author(s)
Saleh TA, Ahmed KS, El-Bermawy SM, Ismail EH and Abdel-Gawad RM

abstract
The present investigation was undertaken to follow the two insect growth regulators (IGRs), diflubenzuron and chromafenozide, possible effects on the histology and ultrastructure aspects of corpus allatum (CA) of 6^th instar larvae of Spodoptera littoralis. Therefore, the LC₅₀ (3 ppm of diflubenzuron and 0.1 ppm of chromafenozide) were applied to the 4^th larval instar. The CA of 6^th larval instar treated with LC₅₀ of diflubenzuron appeared with rounded shape and decreased size (265.625 µm width & 331.25 µm length) and the capsular fibrous sheath (3.380 µm) also reduced. Contradictory, cellular cortex was increased in size (71.875 µm), as well as glandular cell numbers were increased, and their nuclei were lost their spheroid shape. Disturbance in cytoplasmic organelles pushed glandular cell to switch off or to be inactive. Also, damage was pronounced in the CA of the LC₅₀- chromafenozide treated larvae. The present work investigates the high potency and efficacy of the two IGRs towards S. littoralis corpora allata.