C. pipiens will oviposit in the laboratory after feeding on a variety of substances, some of them purely vegetable, without having a blood meal. In most cases the ova thus obtained are viable. Better results are obtained in such experiments with adults bred from larvae grown on rich food, such as a solution of haemoglobin. In one case a [female] laid viable eggs within 18 hours after hatching and without having taken food of any kind.