classification of the Adephaga. 67 



look, I think, upon Dr. Horn's families as natural ones. 

 The distinction between the Cicindelidce and Carabidce 

 long jiuzzled entomologists, and a few years ago the 

 opinion of naturalists seemed to tend to uniting them as 

 only one family, but the remarkable structure of the 

 parts of the buccal cavity in the Cicindelidce always left 

 doubts as to the propriety of this course; and since Dr. 

 Leconte pointed out that in addition to the mouth- 

 differences there existed an important difference in the 

 structure of the head, the general feeling has been 

 to keep them as quite distinct aggregates. Dr. Leconte 

 defined the difference between the two families in terms 

 of the insertion of the antennae, and this is repeated by 

 Dr. Horn, who states that Cicindelidce have '* antennae 

 inserted on the front above the base of the mandibles," 

 while the Carabidce have " antennae arising at the side of 

 the head between the base of the mandibles and the 

 eyes " : this definition is not, however, a very good one, 

 for there are certain Carabidce which approximate much 

 in this respect to the Cicindelidce (cf. Loricera), and 

 some, at any rate such as Trichognathus, that this 

 definition would bring into the Cicindelidce. Fortunately, 

 however, it can be replaced by a formula that is, I 

 believe, quite exact, and even more easily appreciated, 

 viz., Cicindelidce, " clypeus extending laterally in front 

 of the insertion of the antennae"; Carabidce, "clypeus 

 not extending so far towards the sides as the insertion of 

 the antennae." 



As regards the separation of the Haliplini from the 

 Dytiscidce, and its treatment as a distinct aggregate, 

 there is, I think, no reason to doubt this being a natural 

 proceeding. So also as regards Pelobius ; I have already 

 expressed my opinion that it should not be left in 

 the Di/tiscidce ; and as it is not allied to any Carabid, 

 Dr. Horn is probably justified in isolating it. 



In discussing Amphizoa (Tr. Koy. Dub. Soc, n. s., 

 vol. ii., p. 844), I expressed the opinion that it might be 

 treated as an aberrant member of the Di/tiscidce, this 

 view being largely derived from the fact that the 

 Dtjtiscidce were the only Coleoptera known to possess a 

 structure of the middle coxal cavity similar to what 

 exists in Ampliizoa. This was, however, before Dr. Horn 

 had benefitted us by his important discovery that 

 Mormolyce — an undoubted member of the Carahidce — 

 likewise possesses this same structure. This introduces 



