292 Annual Report for 1912 of the Zoologist. 



in this country is rather curious. The few references to it 

 to be found in works on economic entomology allude to it as 

 Thrips pisivora, a name to which it has no claim. It is true 

 that Professor Westwood so called it in an article in the 

 Gardeners' Chronicle in 1880 {?), but he did not formally 

 describe it, and the species is, therefore, merely nominal. 

 Indeed such description as he does give seems to be founded 

 chiefly on the larva. Until recently it has remained doubtful 

 whether there is any pea-thrips par excellence, or whether peas 

 are subject to the attacks of various members of the group, 

 but that matter has been set at rest by our investigations at 

 Cambridge. There is certainly one species which especially 

 infests peas, and that species has been identified for us by 

 Mr. C. B. Williams, of Rothamsted (who has paid particular 

 attention to this group of insects) as Frankiniella 7'ohusta. In 

 the Report of the Zoologist for 1908 the results of a partial 

 investigation into its life history were given. The eggs 

 were found, not loosely in the flower as previously stated, but 

 embedded in the substance of the stamen-sheath, and there the 

 larvae were found in different stages of development till they 

 emerged to feed upon the growing pod. Moreover the injury 

 was shown to be caused by the insects sucking the sap of the 

 pod— not by gnawing away its substance. 



With the aid of Mr. Maulik, an advanced student at Cam- 

 bridge, further investigations have been carried on during the 

 past season. These have for the most part confirmed previous 

 observations, but the eggs have been found elsewhere in the 

 flower — especially in the substance of the petals. 



Thrips are very fond of flowers, and almost any flower in 

 the garden yielded specimens of pea-thrips (together with 

 other species) during the period of attack. They seemed, 

 however, to be mere visitors, and no injury appeared to be 

 done except in the case of peas. There are still obscure points 

 in the life history of this pest, especially with regard to its 

 winter quarters. So frail an insect seems ill adapted to 

 withstand the rigours of winter, and though a few examples 

 have been proved to shelter under the loose bark of old pea 

 sticks, these would hardly seem to account for the severity of 

 the summer attack, and as yet we do not know the main 

 source from which the pea attack is derived. The appearance 

 of the injury due to this insect must now be familiar to 

 everyone who grows garden peas, for it is rare to find a 

 crop entirely free. In slight cases the pod is disfigured by 

 whitish patches, for the most part situated near its two ends, 

 but when the attack is severe the pod is much discoloured 

 and distorted, presenting generally a leprous appearance, and 

 sometimes entirely arrested in its development. 



