. - Fam. 4. OpHIONIDS. 
A better idea of the generalities of these families can of course 
be obtained by the beginner from the examination of some 
typical collection, or, failing this, from Ratzeburg’s, Curtis’s, or 
Vollenhoven’s figures. The three excellent plates in Vollenhoven’s 
‘Schetsen ten Gebruike bij de Studie der Hymenoptera,’ Part 1, 
