§ IviSec^S 



PREFACE. 



The Gyrinidse are generally considered as a family of the sub-order 

 Adephaga. , They are indeed adephagid in some general .characters, in 

 other characters, however, they are abnormal and approach other families, 

 which are far from the adephagous series. From this I concluded 1 , 

 concerning their phylogenetic origin, that the Gyrinidse must be older 

 than the true Adephaga, which opinion was already expressed by La- 

 meere 2 , Fowler 3 and other authors. For this reason, it would perhaps 

 be best, to consider the Gyrinidse as an isolated family, like for example 

 the Palpicomia, with which they have probably some, though very 

 distant, relations. Nevertheless, the nearest allies existing are the Ade- 

 phaga, but if placed in this series, this requires a subdivision, and I 

 feel inclined to follow the arrangement of Leng 4 and of Tillyard 5 , who 

 unite the true Adephaga in a superfamily (Caraboidea) and consider the 

 Gyrinoidea as a section of equivalent value. I cannot agree with Hatch 8 , 

 who regards the Gysinidea as simply derived from the Dytiscidee, and 

 must therefore reject the arrangement of Handlirsch 7 , who unites the 

 Gyrinidse with the aquatic families of the Adephaga in his Hydrocan- 

 tharini. 



The Gyrinidse are beetles of small to medium size, which are usually 

 found in groups on the surface of the water, on which they can swim 

 with great rapidity and perform complicated whirling evolutions. They 

 are fairly adapted to this manner of life by the general shape of their 

 body and the peculiar structure of "the antenna and the natatorial 

 legs, the latter being modified so as to form short swimming- paddles. 



The beetles are found on standing as well as on running waier, and 

 some groups, especially Orectochilus and Porrorhynchus seem to prefer 

 rivers and streams of swift current. Apparently the beetles — at least 

 the Orectochili — do not like the bright sunshine, as they are found 

 generally in deeply shaded places and iu one case even in the interior 

 of a cave, and it may be remembered, that the palcearctic representa- 

 tive of Orectochilus is nocturnal. 



1 Och?. Ent. Zeitschr. FrcrnkJ. XXXX 122 (1026). 



"Lanieere. Ann. S. E. Belg. XLIV 37'5 (1900). 



3 Fowler. F n. Brit. liul. Col. 50 (1912). 



•Leng. Cal. Col. N. America 2G (1920). 



6 Tillyard, Ins. of Austral, and N. Zeal. 187 (1926). 



s Hatch. Pap. Mich. Acad. V. 430 (1925). 



' Handlirsch. In Schroder's Hand'}, d. EM. Ill 550 (1925). 



