ADEPHAGA. 



49 



Sub-Order I. ADEPHAGA. 



The Adephaga have by most authors been placed at the head 

 of the Coleoptera by reason, in great measure, of their predatory 

 habits, as answering to the beasts of prey and the rapacious birds. 

 By recent writers, however, they are placed at the lower end of 

 the order, as the most primitive series, the reasons alleged being 

 the visibility of the second ventral segment of the abdomen*, 

 the simple antennae, the tubular testes, the more complicated 

 structure of the wings, and the campodeiform larvae. Several of 

 these characters are found in other groups, but in the Adephaga 

 there is a combination of a large number of characters which are 

 believed to point to a primitive origin. At the same time we know 

 very little for certain with regard to the significance of these 

 characters from a phylogenetic point of view, and what we do know 

 is perpetually being modified and corrected by fresh discoveries. 

 As a matter of fact comparatively few species (indeed an in- 

 finitesimally small number, compared with the probable total) have 

 been examined in each group and generalisations may be easily 

 upset. 



The chief characteristics of the Adephaga have been mentioned 

 above: the venation of the wings is very distinct and important, 

 the areola oblonga, formed by the two cross veins joining the 

 median veins, being very characteristic. In the Cicindelid^ it 

 is usually wanting, although it is found in Pogonostoma, but 

 there are other good characters which may distinguish the 

 venation. 



The number of the Malpighiau tubes is four (these are usually 

 four or six), and this would appear to be the primitive number ; 

 some authors, however, believe that six is the primitive number 

 and derive the four from the six. Lameere, if consistent with his 

 general argument, should uphold the latter, as in his classification 

 he almost invariably derives the less from the more. In Cyphon 

 (including Helodes) considerable difficulty appears to have been 

 caused by the fact that there are four Malpighian tubes in the 

 larvae and six in the imago, but if four is the primitive number the 

 difficulty vanishes. Many more beetles will probably be found 

 to show the same arrangement in their larval and perfect states. 

 The filiform antennae (very rarely irregular or moniliform) and 

 the active campodeiform larvae are also characteristic of the 

 Adephaga. 



The families which have been usually assigned to the group are 

 the Cicwdelid^:, CakabidjE, HALiPLiDiE, Dytiscidte, Hygeobiidji 



* In the great majority of Coleoptera, the first visible ventral plate is the 

 lower sclerite of the third abdominal segment. 



E 



