1. Algae are ingested by many species of mosquito larvae and appear to form an important part of the food of these larvae.
2. The algae are digested in the gut, but the digestion is often by no means complete.
3. It is quite possible that the rôle played by the algae may also be assumed by other forms of organic matter, for larvae may be reared to maturity in solutions containing little or no algae.
4. Different algae react differently in the guts of the larvae, some being noticeably digested and some hardly at all.
5. Those algae which are digested the most are easily stained and are forms of low osmotic pressure.
6. Cytological investigation revealed no character that indicates that algae are an especially nutritious diet.
This work was carried out at the Farnham House Laboratory of the Imperial Institute of Entomology, Buckinghamshire, under the guidance of Dr. P. A. Buxton, to whom my thanks are due.