Résumé: This research aimed to assess the chemical composition of the essential oil (EO) of Thymusmunbyanus subsp. coloratus cultivated in Annaba (Northeast Algeria) and to evaluate its potential insecticidalactivity against newly molted pupae of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). The yields of EOcalculated from the dry matter of the aerial part of the plant were estimated at 2.56 % (w / w). Its chemicalcomposition has been analyzed using gas chromatography/mass spectroscopy (GC / MS). 54 Compoundswere identified and the main components were carvacrol (39.11 %), para- cymene (15.47 %), and thymoquinone(10.59 %). In preliminary bioassays, various doses (5, 15, 25, 40, and 100 μl / mL) of the T. munbyanus EOwere tested on newly molted pupae and the inhibition doses (ID) of adult emergence were determined. In afollow-up experiment, EO of T. munbyanus applied at its ID25 (15.38 μl / mL) and ID50 (25.22 μl / mL) wasevaluated on acetylcholinesterase (AChE) and glutathion S-transferases (GSTs) activities. Biomarkersmeasurements in the treated pupae and adults (ID25 and ID50) revealed an inhibition in AChE activity andactivation of the detoxification system as evidenced by induction in GSTs activities. Lastly, our results provedthe potential use of this material as an alternative to synthetic insecticides for controlling stored product pests.Keywords: Biomarkers, Ephestia kuehniella, Essential oil, GC / MS, Thymus munbyanus.

Résumé: The current study examined the lethal and sublethal effects of azadirachtin on pest of stored food Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). Firstly, several doses were tested by topical application on newly molted pupae and the doses of inhibition (ID) of adult emergence were determined then, two doses, 0.42 µg/ pupa and 1.06 µg/pupa, corresponding to ID25 and ID50, the doses required for 25 and 50% inhibition of adult emergence, respectively. They were tested on different development parameters and cuticular thicknesses during metamorphosis. Results showed that azadirachtin significantly increased the duration of pupal development and decreased pupal weight. In addition, treatment disrupted metamorphosis and several morphogenetic types have been observed (malformed adults, partial molt and blocked molt). Lastly, azadirachtin also affected cuticular secretion by reducing the thickness of the old and the new cuticle at different ages during metamorphosis. Key words : Azadirachtin, cuticle secretion, development, Ephestia kuenniella, molting disruption.