42 INSECTS AND VEGETABLE PARASITES INJURIOUS TO CROPS Scale insects Difficulty of combating the aphides in the Sudan Value of lady Bird beetles of the leaves, hindering the plant respirations by their secretion, and destroying the young ears of grain while they are yet soft. It is easy to recognise an infected plant from the shiny stickiness on the leaves, the deposit on the ground, sometimes very copious, and the vast number of pale larvae and so-called plant-lice. The acacia arabica, (sant tree), is liable to be attacked by a scale insect which forms little white balls on the twigs. Specimens of this and of all the Aphides have been sent to Mr. Theobald. The acacia insects were given me by Mrs. Broun, the Honorary Secretary of the Museum Board. She had collected them on the White Nile.

The Aphis has formed the subject of several reports to the Secretary General, but it is evident that in a country like the Sudan it is very difficult to employ suitable preventive methods. No doubt petroleum, naphthalene and quassia washes and sprays are effective, but they have to be properly and judiciously applied, and in many cases spraying apparatus would be required. Burning of infected grain would be beneficial, the planting of the castor-oil plant round the fields is said to be useful, and something might be accomplished by merely squirting water through a hose on the plants and thus washing off the insects, but the outlook is scarcely hopeful in this direction. The question of the utility of lady-bird beetles, (Coccinellidae), which along with their larvae feed greedily on the Aphides, is an important one. Mr. Broun noticed a lady-bird busy on infected plants in the Bahr-El-Ghazal. I found fragments of lady-birds in the dura specimens from Kassala and Sennar, and discovered the following species present in large numbers on the “ Asal ” dura in Khartoum. Mr. Theobald kindly identified them for me as— Chilomenes vicina, Muls. Coccinellct. 11 -punctata.

Specimens of these were secured and mounted and entomologists in South Africa were communicated with, as American lady-birds have been introduced there to combat Scale Insects and Aphides.

The information obtained has been sent to the Secretary General, and it is probable that in the Coccinellidas, either those which are indigenous or species which may be imported, we have the best means of attacking the fly. At the same time it must be confessed that the reports received are none too encouraging. The Aphides are themselves liable at times to invasion by a fungus (Entomoplitora aphid is), which destroys them wholesale. It seems worth while considering if this could not be utilised, but the whole question is really one for a skilled entomologist. It will no doubt receive due attention from the official recently appointed for the purpose by Lord Cromer. Meanwhile information has been furnished with regard to appropriate washes and how they are best employed, and here again I would express my indebtedness to Mr. Theobald, to the Agricultural Bureau at Washington, U.S.A., and to the South Eastern Agricultural College at Wye, Kent, England.