54 



comparing them a conclusion may be reached as to whether the bird 

 is harmful or beneficial to agriculture. These methods are applied 

 in detail in the case of the rook, which has been becoming increasingly 

 abundant in Britain of recent years. From the figures given it is 

 estimated that 10, 000 of these birds consume in a year about 232 tons 

 of food, and in obtaining this they destroy about 80 tons of cereals, 

 32 tons of potatoes and roots, 7h tons of beneficial insects, and 65 tons 

 of injurious insects, slugs, snails, etc., the rest of their food having 

 no economic importance. It is not considered probable that this bulk 

 of injurious insects, if they had not been destroyed by the rooks, would 

 have done as much damage as the latter, as a considerable percentage 

 would have been eaten by starlings, jackdaws and black-headed gulls. 



On the other hand the large amount of cereals destro^^ed is thought 

 to be due to a change in food preference, following on the increase in 

 the rook's numbers. In all probabihty there are too many rooks 

 feeding on the same food in a given area, and that which is most 

 plentiful and most easily procured is taken. 



Even when reduced in numbers the rook would still feed on cereals 

 to a certain extent, but the percentage would be lower ; and it would 

 benefit the farmer to lose such a percentage in order to have destroyed 

 the greater percentage of injurious insects, many of which, such as 

 wireworms, leather-jackets, ground caterpillars and weevils, could 

 not be so thoroughly or economically attacked in any other way. 



Repressive measures are, consequently, recommended, but not 

 reckless and wanton destruction, so that the rook may be brought 

 back to its normal position, in which it is one of the most useful of 

 birds. 



ScHLUPP (W. F.). Mylabris Beetles. — Jl. Dept. Agric, Union S. Africa, 

 Pretoria, i, no. 8, November 1920, pp. 741-749, 3 figs. 



A short account is given of the life-history and economic status 

 of bhster-beetles (Meloidae) in various parts of the world, and of 

 the preparation and properties of cantharides. In South Africa the 

 beetles injure the flowers of fruit trees, beans, peas, etc., but it is 

 doubtful if the setting of the fruit is interfered with, and their numbers 

 and the damage they do is often greatly overestimated. If severe injury 

 is done, however, the beetles should be destroyed. Even if their larvae 

 do attack grasshoppers (which is uncertain), the latter feed chiefly 

 on grasses on the veldt that are of small value compared with the crops 

 the beetles destroy. Spraying is not a satisfactory method of destroying 

 the beetles, but systematic hand-collection is much more effective than 

 might be expected. The cool, early morning is the best time, as the 

 beetles are then least active. They may be disposed of by dropping 

 them into water on which a little paraffin oil is floating. 



The commercial possibihties of these beetles in South Africa are 

 negligible. The demand for cantharides is very limited, and though 

 the South African species yield a larger amount of cantharidin than the 

 " Spanish ¥\y," Lytta {Cantharis) vesicatoria, they are not, like it, 

 gregarious, so that the labour involved in collection would be many 

 times as great. It takes a thousand dried beetles to weigh a pound, 

 and even where the beetles appear fairly numerous there are probably 

 only about half that number to an acre. If it should ever become 

 worth while to use them for commerce, they are best killed with carbon 

 bisulphide. 



Of the Meloidae observed in South Africa the most numerous 

 are Mylabris oculata, M. liinata, and Cyaneolytta subcoriacea. 



