SECTION VI. — NATURAL ENEMIKS OF THE FROGHOPPER. 69 



November 1914) he obtained 210 eggs from one female in sixteen days, 

 142 of which were laid in the first ten days. Guppy also found that 

 eggs from unfertilised females did not hatch. 



In the moister parts of the island the insect breeds throughout the 

 year, but in the cane fields it is seldom, if ever, seen before the beginning 

 • of the wet season, and usually does not become common until the 

 second or third brood of froghoppers are in the nymphal stage (August 

 to Octuber). The first adult was seen in the cane fields in 191B on 17th 

 June and in 1919 on 1st July. By October and Novenjber it is usually 

 pejssible in thickly iiifested fields to find a Syrphid maggot on almost 

 every stool, and on one occasion in November 191fS I found four maggots 

 in fifty froth masses examined. 



It is not known how or in what stage they survive the dry season in 

 these localities or to what extent restocking takes place each year by 

 migrations from the nioister districts. 



Up to the present the Syrphid fly has been found on T. saccharina 

 in Trinidad, T. pubescent in Trinidad and British Guiana, T. fiavi^ateta 

 in Bi-itish Guiana, T. carmodyi in Tobago, on another unidentified 

 species of Toinaspis in the North- ^^'est District of British Guiana, and 

 en two unidentified species in Costa Rica. 



In addition to these localities where the host is known, it is recorded 

 from Mexico, Guatemala, Panama, and Brazil, which indicates a very 

 wide range in which it probably parasitises many other species of the 

 genus Tomaspis. 



It is in its turn destroyed by enemies, the chief of which are 

 appai-enbly spiders. Guppy in Tobago found a larva which pupated and 

 from the pupa three Oligochaete worms emerged. 1 submitted one of 

 those to Mr. P. S. Welch of the University of Michigan and he identified 

 it as an immature specimen of one of the Enchytraeidce {Olifjochaeta). 

 He suggested that as no similar worms have ever been recorded as 

 parasitic on insects their position as parasites of Salinngogaster should 

 be questioned until further corroborating evidence is obtained. 



In view of the value of the Syrphid fly as a froghopper control, and 

 of its scarcity in the cane fields during the earlier broods of the froghopper, 

 Kershaw recommended an attempt to breed it through the dry season in 

 large numbers so that specimens could be liberated early in the wet 

 season in the localities likely to be infested with froghoppers. During 

 1913 and 1914 Guppy attempted to carry out this suggestion. In 

 October 1914 he distributed 400 eggs, in November 500, and 200 in 

 December. Dining the dry season however the difficulties were so 

 great, with the funds and assistance available, that the work was finally 

 abandoned. He has given (1914 B.) an account of these experiments, in 

 which he mentions tlie impossibility of obtaining sufficient froghopper 

 nymphs during the dry weather to keep alive more than a very 

 limited number of Syrphid maggots, and also the difficulty of saving the 

 auult flies fiom the persistent attacks of spiders. 



The method, even if it were possible and successful from an economic 

 point of view, suffers from the disadvantage that it would have to be 

 repeated evei-y dry season. 



Ants. 



It has been mentioned above (p.,t60) that the froth of the nymph 

 protects it almost entirely from the numerous species of hunting-ants 

 which infest the ground in the cane fields. 



