INTRODUCTION. 



The three Families of which this, the Seventh Volume of the Coleoptera, treats — the 

 Erotylidae, the Endomychidse, and the Coccinellidae — form a not unnatural assemblage 

 of genera, though at first sight, and indeed on closer examination, they present con- 

 siderable divergence in points which have been usually regarded as of great importance 

 in Classification. Such is the tarsal structure, which in the first of these families is 

 pentamerous, but very much modified, becoming in the less specialized genera 

 tetramerous. In the second family — the Endomychidae — the foot is tetramerous, but 

 again modified; it is the basal joint which becomes obsolete, the fourth joint of 

 the tarsi being, as in the Erotylidae, a mere node at the base of the fifth or claw-joint. 

 In the Coccinellidae this nodal joint disappears. 



Notwithstanding this very important difference, which is without doubt correlated 

 with the habits of these insects, there are too many points of agreement to be passed 

 over. One of these is the presence of certain impressed lines on the metasternum and 

 on the basal abdominal segment, which are clearly in the higher groups, as the 

 Languriides and the Erotylides, the rudiments of original fossettes or broad depressions 

 for enabling the femora to lie closely retracted, with the tarsi and tibiae shut up like a 

 pocket-knife. These fossettes are retained and developed in the great majority of the 

 Coccinellida?, or become rudimentary in the Languriides and Erotylides, which have 

 the legs less retractile, and are quite lost in the Endomychidae and some genera of the 

 other two groups. 



The sole of the foot, like that of the Phytophagous section of Coleoptera, is broad 

 and spongiose in the great majority of genera, two joints (Coccinellidae), or three 

 (Erotylidae), being bilobed, flattened beneath, and furnished with papillae, which are 

 adapted for obtaining a firm hold on plants ; this character, through the phytophagous 

 Coccinellidae, affords a clue to the phylogenetic connection of these families with the 

 true Phytophaga. The Aphid-devouring instinct of the more highly developed 

 Coccinellidae would easily be explained on the view that certain phytophagous beetles 

 obtained and preferred this food while pursuing their original habit of life, and 

 possibly when the Aphides or Coccidae were so abundant that they could not be avoided. 



