968 On Aquatic Carnivorous Coleoptera or Dytiscidce. 



between the two internal laminte of the hind coxae ; 8, the ciUatiun of the posterior 

 tibia3 and tarsi ; and 9, the change of form in the hind legs by which they are 

 adapted for swimming. Of these characters, No. 1 is quite as marked in many 

 Pseudomorphini of the Carabidee and in Cyclosomus as it is in many Dytiscidoe 

 and more so than in a few Dytiscidse. No. 2, the structure of the Dytiscid head 

 is greatly approximated by the Pseudomorphini. 3, the antennte in several 

 members of the Pseudomorphini, Scaritini, and Trachypachini are more or less 

 completely deprived of sensitive pubescence ; in other cases (as in Anthia) the 

 exserted setae are but little developed. 4, a prosternal process always exists in 

 the Dytiscidse, but is also found in some CarabidiB, especially Cyclosomus, 

 Trachypachini and Omophron. 5, the prosternal process in the Dytiscidse does 

 not always reach the metasternum, it fails to do so in the Vatellini, in Tyndalhy- 

 drus, and in Andex ; while on the other hand in Cyclosomus of the CarabidtR, the 

 prosternal process reaches the metasternum. 6, the external lamina of the hind 

 00X88 is always much larger in the Dytiscidse than it is in the Carabidje, it varies, 

 however, extremely in size in the former family, so that from this character alone it 

 would not be easy to say where the line of demarcation between the two families 

 should be drawn. 7, this, like the preceding character, is constant in the Dytiscidfe, 

 but the hind coxse are likewise co-adapted in some Carabidse (Trachypachini and 

 other members of the first series of Carabida'^), so that here again the Dytiscid 

 character is only an exaggeration of what it is in some Carabidaa. 8, the hind 

 tibiae and tarsi are in some Dytiscidse but feebly ciliated, and in some members of 

 the Scaritini group of Carabidse the hind tibias are strongly ciliate externally. 9, 

 in some of the Dytiscidse there is so little difference from the Carabidse in the 

 form of the swimming leg, that the character cannot be relied on as diagnostic of 

 the family. 



We see then that the relations between the two families are very intimate, so 

 intimate that it may be, I believe, stated with correctness, that the Dytiscidse are 

 modified Carabidse. By which I mean to say that there is reason to believe that 

 the remote ancestors of the Dytiscidse, had before they inhabited the waters 

 acquired to a considerable extent an organization similar in many respects to that 

 which some Carabidse still possess. In the genus Pelobius we have clearly an 

 altered Carabid ; and the frequent persistence in other Dytiscidse of traces of 

 a Carabid-like structure of the hind tarsus, and other similar facts makes one 

 believe that what is clearly true of Pelobius, is probably true of other Dytiscidse. 



Herr Kolbe in the Deutsche Entomologische Zeitschrift, 1880, pj). 258, ct seq., 

 has published a new, and from many points, very interesting classification of the 

 Carabidse, Dytiscidse, Cicindelidse, Haliplidte and Gyrinidse, based on the theory 

 that the land beetles are descendants of the water beetles. This is, however, 

 most certainly an erroneous conclusion ; it is, as I have said above, possible to 

 believe that the Dytiscidse are modified Carabidse, but it is quite incredible to me 



