16 FROGHOPPER BLIGHT OF SUGAR-CANE. • 



and in his final report he emphasised the importance of control by 

 natural enemies, and recommended among other things, that an 

 attempt should be made to breed the Syrphid fly artificially on a large 

 scale, and that, at the same tniie if possible, a search should be made 

 abroad to find new enemies, which might be introduced into Trinidad. 

 He made some careful anatomical studies of the Froghopper and was 

 the first to show that the Tobago species was difterent from that in 

 Trinidad. 



THE SEARCH FOR PARASITES IN CENTRAL AMERICA. 

 May 1916-Jln-k 1917. 



For eighteen months after the departure of Kershaw, Grui)py 

 attempted to breed the Syrjihid fly on a large scale, but the work was 

 found to be impracticable and was finally abandoned in 1915. 



Attention was then directed towards the second of Kershaw's 

 recommendations — that an efficient parasite be sought for outside 

 Trinidad. In December 1915 it was decided to proceed with this, 

 unfortunately, however, on a very limited scale, and in February 1916 

 I was appointed to can-y out this work, with instructions to proceed 

 to Trinidad, and from there to A'isit such neighbouring colonies and 

 foreign countries as might be likely to contain fresh parasites of the 

 froghopper. 



As very little was known of the distribution in Central America of 

 the various species of froghoppers and their parasites, and as conditions 

 arising out of the European War had already- begun to effect travelling, 

 it was decided to commence work close at hand. Therefore, alter a few 

 Wv eks in Trinidad to familiarise myself with the conditions in the sugar 

 fields there, I proceeded to Surinam (Dutch Guiana) where I was able to 

 visit sugar fields for a few hours and to nif'ke a hurried study of a 

 species of froghopper (Tomaspis tristia) reported as slightly injurious to 

 sugar-cane in that country. A short report on that insect has already 

 been published (Williams 1917, see also p. 46). 



From Surinam I proceeded to British Guiana and spent thei-e f lur 

 months investigating chiefly two species of Tomaspis, one of whi^h, 

 Tomaspis flavilater a, Urich, was common in the canes in the coastal 

 district of Demerara and has since pi'oved itself capable of sevei-e 

 damage : the second species, at present unnamed, was abundant on a 

 wild grass {Impernta caudata) in the rubber plantations at Issororo, 

 North West District, and was studied chiefly on account of its very 

 close resemblance to the Trinidad insect, from which it is only separated 

 with difiiculty. A report on the first of these two species has 

 already appeared ("Williams 1918 B.), the second portion is still 

 awaiting an opijoi-tunitj' for identification of the insect itself and various 

 insects associated with it. 



From the point of view of the introduction of new enemies into 

 Trinidad, the investigations in British Guiana had no practical result, 

 as I found there nearly all the parasites and predators already known in 

 Trinidad, although attacking different species of froghoppers. The work 

 indicated that the distribution of the parasites was wider than that of 

 their hosts and that in consequence it would be necessary to go further 

 afield in order to find new enemies. 



I returned to Trinidad in October 1916 and shortl3" afterwards paid a 

 short visit to the island of Tobago, twentj'-two miles North-east of 

 Trinidad, to confirm the report that the froghopper found there was not 

 the same as the Trinidad species. 



