104 THE UNIVERSITY SCIENCE BULLETIN 



remains perched upon her back as she busies herself with egg laying, 

 mating being attempted and often consummated between her labors. 



In starting the drill in a particularly stubborn or inconvenient place 

 the female not infrequently uses one of her hind legs to steady and stiffen 

 or support the drill. One female after making several attempts employed 

 her right hind leg in such a manner that the tarsus was turned at an 

 angle with the tibia and the angle thus formed used to direct and aid 

 the ovipositor. 



During the process of oviposition the female often defends herself 

 from molestation by kicking vigorously with the hind legs when disturbed. 



Incubation. The egg stage lasts seven to nine days. The deep red 

 eye spots are visible two days before hatching. 



Hatching. At hatching the young nymphs, still enclosed in their 

 embryonic membrane, work their way up through the little circular 

 openings of the stem. This is a remarkable feat, considering the size 

 of the nymph and the size of the hole, but is aided materially by the 

 peculiar backward pointed pegs on the thin embryonic membrane. When 

 well out of the stem, this membrane is cast and the nymph takes its 

 place upon the water. 



Number of Instars and Molting. There are five nymphal instars. 

 Molting takes place upon a support of floating material or even upon the 

 water itself. The ruptures of the integument take place along the same 

 lines as for Gerrids. 



Maturity and Fecundity. After passing through the five nymphal 

 instars, spending two or three days in each, mating occurs and oviposi- 

 tion begins about the third day. One female emerged August 1, began to 

 lay August 3, and died August 12, having laid 44 eggs, an average of 

 nearly five eggs per day. Some of the females in isolation laid an aver- 

 age of less than this, while one female under observation laid 18 eggs in 

 24 hours, a surprisingly large number, considering the size of the egg 

 and adult. 



DESCRIPTION OF STAGES. 



The Egg. 



Size. Length, 0.875 mm.; greatest diameter, 0.187 mm. to 0.250 mm.; 

 diameter of exposed circle, 0.15 mm. 



Shape. The egg is elongate-oval, with a curved neck terminating in 

 a flat surface which marks the exposed end of the egg as it lies in situ 

 in the stem of some plant. 



Color. When first laid, white; in the course of two or three days it 

 has become watery transparent, with portions of the embryo beginning 

 to take form. These eggs are buried singly. The exposed end of the 

 egg shows up as a shiny membranous circular spot on the surface of 

 the plant which bears it and is visible to the naked eye. This spot, 

 though clear white when first laid, presents at about the second day a 

 very faint ring of pink which darkens to a deep pink after 25 hours. In 

 the course of another day or two this gradually fades, and two days be- 

 fore hatching the deep red spots may be seen through clear stems. 



