242 The Pea Thrips (Kakothrips robustus) 



found the ladybird larvae in the infested flowers, and believe that they 

 exert little, if any, controlling influence. 



Chalcidae. Vuillet (1914. ii) has recently described a Chalcid Thrip- 

 octenus brut n.sp., belonging to the Tetrastichinae, which he found 

 among the larva of the pea thrips at Darcy, Aisne, France, in July 1913. 

 Although he has not actually bred this Chalcid from the larvae, yet 

 there is little doubt that it does parasitise them as it was always found 

 in conjunction with them, and further the only other known species 

 of this genus {T. russelli) is parasitic on Heliothrips fasciatus, a species 

 which, as mentioned above, is injurious to beans in the United States. 



Thripoctenus russelli, or a closely related species, has been taken in 

 England by Bagnall (1914), but I have found no species of this genus 

 as yet among the pea thrips in this country. I have,, however, found 

 on several occasions in different localities Chalcids among larvae of the 

 pea thrips, but cannot be certain whether they have any connection 

 with these or not. M. Vuillet has kindly offered to let me have some 

 living specimens of his species if he finds it in sufficient numbers, 

 and an attempt will be made to establish it here. 



Other controlling Factors. 



Weather. Wet weather always causes great mortality among thrips 

 and also causes the plants to grow more rapidly. In this species, un- 

 fortunately, the rain has less effect than usual owing to the sheltered 

 position of the insect in the flowers. However, several correspondents 

 mention that the attack is greatest in dry weather and is lessened by 

 a heavy shower of rain. 



Soil. The pea thrips is most prevalent on light soils. In the 

 majority of cases reported to me the soil has been light or gravelly, and 

 a correspondent at Shoreham, Kent, states that the damage is always 

 worse in the village where the soil is light than at Highfield near by where 

 the soil is heavier. It is probable that the conditions in a light soil 

 are more suitable for the hibernating larvae. 



Varieties avd time of planting. No variety of pea or bean is immune 

 to the attack, but the earlier sown plants usually escape severe damage. 

 As the females lay their eggs chiefly in the stamen-sheath of the flowers, 

 any plants which have passed the flowering stage before the adults 

 become common escape almost entirely. Actual varieties of pea 

 mentioned as having suffered less severely in infested districts are 

 'Gradus' (an early variety), 'Primus,' and 'Autocrat,' but a careful 

 examination of nearly forty varieties at a seed testing ground at Withani, 



