APHIDES. 249 
the aphidivorous character of the coleopterous 'elephoride 
(Entom. xi. 163, 255). In one of the late Mr. IF. Walker’s 
numerous notes on Aphides we read, “'The comfrey Aphis is the 
frequent prey of a little red dipterous larva, which seldom attacks 
other species.” (Entom. vi. 27); this was doubtless the larva of 
the little gall-gnat, Diplosis aphidimyza, Rondani. Dr. F. Low 
found it preying on the Aphides inhabiting seven different plants, 
so it by no means confines its attacks to one species. We now 
come to the Hymenoptera; their influence on Aphis increase is 
particularly powerful. Various fossorial Crabronidé store up 
insects of different orders in their cells as food for their future 
progeny, these being paralyzed and not killed by the stings of the 
parent bees; species of the genera Crabro, Stigmus, Diodontus, 
Passalecus, Pemphredon, Cemonus, and Psen are known to 
provision their cells with plant-lice, and there are probably 
others. Marshall’s ‘Catalogue of the British Oxyura’ includes 
8783 species distributed amongst 83 genera; but of their economy 
we know next to nothing. It is not improbable that many are. 
aphidivorous. 
Of the limiters from within—the true parasites—all are 
hymenopterous, and comprise species of the Cynipide, the 
Ichneumonidae, and the Chalcidide. The numerous species of 
the genus Allotria (Cynipide) complete their metamorphoses 
within the bodies of the various Aphides; they stand at the head 
of all the internal parasites, being very closely related to the true 
gall-flies. The species comprising the genera Toaares (T'rionyz), 
Ephedrus, Monoctonus, Praon, Aphidius, Lysiphlebus, Dieretus, 
and T'rioxys, forming the Braconid group Aphidides of the 
Ichneumonidae, are all parasites in the bodies of various plant-lice; 
some of the species, more especially of Aphidius, are at times 
particularly abundant, as instanced by the numerous pierced 
inflated Aphis-skins, which are such obvious evidence of previous 
parasite occupancy. Coming to the Chalcidide, the enumeration 
of the Aphis-frequenting genera would be wearisome; suffice it to 
say they are numerous, though as yet but little understood. The 
economy of insects is truly wonderful; here we have the plant 
limited by an Aphis, this is preyed upon by an Aphidius, which 
in turn serves to nourish an Asaphes, a Chrysolampus, or not 
improbably one of the Ceraphronide (Oxyura). ‘These, of course, 
are the cultivators’ enemies, being parasitic in a degree too far 
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