Corpora allata (CA) volume was used as an indicator of the juvenile hormone (JH) level (Pflugefelder 1948). Larvae were dissected every 24 h and until prepupal stage after treatment with E. coli (G-), B. thuringiensis (G+) at concentration of 1.5 ppm and control. The method of Armstrong and Carr (1964) was used to calculate the CA surface area.