Vol. XV. No, 379. 



THE AGRICULTUEAL JJEWS 



363 



■weather was ■ot rainy, an interval of seven or eight days, 

 never more than ten. was allowed between the applications. 

 This comparatively short interval was made possible by the 

 great immunising power of the covering film, especially that 

 left by the second application, which prevented attacks by 

 larvae from the few surviving adults. It is most important 

 that the spray should not be stinted, as a uniform coating is 

 the object aimed at. The spray-nozzle should be at an angle 

 of 45° to the rod. . 



THE SILKWORMS OF AFRICA. 



The only silkworms of comiiifrcial importance found in 

 a wild state in Africa belong to the genus Anaphe (family 

 Eupterotidae). The chief species occurring in British 

 territory are A. tnfracta, Nigeria and Uganda; A. venata, 

 Nigeria and Gold Coast; A Moloneyi, Nigeria, A. ambrizia, 

 Uganda; A panda and A. reticulata, IS^atal. The cocoons of 

 all these species are spun in masses, which are enclosed in 

 & silken nest. The latter varies in size and shape according 

 to the species; it may be hollow and more or less spherical, 

 as in the case of A. ivfracta and A. venata, or flat, as in the 

 case of A. Moloneyi. The envelope of the spherical nests 

 usually consists of three layers: the outermost more or less 

 papery in texture, the middle portion composed of loosely spun 

 silk arj-anged as a number of super imposed sheets, and the 

 inner layer hard and parchment-like; that of the flat nests con- 

 sists of a single papery layer of closely interlaced silk. The 

 silk of both nests and cocoons is naturally brown in colour, 

 but in the absence of light the wt)rms produce a white silk, 

 and for this reason the natives in parts of Nigeria sometimes 

 enclose them in calabashes. 



Anaphe silk cannot be reeled, as is done in the case of 

 mulberry silk, and it is therefore carded and spun as 'waste' 

 silk; but apart from this, it more closely resembles mulberry 

 silk than does any other kind. It takes dyes well and has 

 been found suitable for the manufacture of velvet, plush, 

 sewing silks and other materials. The degummed silk 

 has been valued at about Is. per B)., bat owing to 

 the large amount of labour required to free the silk from 

 extraneous matter, and the low yield of degummed 

 silk, the crude material, if shipped to the United 

 Kingdom, would only realize about \d. or 2rf. per fi). If, 

 however, the silk were cleaned locally by the natives, the 

 clean product might be worth M. per lb. in this country. 



The main difficulties in the way of establishing an 

 Anaphe silk industry are (1) the fact that the nests have to 

 be collected one by one over a large area, (2) the cost of 

 cleaning the crude silk, and (3) the bulkiness of the material 

 for export. These difficulties can be overcome to some extent 

 as follows : (1) by domesticating the silkworm so that the 

 cost of collection is reduced (and it has been shown experi- 

 mentally in Uganda that the worms can be successfully dom- 

 esticated ); (2) by removing all chrysalides, twigs, etc., from 

 the silk on the spot by native labour; and (3) by compressing 

 the resulting clean product in ba%3 for export. So long as 

 the existing rjs^hods of collection prevail, it seems extremely 

 doubtful whether the industiy can be a success; but if the 

 methods suggested above for rerlucing the cost of production 

 were carried into effect upon a sufficiently large scale, and 

 the cleau pioJact shipped to Europe, tliere seems to be no 

 rea.son why a new industry, contributing to the welfare of 

 several of our African possessions, should not be established. 

 (Bulletin of the Imperial Institute, Vol. XIV, No. 2.) 



A Pest of the Horse Bean.— Daring September 

 a communication was received at this Office from the 

 Agricultural Department, Grenada, referring to a pest that 

 had been discovered attacking the foliage of horse beans. 

 The caterpillars which were causing the damage were 

 observed to resemble very closely in colour that of the 

 particular foliage they were feeding upon. They were 

 observed to cling to th. undersides of the leaves and, when 

 disturbed, they dropped to the ground with what appeared t* 

 be a springy motion that often caused them to reach the 

 ground some little distance from the spot vertically beneath 

 the part of the plant on which they were feeding when 

 disturbed. The letter points out that these peculiarities of 

 the insect may account for their not having been discovered 

 before. 



Accompanying the letter were several moths bred out in 

 Grenada from »he caterpillars. These moths were identified 

 at this Office as examples of Thermeda digitalis, the well- 

 known woolly pyrol moth, the larvae of which are very 

 destructive of the foliage of many leguminous herbs (woolly 

 pyrol, various beans, and ground nuts). The later generation 

 (after they have become abundant) are usually heavily 

 parasitized; lead arsenate might be used if it were worth 

 while, but a preliminary experiment would be needed to 

 find what strength was non-injurious to the plants. 



GREEN MANURES AND MANURING IN THE 

 TROPICS, by P. de Sornay, Translated by F. W. Flatteley, 

 London: John Bale, Sons & Danielsson, Ltd., 1916. Pp. 

 466, Figs. 74. Price 16s. net. 



The title of the original French edition of this work is 

 Les Plantes Tropicales Alimentaries et Industrielles de la 

 Famille des Legumineuses, which was reviewed in the Agri- 

 cultural News last year in Vol. XIV, No. 341, on page 165. 

 The English title is less significant than the French, in view of 

 the fact that it refers merely to a portion of the range of 

 subjects dealt with. Reference to the previous review wiH 

 furnish the reader with an idea of the contents, which 

 include, besides an account of the tropical leguminosae in 

 relation to manuring, lengthy accounts of the species useful 

 as human food, discussions on prussic acid in the leguminosae, 

 also starch, gums and resins, tannins, dyes, medicines and 

 fibres, etc. 



The work consists essentially of a compilation of facts 

 carefully collected and arranged in a manner that facilitates 

 reference. Special attention may be called to the excellent 

 illustrations. An interesting feature of the book is the favour- 

 able opinion expressed of the Canavalias as bean crops. In 

 the West Indies, the Canavalias for food purposes are regarded 

 with a considerable amount of suspicion. Altogether the 

 number of species of leguminous plants referred to in the 

 book is 366 out of the 7,000 known to science as belonging 

 to the order. 



