45 



Bequet (M.), Musso (L.) & Sergent (Et.). TroisiSme campagne 

 centre les Acridiens {Schistocerca peregrina, 01.) en Alg6rie au 

 moyen du Coccobacillus acridionmi, d'H6relle. [The third campaign 

 against Schistocerca peregrina in Algeria by means of Coccobacillus 

 acridiorum.] — Bull. Sac. Path. Exot., Paris, viii, no. 9, 10th 

 November 1915, pp. 634-637. [Received 4th December 1915.] 



The campaign against locusts by means of Coccobacillus acridiorum 

 was conducted in Algeria in 1913 and 1914 for destroying the 

 native species, Dociosfaurus maroccanus, Thunb. [see this Review, 

 Ser. A, iii, p. 118]. In the autumn of 1914 a big invasion of Schistocerca 

 peregrina, 01., entered Algeria, spread through the country and reached 

 the sea in the spring of 1915, giving an opportunity for trying the 

 virus against the identical species from which it was obtained in 

 America by d'Herelle. It was found to be easy to increase the power 

 of the virus in the laboratory, the best result being obtained with 

 locusts which had died in more than four hours and less than eight. 

 Individuals which died in less than four hours may have succumbed 

 to poisoning and not to septicaemia. Each of the three authors made 

 practical trials in a different region. The total area infected amounted 

 to about 110,000 acres and about 117 gallons of spray were used. 

 The conditions varied throughout the whole period. An unexpected 

 discovery was that of the existence- — in locusts which could not 

 possibly have been contaminated in North Africa- — ^of an epizootic 

 of the same group as d'Herelle's bacillus. Though not deadly, this 

 virus is capable of having its power easily raised. The biological 

 method was found to be useful when combined with those already 

 employed in Algeria against S. peregrina and is especially advisable 

 in localities where mechanical control is difficult. It should not be 

 attempted where crops are directly threatened [see above]. The 

 instant and complete destruction of sprayed swarms must not be 

 expected, and no appreciable result is gained in the case of swarms 

 already infected with similar bacilli. The method is only applicable 

 when the locusts are feeding, that is, not before the tenth day 

 of their life, a period corresponding with the end of the third stage, 

 and the value of the results increases with the amount of bait consumed. 

 The best results were noticed in the second half of the life of the locusts, 

 during the last two stages, from the third to the sixth week. The 

 quantity of spray must be proportional to the number of locusts and 

 in inverse proportion to their density ; rather less than | pint per acre 

 may be taken as a basis. It is useless to spray a single swarm in the 

 hope of infecting all the others in a district. The disease may last 

 for a long time, but it always spreads slowly. Its spread is mainly 

 due to the pronounced cannibalism of S. 2}eregri^ia, which devours 

 the sick and the recently dead. Dessicated bodies are not touched. 

 The indigenous virus, mentioned above, was discovered before the 

 experiments were made ; it gave rise to a mild form of epizootic 

 which immunised affected individuals against C. acridiorum, so that 

 the latter produced no result in the Sebdou region. Similar infections 

 were also reported from Algiers and other places far distant from 

 Sebdou . 



