In 1945 I received a large collection of Streblidae from the late Prof. A. M. Adamson, of the Imperial College of Tropical Agriculture. This collection was made by a post-graduate student, Mr T. S. Jones, and Dr E. C. Humphries, in Trinidad. Later on Mr Jones sent me another three collections, which together with the first comprised three hundred and sixty specimens, the largest number of Streblidae which has ever been collected in America. In addition, I received seven specimens from Mr P. C. J. Brunet, of Keble College, Oxford, which were also collected in Trinidad. I take this opportunity to express my thanks to all these gentlemen, and especially to Mr Jones, who also supplied me with the list of the bats of Trinidad, and some useful information regarding their roosting habits. My thanks are also due to Dr T. C. S. Morrison-Scott and Mr R. W. Hayman of the British Museum (Natural History) for their help in checking the names of several species of bats. The present record is based on the abovementioned five collections and also includes all those records which had been known from Trinidad before.

A new virus affecting cruciferous plants is described and the name suggested for it is the turnip yellow mosaic virus. The virus is sap-transmissible and has a dilution end-point in extracted sap of 10−5. The thermal inactivation point lies between 70 and 75° C.

The virus is not transmitted by insects with sucking mouthparts, but the insect vector in nature is a flea-beetle, Phyllotreta sp. More than one species of flea-beetle can transmit the virus.

Under experimental conditions the virus has been transmitted by the mustard beetle, Phaedon cochleariae and its larva; by the ‘long-horn’ grasshopper, Leptophyes punctatissima Bosc.; by the ‘short-horn’ grasshopper, Stauroderus bicolor Charp. and by the common earwig, Forflcula auricularia Linn. Lepidopterous larvae have, so far, failed to transmit the virus.

The relationship of the virus with biting insects is discussed.

Turnip yellow mosaic virus has been obtained from several cruciferous plants as a nucleoprotein of the pentose type. It crystallizes from salt solutions as isotropic octahedra and from 20% alcohol at pH 3·7 as birefringent needles. On centrifuging out of solution the pellets are also crystalline. The virus preparation contains some 22% of nucleic acid.

The virus is denatured at room temperature in alcohol of concentration greater than 30% in neutral solutions, and the nucleic acid, which is a large polymerized particle, is liberated.

The preparations have been found to consist of 80 % of a nucleoprotein and 20 % of a nucleic acid-free protein which may be isolated by high-speed centrifuging. The latter has the same electrophoretic mobility and isoelectric point (pH 3·7) as the nucleoprotein; both crystallize in the same crystal form, and they are serologically identical.

The nucleic acid-free material does not seem to be infectious.