4 



CIRCULAR 8 6 9. U. S. DEPARTMENT OF AGRICULTURE 



Seasonal Occurrence 



The seasonal occurrence of the cigarette beetle varies with the con- 

 ditions under which tobacco is stored and manufactured. In heated 

 buildings, or in the subtropical climate of Florida, there may be no 

 well-defined hibernation period but a slowing of development during 

 the winter. Under such conditions all stages of the insect may be 

 found at almost any time of year. In North Carolina and Tennessee 

 and farther north the beetle 'passes the winter in the larval stage in 

 tobacco or other hosts. There is usually heavy mortality of immature 

 larvae, and in severe winters the population of mature larvae may be 

 materially reduced. If the tobacco temperature remains below 36° F. 

 for 16 consecutive days, all larvae are killed, and such low tempera- 

 tures occur outdoors frequently in Virginia. In brick warehouses 

 and factories, however, infestations always survive. 



In the Richmond. Va. area the larvae begin to pupate late in the 

 spring, and the first adults of the spring brood usually emerge late in 

 May. Near Charleston. S. C, or Wilmington. N. C. emergence may 

 start as early as the last week of March. The generations overlap, but 

 peaks of emergence of the different broods are rather sharply defined. 

 At Richmond the spring peak is reached usually about the middle of 

 June. Since the major portion of a generation completes develop- 

 ment in 50 to 60 days, there are ordinarily two generations and a 

 partial third generation in North Carolina and Virginia. This 

 seasonal occurrence is shown in figure 2. At Richmond there is usually 

 a peak emergence in June, another in August, and a third in October. 

 The third generation is usually smaller than the others, but in mild 

 weather it may be large. A large number of second-generation larvae 

 and all the third-generation larvae pass the winter in this stage. 





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 MAR | APR MAY JUNE JULY | AUG | SEPT 1 OCT NOV 1 DEC 



figure 



2. — Seasonal occurrence of the cigarette beetle in Virginia and North 



Carolina. 



The population of cigarette beetles fluctuates widely, but there is 

 some indication of cycles of abundance. Beetles appear to be more 

 abundant every other year and perhaps there is a longer cycle, but 

 the picture is somewhat obscured. In any storage warehouse the most 

 important factors influencing population are temperature, relative 

 humidity, and types, grades, age. and quantity of tobacco present. 

 At times parasitism may also be of some importance. 



