498 



author's opinion there can scarcely be any doubt that individual 

 insects may also be immune from attack. These circumstances 

 explain why Ichneumonids often prove unsatisfactory as a check. 

 When reared in captivity, their increase is usually far from rapid, and 

 the individuals thus obtained are inactive when released among 

 host-insects. In spite of these limitations Ichneumonids still play 

 an important part against insect pests ; for instance, an outbreak of 

 Rhyacionia (Evetria) resinclla, Ij., in north Brabant was checked in 

 this maimer some years ago, 98 per cent, of the galls collected during 

 the last year of the outbreak being parasitised, probably by Glypta 

 resinana, Htg., and Macrocentnis ahclominalis, F. 



Sprenger (A. M.). De Bestrijding van Insecten met Arsenicum- 

 praeparaten en het Gevaar voor de Bijenteelt. [The Use of 

 Arsenic«j,ls against Insect Pests and the Danger to Bee Farming.] 

 — Tijdschr. Plant enziekten, Wageningen, xxiv, no. 3, May 1918 ; 

 Bijblad, pp. 21-25. [Keceived 3rd September 1918.] 



The spraying of fruit trees in blossom appears to be highly successful 

 against insect pests, but the arsenical preparations used are dangerous 

 to bees and many swarms have been destroyed owing to the drippings 

 from the trees contaminating the Leguminosae growing beneath 

 them. In 1916 bees in the currant plantations of Zeeland were killed 

 by the Urania green solution employed against Pteronus rihesii 

 (Nematus ventricosus) (currant and gooseberry sawfly). It is therefore 

 important to find an efl&cacious insecticide which will be harmless 

 to bees. Barium chloride has been placed on the market under the 

 name of " Ventricosus-powder " and a 2 per cent, solution is said 

 to destroy the pests without affecting bees. This remedy is not, 

 however, a new one, nor does it appear to be harmless, as bees fed 

 with honey containing 2 per cent, of barium chloride seemed to be 

 affected thereby. 



KiTZEMA Bos (J.). Aardvlooien. [Flea Beetles.]— Tijdschr. Planteur 

 ziekten, Wageningen, xxiv, no. 3, May 1918 ; Bijblad, pp. 36-40. 

 [Received 3rd September 1918.] 



This is a popular article and states that a good method of combating 

 these pests is to strew infested fields with sand with one-fifth of its 

 volume of petroleum added and w^ell mixed in. This repels the insects 

 for about five days, by which time the young plants should be able 

 to resist attack. If this is not the case^ the treatment must be repeated. 



ScHENK (P. J.). In en op den Bodem levende Plantenvijanden, I. 



[Plant Enemies living in or on the Ground. I.] — Tijdschr. 

 Plant enziekten, Wageningen, xxiv, no, 4, July 1918, pp. 149-159, 

 2 figs. [Received 3rd September 1918.] 



This paper deals with the following ' Melolonthids occurring in 

 Holland :- Melolontha melolontha, M. hippocastani , Amphimallus 

 (Rhizotrogus) solstitialis, Polyphylla fullo, and Phyllopertha horticola. 

 M. tnelolontha is found chiefly in the eastern provinces, while 

 M. hippocastani is more limited to the western ones. The former 

 species is mainly responsible for outbreaks recorded ; it is said to 



