240 TJie Pea Thrips (Kakothrips robustus) 



or the tip of the pod, but often, when the pod is much curled, the whole 

 of the concave side may be 'silvered' (Fig. 12). The silvering is 

 due to the presence of air in the outer cell layers of the plant let in by 

 the sucking of the larvae. 



The damage can be very extensive and occasionally the whole crop 

 is spoiled. A correspondent at Sevenoaks, Kent, speaks of "several 

 rows hopelessly ruined," while another at Reading had to give up growing 

 beans because of the injury they suffered, but he unfortunately tried 

 peas instead. 



Food Plants. 



The species seems to confine itself chiefly to the edible pea [Pisum 

 sativum) and the broad bean {Vicia faber) and their varieties. Both 

 field and garden crops may be attacked, but the latter seem to suffer 

 more frequently. This may be due to the fact that in fields there is 

 usually a rotation of crops, while in gardens the same crop is often 

 grown on the same plot or quite close by year after year. I have not 

 yet found this species on either sweet peas {Lathyrus odorafus) or 

 scarlet runner beans {Phaseolus vulgaris), though Gaumont and 

 Vuillet (1914) mention these as host plants in France. Thrips are 

 often abundant on both plants, especially the latter, but, in my experi- 

 ence, always other species (chiefly Frankliniella intonsa, Thrips tabaci, 

 Thrips valida, Physothrips atrata), and I am inclined to think that 

 when damage is recorded on runner beans that it is due to one or more 

 of these species and not to Frankliniella robusta. 



I have also found this species on flowers of knapweed {Centaurea 

 nigra) and both Uzel (1895) and Bagnall (1908) have taken it in flowers 

 of Scabiosa arvense. Gaumont and Vuillet (1914) mention also Medi- 

 cago saliva, Cijuga reptans, Ecbaliiim elalerium and Coronilla vulgaris; 

 the two last do not occur in Britain. 



Other Species found on Peas and Beans. 



Aeolothripidae {Antennae ^-segmented). 



Aeolothrips fasciatus. Common; easily recognised by its large size 

 and banded black and white wings. Partly carnivorous, but also feeds 

 on pollen and plant juice. 



Melanothrips fuscus. Occasional ; recognised by its large size and 

 smoky black wings with very distinct veins. 



