338 



KouBAUD (E,). Les Insectes et la D6generescence des Arachides au 

 Senegal. [Insects and the Deterioration of Ground-nuts in 

 Senegal] — Separate, undated, from VAnn. et Mem. du Com. 

 (TEtudes hist, et scien. de VAfrique occ. frangaise [sine loco], 1916, 

 76 pp., 14 figs. [Eeceived 30tli May 1917.] 



During tlie winter of 1913, researches were made into the causes of 

 deterioration of ground-nut crops in Senegal and as to the best remedy 

 for it. This was found to be due not to degeneration of the strain 

 owing to lack of selection of the seed, but to the ravages of insects. 

 The variety of Arachis cultivated in Senegal is wonderfully hardy, 

 perfectly adapted to the climate and soil, its selection having been 

 brought about by natural causes long ago. The two chief causes of 

 deterioration are the action of drought, the increasing lack of water not 

 being entirely due to deforestation, and the lack of measures of control 

 against insect pests. These interact and the insects mainly cause 

 damage owing to lack of water. 



The foliage is devoured by legions of beetles, crickets and grass- 

 hoppers, but the damage they do is negligible, compensation being 

 effected by the extremely rapid growth of the plant. In July and the 

 beginning of August, a small grasshopper, Conipoda calcarata, Sauss., 

 is abundant, and is replaced later by Phasmids and locusts. A 

 large grey weevil, Anaemenis fuscus, 01., occurs at the base of the 

 plants in the surface-soil. It does not attack the seeds, but sometimes 

 appears to damage the ovaries of ripe flowers and the young pods ; 

 the larvae are more destructive than the adults. A green Noctuid 

 caterpillar is very injurious, attacking the very young pods and the 

 tap-root. It can be controlled by destroying the moths by means of 

 large fires lighted at night, though this is difficult owing to lack of fuel. 

 Other pests are the larvae of Elaterid beetles, Dipterous larvae of 

 Leptidae and Empidae, Pimelia (TENEBRiONiDAE),and white grubs of 

 iheMelolonthids, Schizonycha africana, Cast., and Anomala plebeja, 01., 

 the Rutelid, Adoretus mnbrosus, ¥., and the Dynastid, Podalgus {Crator) 

 cuniculus, Burm. The plant survives injury by these when the soil is 

 moist by throwing out a dense ring of adventitious roots above the 

 point of injury, but during the dry season these cannot be formed to a 

 sufficient extent to save it. A secondary pest is the Myriapod, Peri- 

 dontopyge perplicata, only destructive in damp weather, which causes 

 the parts of plants injured by other insects to decay. The larvae of 

 the Tenebrionid beetles, Zophosis and Homala, also damage the nuts 

 developing in the ground. 



By far the most destructive underground pests are termites, of 

 which the larger species, Termes natalensis, Hav., and T. bellicosus, 

 Smeath., gnaw the pod without perforating it, though the smaller 

 Odontotennes vulgaris, Hav., attacks the nuts themselves. Eutermes 

 parvidus,Sy6&t., is also very abundant, its prevalence being due to the 

 fact that crops of ground-nuts and millet are grown alternately. 

 The natives leave the stumps of the millet stems and the refuse to 

 decompose in the ground as green manure, with the result that it becomes 

 heavily infested with this termite. E. parvulus never attacks healthy 

 plants, but only the roots damaged by other insects, and never attacks 

 the fruits when dry and ripe, but only the freshly-formed ones in search 

 of the moisture they contain. A small beetle, Scydmaenus chevalieri, 



