MODE OF OVIPOSITION 



519 



tail, and further observations are much needed. In the cockroach 

 (Thyllodromia), Wheeler has seen the eggs pass out of the oviduct 

 and become arranged in the ootheca, in a way similar to that in 

 the account published by Kadyi on Periplaneta. 



" When about to form the capsule, the female Blatta closes the genital arma- 

 ture, and the two folds of the white membrane which lines the oothecal cavity 

 close vertically in the middle line. Then some of the contents of the colleterial 

 glands are poured into the chamber, and bathe the inner surface of the posterior 

 wall. The first egg glides down the vagina from the left ovary, describes an 

 arc, still keeping its germarium-pole uppermost, after having pressed the 

 micropylar area against the mouth of the spermatheca, passes to the right 

 side of the back of the chamber, and is placed perpendicularly two-thirds to 

 the right of the longitudinal axis of the insect's body. The next egg comes 

 from the right ovary, describes an arc to the opposite side of the body, decussat- 

 ing with the path of the first egg, and is placed completely on the left side of the 

 median line. The third 

 egg comes from the left 

 ovary, and is made to 

 lie completely on the 

 right side of the median 

 line ; and so the process 

 continues, the ovaries 

 discharging the eggs 

 alternately, and each 

 egg describing an arc to 

 the opposite side of the 

 capsule. The oothecal 

 chamber soon becomes 

 too small to contain all 

 the constantly accumu- 

 lating eggs, so the anal 

 armature opens and al- 

 lows the end of the cap- 

 sule to project. A raised 

 line, the impression of 

 the edges of the white 

 membrane, runs down 

 the end of the capsule. 

 The last egg deposited 

 comes from the right 

 ovary, and lies two-thirds 

 on the left, and one- 



third to the right, of the 



, . , . A 



median line. As soon 



as the eg" 1 is laid a 



turther discharge from 



the colleterial glands spreads over the vaginal or anterior wall of the cavity, 



and becomes evenly continuous with the secretion which has before been 



spread over the back and the sides of the capsule by the white membrane. 



"The crista, a cord-like ridge running the full length of the dorsal surface of 

 the capsule, is a thick-walled tube, either half of which is formed by the edge 

 of the side walls of the capsule split into two laminae. The rhythmical clasping 



-p m 492. Rocky Mountain locust (aa) depositing its eggsir); 

 *> the earth partially removed, showing (e) an egg-mass already in 

 place, and (d) one being placed ; / shows where such a mass has 

 been covered over. A, oviposition ; .7, position of oviduct ; g, egg- 

 u 'de ; , egg- -5, egg-mass of the same ; a, from side, b, from 

 beneath, c, from above. After Riley. 



