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proportion of their broods by tbeir attacks, but S. rugulosus was, of all 

 the species bred, the most copiously attacked. On removing a piece 

 of bark from a stick containing them, numerous larvse of the parasites 

 were visible, which had devoured the larvse of the beetles, before they 

 had entered their hybernacula in the wood, all those that had escaped 

 the parasites having done so. 



The parasites represented at least half the broods ; I bred from 

 them half a dozen species of Chalcididce, Cheiropachus quadrum being 

 much the most numerous. The greater liability of & rugulosus to 

 attacks from parasites has probably a close connection with the fact I 

 have already mentioned, that the entrances of its galleries of oviposition 

 are very obvious. 



Mr. Eye informs me he often finds Homalota coriaria in the wet 

 burrows of IS. destructor. 



Abergavenny, July, 1869. 



ON CENTROPTILUM, A NEW GENUS OF THE EPHEMERID^. 

 BY REV. A. E. EATON, B.A. 



A careful comparison of the mouth organs of the nymphs of nearly 

 all the British genera of JEpJiemeridce leads me to modify the plan of 

 classification which I drew up last year, in one or two important parti- 

 culars. The arrangement then proposed by me was based principally 

 upon structures of the imago, which seem to serve as a test (not alto- 

 gether satisfactory) of their affinities to each other. 



The most considerable changes that will have to be made are the 

 promotion of Ccenis and Tricorythus to the Leptophlebia group, to which 

 they seem to be closely united by means of the S. American Potaman- 

 thus inanis of Kollar's M.S., Pictet, 1843-5; and the reduction of 

 Siphlonurus to the Gloeon group. Whether Oligoneuria and Lachlania 

 should accompany Ccenis or not, is a point I am unable to decide upon 

 without an examination of their preparatory states ; and these are at 

 present unknown. The family seems separable into three principal 

 groups of genera : — (1) those with fossorial nymphs, with the mandible 

 produced externally into a porrect spine ; (2) those with nymphs which 

 crawl about the river-bed, whose females, when adult, have a ventral 

 lamina slightly produced out of the apex of the penultimate abdominal 

 segment ; (3) those whose nymphs can run nimbly about the water- 

 plants and river-bed, and swim rapidly. 



The separation of Centroptilum from Baetis is a mere alteration in 

 the detail of my former plan, and does not affect the general arrange- 

 ment. 



