99 



practical application of the bacillus in lar<;e rpiantities was successfully 

 carried out, the results being analogous to those obtained in the experi- 

 mental campaign |see this Review, Ser. A, iv, p. 45]. Spraying with 

 the virus of ('. acridiorum invariably created an epizootic amongst 

 the swarms of Schistocefca peregrimi. In no case did this epizootic 

 cause the ctxnjilete disai)pearance of the infected swarm, but it was 

 marked by a more or less considerable daily mortality. Where the 

 ground Jiad a unifonnly level surface, the disease was disseminated, 

 while it was centralised in broken ground attbrding the shelter of trees, 

 hedges, etc. Infection is never carried for more than about 1 kilometre 

 in the direction followed by the locusts, a swarm proceeding over 

 vmiform ground becoming inmuinised. It would appear, though this 

 cannot be affirmed with certainty, that sprayed swarms cease to travel, 

 and this occurs even where the incidence of the infection is 

 inconsiderable. 



Vku;(H.)- La. Lutie contre Schfstocercd peregrina au Maroc en 1916 

 par la m6thode biologique. Deuxieme campagne d'exp6riinenta- 

 tion. [Control of Schistocerca ■peregrina in ^Morocco in 1916 by the 

 Biological Method. Second experimejital Campaign.]— BuZ/. Soc. 

 Pa!h. ExoL, Paris, ix. no. 9, 8th November 191G, pp. 682-681. 



The experimental campaign of 1915 proved that Schistocerca peregrina 

 could be most successfully controlled at the period when the locusts 

 live in a compact mass and cannibalism is at its height [see this 

 Review, Ser. A. iv, p. 46]. During 1916, practical experiments based 

 on the conclusions reached weie carried out. The first swarms of 

 locusts arrived in November and December around Souss and Agadir 

 and spread rajiidly (eastward, and more slowly northward, where climatic 

 conditioiLs are less favourable. By the end of .July, the last swarms of 

 the second generation had disappeared southwards. All swarms 

 passing through Chaouia were attacked by a virulent CoccobaciUus, 

 the disease increasing undei- unfavourable climatic conditioas. The 

 conclusions were reached that it is impossible to increase the virulence 

 of American stock CoccobaciUus, preserved in vitro since the previous 

 July, and that locusts hatched during the passage of contaminated 

 swarms, are themselves contaminated. After May, the increase in 

 virulence was normal. Spraying was carried out in various regions, 

 320 gallons being used of fresh mixture (24 to 36 hours) which caused 

 death in six hours by inoculation in the laboratory. Results showed 

 that the most favourable moment for contamination is the end of the 

 3rd instar, when the locusts form a compact mass. Contagion is then 

 fatal and results in almost total destruction of the. infected swarms 

 From the 4th instar, the propagation of infection is much less certain ; 

 the colunms are less dense, a greater distance is covered each day, while 

 the diseased insects drop to the rear of the swarm and die isolated. 

 Towards the last moult the swarms thus become largely freed from 

 infected individuals ; for this reason the last larval periods are not 

 favourable to the application of this method, especially in open country. 

 The ideal conditions for the application of d'Herelle's method are so 

 difficult to obtain that it cannot be considered by itself a solution 

 of the problem, although its economic value, when practicable, is 

 uadoubtei. 



(C3d4) &2 



