1 AQUATIC BEETLES 41 



pith, and then lays a single egg in the cleft. The 

 ovipositor, which projects from the hinder end of the 

 body, is armed with two small, hard, pointed plates, 

 which enclose the oviduct, and it is with these that 

 the incision is made.^ March or April is usually the 

 time. From eggs so laid minute larvae proceed, hatch- 

 ing out in about three weeks. They grow very fast 



Fig. 3. — A. Female Dytiscus, laying eggs. B. The ovipositor, protruded. C. Eggs 

 of Notonecta, attached to stem of rush. D. Egg of Dytiscus, laid in excavation 

 in rush. From Riigimbart. 



when well supplied with food, and attain their full 

 larval development in four or five weeks, changing 



^ Regimbart, Ann. Soc. Enf. France, 1875. The eggs are 

 very elongate. Dr. Sharp informs me that they are often 

 accompanied by a wliite maggot, exactly like them, but rather 

 shorter. In Yorkshire the eggs are more commonly laid in the 

 midribs of Pond-weed (Potamogeton natans). 



