The walnut leaf beetle, Gastrolina depressa, belongs to family Chrysomelidae (Coleoptera), and is one of the major pests of walnut trees. G. depressa eggs were oval and dark orange. The three G. depressa larval instars were gray in color. The larval period was approx. 8.14 days ($24^{circ}C$, 16L:8D). Adults of both sexes were dark blue, and females were larger than males. Overwintered adults emerged in late April, and laid eggs in clusters on young leaves of the host tree. Mature 3rd instar larvae pupated after a short prepupal period. Adults emerged starting mid-May and entered into diapause shortly afterward.