On the Biology and Structure of the Larvae 

 of Hydrophilus caraboides L. 



By 

 E. N. Pavlovsky, M.D., D.Sc, 



Professor of Zoology at the Military Academy of ]\Iedicine, Petrograd. 



With Plate 27 and 16 Text-figures. 



In May 191S I captured in the vicinity of Petrograd some 

 cocoons of a hydrophilus beetle, one of which I kept for breeding 

 purposes. On June 13 there emerged about fifty small larvae 

 very similar to Hydrophilus caraboides. These latter 

 are characterized by the presence of a pair of lateral (pleural) 

 appendages covered with a dense brush of hairs on each of the 

 seven abdominal segments (Text-fig. 13, j9?a). 



In my larvae (Text-fig. 1) these pleural hairy appendages 

 were also present, but with the difference that each appendage 

 bore on its summit a long thin liair. This peculiarity caused 

 me to look for other differences between my larvae and the 

 description of the larvae of Hydrophilus caraboides, 

 as given by Schiodte in his paper, ' De metamorphosi eleuthera- 

 torum observationes ; bidrag til insekternes undviklingshistorie ', 

 1861. 



These differeiices may best be pointed out by a parallel com- 

 parison of the text of Schiodte's diagnosis and the description 

 of the newly emerged larvae as observed by me, as follows : 



Hydrophilus car a- Hydrophilus caraboides 



boides S c hi odte Caput — a larva at first stage. Head 

 obovatum. irregularly tetragonal, shaped 



rather like a trapezium turned 

 with its base forward, and with 

 broken sides. 



