SECTIONAL TRANSACTIONS.—D. 403 
fruitful in practical achievement as well as in entomological discovery. Practical 
achievement implies that entomological discovery has led to the elaboration of methods 
of dealing with injurious insects in the field and that these methods have actually 
been adopted by the sections of the industry concerned. This does not mean that 
the methods are completely satisfactory, but that they are sufficiently so to have 
justified their wide use by practical men. The extent of such achievement may be 
gauged by reference to some sixty species of insects, which ‘are among the most 
injurious in agriculture or horticulture. In the agricultural section, methods of 
control have been adopted successfully in some 20 per cent., tentative or partial 
measures in some 23 per cent., but there has been little practical advance in the case 
of 57 per cent. In the horticultural section, new measures of control have been 
adopted by the industry with success in 53 per cent., tentative or partial control 
measures are in use in connexion with 33 per cent., and in only 14 per cent. has little 
or no practical advance been made. 
The reason for the greater success in horticulture is economic, the horticulturist 
being able to adopt measures too costly for the farmer. 
The types of control measure may be classified as (1) Direct, in which the insect 
is destroyed by a direct attack made by chemical or other means, (2) Indirect, in 
which the environment is rendered unfavourable to the insect, either by cultivation, 
the use of resistant varieties of crop, or by the encouragement of natural enemies. 
Of the control measures successfully adopted in the cases analysed above, it is 
found that 91 per cent. are of the direct type, the majority involving the use of 
insecticides. 
It is deduced that while indirect measures may as a result of research become 
predominant in the future, the entomologist now in-practice among farmers and 
growers must rely chiefly on direct measures. 
Finally, not least among the achievements of agricultural entomology in England 
is the fact that the entomologist has largely overcome the prejudice formerly held 
against him by farmersand growers, and that he now finds in them both keenness for 
assistance and readiness to collaborate in experimental work. 
Dr. C. B. Wiittams.—The Trinidad Sugar-Cane Froghopper and 
Co-operation in Entomological Research. 
Sugar-Cane Froghopper known sixty years in Trinidad; most damage in last 
twenty-five years. Life cycle known. Usually three broods, eggs in soil and trash, 
nymphs suck roots, adults suck leaves. From point of sucking of adult damage 
spreads for several weeks but no trace of virus; requires co-operation with plant 
physiologist. Damage varies from year to year according to climate, especially 
rainfall, and from place to place according to soil, especially texture and chemical 
composition. Problems for co-operation with meteorologist, geologist, soil chemist and 
soil physicist. 
Also damage varies according to variety and age of cane and agricultural conditions 
such as drainage; problems requiring co-operation of botanist and agriculturist. 
Damage, and particularly recovery, closely related to root fungus infection, requiring 
co-operation of mycologist. 
Soil relations are particularly interesting. Always commoner on clay, heavy, 
acid, wet soils with lower pH, but spreads to lighter, less acid, soils in bad years. 
Recently experiments have shown that, when given choice, insects select heavy soil 
for egg-laying. 
Control methods tried or in progress :— 
(1) Trapping by lights.—Only catches males. 
(2) Trapping by nets.—Only possible for very short period each day. 
(3) Liming.—Very expensive, but under investigation, and most likely to produce 
permanent result. 
(4) Killing adults and nymphs with Ca(C.N). dust.—Under investigation ; appear 
to be difficulties in getting suitable duster. 
(5) Local parasite complex.—Under investigation. Mongoose sometimes considered 
as cause of damage by killing off birds, lizards, &c., but doubtful if correct. 
Green muscardine fungus, parasitic on froghopper, too dependent on climatic 
conditions, 
DD 2 
