A laboratory experiment was conducted to estimate the developmental
threshold for immature stages of the spiny bollworm. Earias insulana (8oisd.) and the
accumulated thermal units needed for completion of one generation. Eggs from
different Agro-ecosystems viz. Qalyubyia. Sharkia and Minia Governorates were
subjected to the present experiment in addition to a laboratory strain.
Obtained results .reveat that egg developmental period was greatly affected
by rearing temperature. At 20'C. eggs from Qalyubyia strain developed faster as
compared to other field strains. At 30'C. eggs of the laboratory am: field strains
developed at a range of 2.8-3.0 days. The lower thresholds of egg we:» 7.55. 7.59
and 10.5rC for Sharkia. Qalyubyia and Minia, respectively, while thermal units
needed for eggs to hatch were 64.69.60.61 and 54.05 DDs.
Larvae of the laboratory strain were faster in development than others of
different Agro-ecosystems. At 25°C. larval duration lasted for 14 5±1.15 days for the
laboratory strain while it ranged between 16-18 days for the field strains. The
developmental threshold did not significantly differ between the tested governorates
since it ranged between 11.02°C and 12.39'C. Thermal constants, however were
higher for Minia strain (277.7800s) followed by Sharkia (243.90 ODs). Qalyubyia
(238 09 cos: and laboratory strain (227 27 DDs).
Pupae of the laboratory strain developed faster than those reared from
different Agro-ecosystems. At 25 and 30'C, pupae from Sharkia and Qalyubyia eco-
types developed faster than those of Minia Governorate. The zero of development
values were very close, it ranged between 10.26 and 11.06'C. Thermal requirements
were 181.82 DDs for Minia and laboratory strains, 168.08 DDs for Qalyubyia and
222.22 for Sharkia strain.
Since females resulted from eggs collected from different Agro-ecosystems
and fed as larvae on an artificial diet failed to lay eggs after mating, so the pre-
oviposition period was estimated for females resulted from laboratory strain only. This
period ranged between 4.33±0.SO and 2,30±0.48 days at 20DC and 30'C,
respectively. The zero of development for this pence was 9.1 T'C and the thermal
requirements estrrDC respectively. The zero of development for the wholegeneration was estimated as 11.04°C, while the amount of thermal units needed forcompleting one generation were 512.82 ODs.