18 



BULLETIN 689, U. S. DEPARTMENT OF AGRICULTURE. 



PERIOD OF INCUBATION OF EGGS. 



Table III gives data on eggs that were laid by females in the 

 insectary, in which place the eggs were also kept until they hatched. 

 Jars containing the adults and eggs were examined each morning 

 and the date on which eggs were noted is taken to be the date on 

 which they were deposited. In a like manner the date when nymphs 

 were found is taken as the date of hatching. 



The eggs composing any one cluster usually hatched at approxi- 

 mately the same time. An exception to this occurred in the case of 

 a cluster of eggs deposited on October 16. Nymphs issued from some 

 of these on October 29, when the thermograph reached a maximum 

 of 87° F. at noon. At 2 p. m. 1 a "norther" caused a sudden drop in 

 temperature, the thermograph registering 34° F. the next morning. 

 No more nymphs were observed to issue on October 30 or 31 when 

 the maximum temperatures were 53° and 63° F., respectively, but 

 on November 1, when the maximum temperature was 70° F., other 

 eggs hatched. 



The temperatures to which the different egg clusters were exposed 

 apparently governed to some extent the period of incubation, the 

 period being longer for the lower temperatures. 



Table III — Incubation periods of egg clusters of Nezara viridula. 1 



De- 

 posited. 



Hatched. 



Days. 



De- 

 posited. 



Hatched. 



Days. 



De- 

 posited. 



Hatched. 



Days. 



July 22 



July 28 



6 



Aug. 18 



Aug. 23 



5 



Sept. 4 



Sept. 9 



5 



July 22 



July 28 



6 



Aug. 20 



Aug. 26 



6 



Sept. 5 



Sept. 10 



5 



July 30 



Aug. 4 



5 



Aug. 20 



Aug. 26 



6 



Sept. 6 



Sept. 12 



6 



Aug. 9 



Aug. 14 



5 



Aug. 22 



Aug. 28 



6 



Sept. 6 



Sept. 12 



6 



Aug. 13 



Aug. 18 



5 



Aug. 22 



Aug. 28 



6 



Sept. 6 



Sept. 11 



5 



Aug. 13 



Aug. 18 



5 



Aug. 24 



Aug. 30 



6 



Sept. 18 



Sept. 25 



/ 



Aug. 14 



Aug. 19 



5 



Aug. 25 



Aug. 31 



6 



Sept. 27 



Oct. 6 



9 



Aug. 14 



Aug. 19 



5 



Aug. 26 



Aug. 31 



5 



Oct. 16 



Oct. 29 



13 



Aug. 15 



Aug. 20 



5 



Sept. 2 



Sept. 7 







Oct. 18 



Nov. 9 



22 



1 For temperatures to which eggs were exposed see figure 13. 

 HABITS OF THE NYMPHS. 



The nymph issues from the egg through a circular opening at the 

 top which it makes by removing the cap or lid. The brownish 

 T-shaped egg-burster, by means of which the cap is removed, is 

 usually left in the eggshell when the nymph emerges. 



During the first instar the nymphs ordinarily cluster together, 

 often on the eggshells, and apparently do no feeding. After the 

 first molt they begin to search for food and soon become scattered. 

 Subsequent to the first molt, and especially during the later instars, 

 the nymphs are active and when disturbed they often seek protection 

 by moving to places out of the disturber's range of vision. They are 

 found usually upon those portions of the plant on which they prefer 

 to feed — -the growing shoots and more especially the developing fruit. 



All references to "clock time" refer to Standard Time. 



