Archarius crux is a small (2.2-.7mm) weevil until recently classified in the genus Curculio. The larvae develop on willow (Salix) in the galls of wasps of the genera Pontania and Euura. The female will bore into the gall and usually eat the larva of the wasp befor depositing her egg in the created hole. If not, the weevil larva will later consume the wasp larva. Mature larvae will leave the gall and pupate in the ground. Adult weevil will feed on the leafs of the willow tree.