152 MODERN CLASSIFICATION OF INSECTS. 
Bracones, and Bassi of Gravenhorst and Esenbeck, and founded prin- 
cipally on the variations in the number of joints of the palpi, a character 
which has since been proved to be of too slight a value amongst 
the Adsciti. Mr. Haliday, in his systematic distribution of the Adsciti 
(Lntom. Mag. vol. i. p. 261. 1833.), divided them primarily thus : — 
* Abdomen sub pectus incurvatile. G. Aphidius. 
** Abdomen haud penitus incurvatile. 
1. Areola antica disci contigua completa. G. Sigalphus, &e. 
2. Areola antica disci remota vel incom- G. Microgaster, Bracon, Alysia, 
pleta. Agathis, Leiophron, &c. 
Mr. Stephens (Jilustr. Brit. Ent. vol. vii. p. 117. 1835.), retaining 
the number of joints in the maxillary palpi as the leading character, 
has separated the Ichneumonidz into four families: 1. Ichneumonide, 
2. Braconidze (max. palpi 5-jointed); 3. Alysiidz (m. p. 6-jointed); and 
4. Aphidiidz (m. p. 4-jointed). Still more recently, Mr. Haliday (ne. 
Mag. No. 23. 1838) has divided them into five families, including, 
1. Evaniidee; 2. Ichneumonide ; 3. Agriotypide; 4. Braconidee; and 5. 
Aphidiidze, founded upon the nature of the connexion between the 2 and 
3 dorsal segments of the abdomen, and the outer discoidal cell of the 
fore-wings. On reviewing these arrangements, it appears to me that it 
will be far more natural to retain the binary division of Ichneumones 
genuini and adsciti; and such is the opinion also of my friend M. 
Wesmael, who characterises the former (Ichneumonides) by having 
two recurrent nerves, and the latter, which he names Braconides, by 
having only one recurrent nerve. 
The sub-family Ichneumonides comprises the largest species of the 
family; and is not only distinguished by having two recurrent nerves, 
but also by having the nerve which separates the first cubital or sub- 
marginal cell from the external discoidal cell, either entirely or nearly 
ubliterated, whereby these two cells become confluent. No genuine 
Ichneumon with perfect wings has yet been described in which this 
structure does not exist. Moreover, the second cubital or sub-mar- 
ginal cell (the area specularis of Fallen) is very greatly reduced in 
size, being sometimes petiolated, but often entirely obsolete. It is in 
this minute area, or in the space which it should typically occupy, that 
the second recurrent nerve is inserted: M. Wesmael also adds the 
existence of an articulation between the second and third dorsal seg- 
ments of the abdomen. 
Amongst the Ichneumonides may be noticed the genera Pimpla, in 
which the ovipositor and its sheaths are often greatly elongated, being 
