10 



CIRCULAR 3 



IT. S. DEPARTMENT OF AGRICULTURE 



SEASONAL HISTORY 



The length of each stage depends largely upon climatic condi- 

 tions, development being more rapid in warm weather. Insect ary 

 breeding experiments and field observations have shown that in 

 summer the following average periods are required to complete 

 each stage of the female : 



Days 



First instar 10-11 



Second instar 15-17 



Preoviposition period 17-20 



First egg to emergence of crawlers__ &-11 



Total period 51-59 



Figure 5. — Ventral view of producing female scales in coverings. These have been 

 lifted from the twigs to show the underside of the females, with the characteristic 

 white patches. Enlarged 9 times. 



The majority of the scales pass the winter in the adult stage, but 

 there is no well-defined hibernation period. The number of eggs be- 

 neath the coverings begins to increase in January, and emergence of 



young may com- 

 mence in February 

 or March, depending 

 on the temperature. 

 In the New Or- 

 leans district there 

 are usually three 

 complete generations 

 each year, but in 

 years when the tem- 

 peratures are higher 

 than normal a partial 

 fourth generation 

 may develop. In 

 1926, 1927, and 1928, 

 respectively, the 

 dates of first appear- 

 ance of crawlers of 

 each brood were as follows : First brood, March 30, February 21, and 

 March 19; second brood, June 22, May 26, and June 20; third brood, 

 August 17, July 23, and August 16. 



Because the developmental rates are largely dependent on tem- 

 perature, it is possible to predict accurately the time of appearance 



Figure 6. — The adult male amphor scale, 

 enlarged. 



Greatly 



