158 THE UNIVERSITY SCIENCE BULLETIN. 



lacks the siphon. De Geer said that the young come forth in the middle 

 of the summer, the complete development taking two months. 



Number' of Instars. We are indebted to Roesel, 1855, for figures of all 

 five nymphal instars of the European bug. 



Food Habits. This bug does not pursue its prey to any great extent; 

 but lies in wait for it. Its flat body enables it to float with more sta- 

 bility on the surface film than its relative Ranatra. The photograph on 

 plate V shows the result of placing two bugs in a deep aquarium with- 

 out any trash for support. When the two bugs encountered each other 

 at the surface the smaller Nepa won the fight. Wood, 1884, says its 

 food is mostly the larvae of May flies and whirligig beetles. Kirkaldy, 

 1906, says they are seemingly content with Daphnia and Cyclops, but 

 suck fish eggs, and even attack small fish and tadpoles. 



Behavior. Severin & Severin have studied the behavior of these in- 

 sects somewhat, together with Ranatra. Nepa has interested biologists 

 from an early date, for MouflFet, 1634, figured it. Frisch, 1728, also 

 figured it. See plate IV. 



Description of Stages. The egg has been figured and described from 

 Roesel's time to Brocher's. The nymph described by Roesel, 1746-'61 ; 

 Burmeister, 1835; and Kirkaldy, 1911. Walter Dogs, 1908, gives some 

 structural details in his "Metamorphose der Respirations organe Bei 

 Nepa cinerea." 



The Egg. 



Brocher describes the egg of the European form as follows: 



Size. "2.5 mm. long. 



Color. "Whitish yellow. Rosette of filaments at the tip, number of 

 these varies from 7 to 9." 



The writer has found as many as 11 well-developed ova in one female 

 N. apiculata in July. On plate XVIII is a figure of one of these. The 

 description follows : 



Egg of Nepa apiculata. 



Size. Length, 2.8 mm.; width, 1.35 mm.; length of filaments, .96 mm. 

 to 1.05 mm.; diameter of the crown, .42 mm. 



Shape. An elongate oval, irregular in outline; somewhat pointed at 

 one end. The other end bearing on one of its slopes a crown of eleven 

 slender filaments arranged in a circle. See the figure on plate XVIII. 



On one side near the pointed end and diagonally across from the 

 center of the filamentous crown is a circular raised area. 



Color. Pale yellow; filaments whitish; the raised circular area dark. 



Genus RANATRA Fabr. 



We have here many more biological notes than for Nepa. Bueno 

 has given us a fairly complete account of Ranatra quadridentata. In 

 fact more has been written about the biology of this group of water bugs 

 than any of the others. Aldrovandus, 1602, under the name of Tijncla 

 aquatica mentions it. Swammerdam calls it Scorpius aquaticus. 



Habitat. Found in the tangles of trash and vegetation in the water. 

 Kirkaldy and Lucas both record that Ranatra is at home in the mud at 



