Abstract: Ecdysone is the insect molting hormone which induces a
series of events critical for ecdysis, beginning with the formation
of a complex between ecdysteroid receptor (EcR) and its partner
protein, ultraspiracle (Usp). We cloned a 600~bp partial cDNAs
encoding 200 amino acids EcR protein by degenerate primers from the
common cutworm, \textit{Spodoptera litura}, a destructive
agricultural pest insect in East Asia. We used this fragment to
design the EcR-dsRNA to interfere the corresponding gene to analysis
the change in different development stages. Using the Azadirachtin
(Az) feeding the RNAi injected larvae to observe the development
difference with normal control. Results indicated that the EcR RNAi
interference the normal ecdysis and result in incomplete pupal molt.
In the Az treatment after EcR RNAi injection, the larvae stunt
growth and development program were disturbed and observed abnormal
proleg phenotype. We deduced that Az and EcR RNAi maybe influence
the key genes and inhibit the ecdysone cascade modulate pathway,
which result in the disorder of tissue remodeling in
molting.

Key words: EcR, RNAi, Azadirachtin, Spodoptera litura., proleg phenotype