SECTION VI. — NATURAL ENEMIES OF THE FROGHOPE'ER. 87 



It will be seen that the fungus has never been found before October 

 but may persist for a short time into January. 



The rate of infection of adults as indicated by laboratory experiments 

 is extremely i-apid. Healthy specimens were confined in a cage with 

 ■diseased ones on 4th November, 1919 and one was dead and showing 

 distinct signs of Empitsa fungus thirty six hours afterwards on the 

 6th November. 



Unfortunately this Empusa, unlike the green muscardine, can only 

 be cultivated with very great difficulty off the host insect, and even in 

 this it is exceptional as most other species of Empusa cannot be 

 artificially cultivated at all. 



Acting on some suggestions of Mr. Rorer I made an attempt in 1917 

 to cultivate the fungus and carry it over the dry season in order to 

 distribute it in the beginning of the following wet season. 



On 17th November, 1917 I inoculated from an infected insect two 

 culture tubes of agar and six potato tubes. By the 8rd December 

 (sixteen days) one of the potato cultures had a thick mycelium growth 

 and was shooting off spores on to the side of the tube. By 15th 

 December several other of the potato cultures were producing spores, but 

 those on the agar had failed to do so. 



Transfer cultures were taken on fresh potato tubes from these spores, 

 but they gradually died off and failed to produce a further supply of 

 spores. It is probable, that in order to carry on the culture, alternate 

 generations at least would have to be grown on the insect to keep up 

 the vigour of the strain. 



The fungus, or a similar one, has been recorded in Mexico on frog- 

 hoppers by Urich (1913 B. p. 247). In Trinidad nothing further is 

 known of its liabits or any other hosts. 



HYPEHPARASITES. 



Under this heading will be considered those animals which prey on 

 the enemies of the froghopper, and by reducing their numbers allow the 

 froghopper to multiply. 



The Mongoose. 



Since its introduction into the West Indies about 50 years ago the 

 mongoose has been a subject of debate and dispute. 



It was originally imported without the slightest atteuipt to get first 

 an accurate estimate of its food, and after being greatly praised for 

 ,\ears for its effective destruction of rats, it has grtulually become the 

 scapegoat which receives the blame for every outbreak of every pest 

 in the West Indies, among which must be included the froghopper at 

 present under consideration. 



As mentioned on p. 18. I was in 1917 instructed by the Froghopper 

 Committee to find out if possible to what extent the mongoose was 

 responsible for the recent outbreaks of frogh3p2:)ers. 



In order to do this, two lines of work were necessary (1) to get an 

 accurate history of the outbreaks of froghopper blight in Trinidad and (2) 

 to get an accurate knowledge of the food of the mongoose. 



The history of the blight so far as can be ascertained has been given 

 in Section III. 



The investigation of the food of the mongoose was started in 1917 

 and carried on for a year, the results being published in a separate 

 report (Williams 1919 A.) 



With these facts we can proceed with the original inquiry. 



