152 NATURAL ARRANGEMENT OF INSECTS. 



upon their nectar. The MutillidfB appear to enter into 

 this group, and to represent, rather than to associate with,, 

 the Formicidae. 3. The Ichneumcmides, or ichneumons, 

 where the appendage to the tail, which has hitherto been 

 a sting, now assumes the office of an ovipositor, being em- 

 ployed to deposit the eggs: the enormous developement of 

 this organ in the typical group (Pimpla, Fab.) is very 

 remarkable : this, with the parasitic habits of all these 

 insects, their very slender filiform antennae, and their 

 linear bodies, which are frequently compressed, appear 

 to separate them as a distinct tribe from our fourth di- 

 vision, the Cynipsides, including the Chalcidites, or gall 

 flies. With few exceptions, these latter are very small, 

 and even minute, insects, known at once by several 

 remarkable peculiarities : their antennae are almost al- 

 ways geniculated, and sometimes pectinated; the body 

 and limbs are usually ornamented with brilliant metallic 

 colours ; and the hind legs, like those of the coleo- 

 pterous genus Haltica, are sometimes thickened ; and 

 like them, according to Latreille, many have the power 

 of leaping. They resemble the ichneumons in being pa- 

 rasitical in their larva state, and the ants by some genera 

 being without wings. The fifth is the most isolated group 

 of the whole ; yet the Tenthredines, or saw flies, are so 

 obviously allied to some of the typical Hymenoptera, that 

 they cannot possibly be removed from this order, merely 

 because their preparatory state or metamorphosis is differ- 

 ent. The perfect insect is immediately known by the ab- 

 domen being sessile, or joined to the thorax throughout 

 its whole thickness ; it consequently has no separate 

 motion, like that possessed by all the other tribes of this 

 order. As it is not our purpose to enter into the in- 

 ternal arrangement of these groups, in reference to what 

 may be the circular succession of their affinities, we 

 shall at once proceed to their analogies, as being the 

 chief basis upon which the foregoing arrangement of 

 the tribes is founded, 



