18 FROGHOPPER BLIGHT OF SUGAR-CANE. 



be scarcely possible to distinguish the two when alive. This abundant 

 species would not touch the eggs of the froghopper and was probably a 

 parasite of some species of leaf-hopper. 



Under normal conditions I should have proceeded from Panama to 

 British Honduras as had been arranged, but by this time travelling had 

 become so difficult owing to the withdrawal of ships, that I reported 

 that it would be almost impossible to transfer to Trinidad any parasites 

 that I might discover there, until such a time as travelling facilities 

 improved. 



In view of this and of the indications obtained of the necessity of 

 going still further afield in the search for parasites, it was decided to 

 stop this work temporarily at least, and I returned to Trinidad, visiting 

 on the way Carthagena, Columbia, where I found Toviaspis lepidior. 

 previously seen in the Canal Zone, and the islands of Martinique and 

 St. Lucia in the West Indies, in neither of which were any froghoppers 

 found. 



INVESTIGATIONS FROM AUGUST 1917 TO MARCH 1920. 



On my return to Trinidad in July 1917, I was instructed by the 

 Froghopper Committee to continue work in that island, to study the 

 froghopper from a wide biological standpoint, and in particular to see 

 if any reason could be found for the great increase of damage by the 

 froghopper in recent years. It was desirable to find if this was 

 connected in any way with the increased use of seedling canes less 

 resistant that the original Bourbon cane, or if the increase in numbers of 

 the froghoppers was due to the supposed reduction of their natural 

 enemies by the spread the mongoose, first introduced into the island 

 about 1870l 



The present report gives as completely as possible the results of my 

 experiments and investigations from August 1917 to March 1920. The 

 greater part of this time was spent in Trinidad studying the agricultural 

 aspect of the blight, but in December 1917 I was able to visit the island 

 of St. Vincent for a few days, to see if the froghopper existed there 

 but in the time that could be spared, no specimens were found 

 (see p. 44). 



In August 1918 I \isited Barbados on sick leave find while there 

 took the opportunity of discussing with Sir Francis Watts, Imperial 

 Commissioner of Agriculture for the West Indies, some of the problems 

 of soil chemistry involved in my investigations, and with Mr. W. Nowell, 

 Mycologist to the Department, the question of the relation of root- 

 fungus and froghoppers in the production of blight. As a result of this, 

 Nowell visited Trinidad in December 1918 to January 1919 and again in 

 October to November 1919 to co-operate with me. The results of his 

 work, have been published in two reports (see bibliography) and he did 

 much to clear up the complexity of this branch of the work. 



It is hoped to issue at a later date a full sj'stematic account of the 

 species of the genus Tomaspis met with during these investigations, and 

 a classification of the genus based chiefly on a study of the habits and 

 an examination of the structure of the genitalia. 



ACKNOWLEDGMENTS. 



In addition to acknowledging my indebtedness to the authors of the 

 published records mentioned above or in the bibliography I wish to take 

 this opportunity of expressing my thanks to a large number of gentle- 

 men without whose assistance the completion of this work would have 

 been impossible. , 



