BIONOMICS OF CERTAIN HYMENOPTERA PARASITICA. 405 



may often be observed to have been pierced by a round hole. Those dead 

 Aphidse which have no round hole in them, when collected and kept in 

 stoppered phials, will be found sooner or later to give rise to small Hymeno- 

 pterous insects, generally jet-black. In text-figs. 6-11 are drawn four of 

 these minute insects ; study of these forms shows that the parasitic species 

 are mostly Braconidse belonging to the genus Apiiidius (text-fig. 10). The 

 flies belonging to this genus always seem to emerge from the dry carcase of 

 the Aphid by means of a neat round hole and a distinct lid (text- fig. 11). 

 Now there are other small black flies which emerge from these Aphid 

 carcases, and which are not Braconidse (Aphidius). These, in the cases 

 examined by me, almost always seem to be hyperparasites on the Aphidius 

 (text-figs. 6 & 8). All the flies which emerge from the Aphids, and which 

 are not Braconidse, are either Chalcids, Cynipids, or Proctotrypids, and 

 these leave the dry carcase of the Aphid by making a rough hole without a 

 lid (text-fig. 9). This may be compared with the peculiar case already 

 mentioned in connection with Microgaster and Mesochorus, PI. 24. fi<j-. 1 & 

 PL 25. fig. 9, where the same thing also happens with regard to parasite and 

 hyperparasite. 



The Ichneumonidse are another family of parasitic Hymenoptera which 

 attack caterpillars and other larger insects. From an examination of the 

 literature, and from the persojial experience of observers in the Hope Depart- 

 ment, Oxford, and of myself, I do not think any Ichneumons prick Aphids. 

 Aphid hymenopterous parasites are all from the Braconidje, Chalcididse, 

 Proctotrypidse, or Cynipidce. It seems certain that the majority of, if not all, 

 Chalcididse associated with Aphidse are hyperparasites, while the Gynipidse, 

 represented by forms like Allotria flavicornis, are possibly all hyperparasites 

 also. The Aphidiidse (Braconidse) are all parasites as far as I know ; the 

 case of the' Proctotrypidse is still doubtful. Mr. Britten, of the Hope Depart- 

 menl, considers that these forms are parasites and not hyperparasites. 



Explanation of Text-Jigs. 6-11 (page 404). 



Hymenopterous parasites and hyperparasites associated with Aphidse (Plant Lice). 

 In text-fig. 10 is the typical parasite, a Bracon, Aphidius avence (Hal.). All the other 

 hymenoptera in these figures are possibly hyperparasites on the Aphidiidse (Braconidge). 

 In text-fig. 6 IS, Allotria flavicornis (Htg.), which is neither Bracon, Chalcid, nor Ichneumon, 



but belongs to the Cynipidse or Gall-flies. 

 In text-fig. 7 a Proctotrypid, Ceraphron carpenteri <S (Curt.) is drawn. Whether a 



parasite or a hyperparasite is not known. 

 In text-fig. 8 is a Chalcid hyperparasite (on an Aphidius), Asaphes vulgaris (Nees). 



The Aphidiidse emerge from the dry aphid-skin by means of a round, cleanly cut hole 

 -with a lid on one side, as in text-fig. 11. All the other insects drawn in these text-figures, 

 Chalcids, Cynipids, and Proctotrypids, emerge from the dry aphid-skin by a rough hole, as 

 in text-fig. 9. (Compare PI. 24. fig. 1 and PI. 25. fig. 9.) 



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