io6 



MOLLUSCA, INSECTS, ETC. 



Fig. 54- 



else be present. They frequently cast their skins, 

 which may be mounted as microscopical objects, 

 showing the spiracles, or breath- 

 ing mouths, peculiarly adapted 

 to water. So fierce are these 

 common objects that they will 

 readily seize and hold on to 

 a stick with whose end they 

 have been taunted. The Dyticus 

 marginalis varies so consider- 

 ably in the appearance of the 

 sexes that they are not unfre- 

 quently mistaken for two dif- 

 ferent species of beetles. Their 

 Water Scorpion attacked by hind-legs are peculiarly adapted 



Larva of Dyticus. 



for swimming, owing to their 



Fig. 55- 



Fig. 56. 



Male of Dyticus marginalis. 



Female of Dyticus marginalis. 



being flattened out into oar-like expansions. The 

 fully-developed insect bears out the character it ob- 



