Abstract
A research on the life cycle of Glena bisulca Rindge on cypress, Cupressus lusitanica Miller, was conducted in an insectary exposed to field conditions in a commercial plantation of conifers at 16,3°C of average temperature. The result of these studies were compared with previous ones at 22,4° C and 21,1° C con cypress and Pinus patula Schl. et Cham. respectively.
In the field at 16,3°C G. bisulca undergoes five or six larval instars, however, there is a higher incidence (60 0/0) of individuals reaching the sixth instar. Females have a higher tendency to reach the sixth instar and males to reach the fifth instar.
There were not big differences between the two groups in duration of life cycle. The larval period varied between 54,2 to 56,4 days, prepupa from 3,7 to 4,5 days and pupa took 39,5 to 41,6 days. The life cycle from egg hatching to moth emergence was around 100 days.
Temperature had a definitive effect on the length of G. bisulca's life cycle. Under field conditions at 16,3°C it was about 40 days longer than the life cycle reported by Drooz and Bustillo (1972) at 22,4° C on cypress and about 32 days longer than the one studied by Alomia (1974) at 21,1° C on P. patula.
In this study there was a greater frecuency of insects reaching six instars. In the five-instar group there were more males than females and the reverse ocurred in the six-instar group. This fact indicates that in the field, females have a higher tendency to undergo six instars and males to undergo five instars.
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