LARVAL FORMS OF COLEOPTERA 



Seveiitli and eighth abdominal segments with swimming hairs ; 

 ]i<ruhi i)resent 4 



4. AVith a i)air of long lateral gills on the six anterior abdominal 



segments Coptotominae {Coptotomus) 



No gills Thermonectinae (Acilius, Ther- 



monectes, Graphoderes, and 

 Eretes) 



5. Head anteriorly without dentation ; lignla either absent, or low 



and bilobed; nrogomplii present 



Dytiscinae (H i/daticus and 

 Dytiscus) (pi. 6 A, F, H) 

 Head anteriorly dentate ; ligula long ; urogomphi absent. 



Cyhisfrinae 



C. GYRINOIDEA 



Key to Families and Subfamilies 



1. Head subcirciilar with collnm narrow and distinct; mandible 

 falcate Avithont retinaculum 



Gyrinidae-Enhydrini (Dineu- 

 tes) (pi. 6 E, I-M) 

 Head elongate with collum about as wide as rest of head and 



not distinct; mandible with retinaculum 2 



2. Nasale without teeth Gyrinidae-Orecfochilhii {Orec- 



tochilus) 

 Nasale with two to four teeth in a transverse row. 



Gyrinidae-Gyrinmi (Gyrinus) 



D. PAUSSOIDEA 



The Paussoidea ajDproach the Caraboidea, especiallj' the Rhyso- 

 didae and the Carabidae, in fundamental characters but apparently 

 also the series Hydrophiloidea. In common with the first of the two 

 series, the Paussoidea possess a normal maxillarj' palpiger, four- 

 jointed antenna, and annular spiracles. In common with the second 

 of the series, they have a three-jointed maxillary palpus and a 

 single-jointed galea, characters, however, which also occur in the 

 isolated caraboid family Haliplidae. The posterior part of the ab- 

 domen is unique as are also the legs which are onlj^ three-jointed 

 and are curved upward. However, reduced legs but of a different 

 type are found both in the Caraboidea, for instance, in stages of 

 Lehia scapularis, and in the Hydrophiloidea, for instance, in 

 Sphaeridmm. It is for practical reasons mostly that the series 

 Paussoidea has been established and placed at the end of the 



24 



