380 Insects and Potato Foliage 



5. June 12. Put one clean plant under cloche with one striped nymph Off grass. 

 June 13. No visible result. 



6. June 14. Put one clean plant under cloche with three Capsids collected 

 at Wisley. 



June 15. No visible result. 



June 17. Youngest leaves with brown blotches. 



7. June 14. Put one clean plant under cloche with nine Capsids collected at 

 Oxshott. 



June 15. Small brown spots appeared on the youngest leaves. 

 June 17. Attack severe. All the youngest leaves spotted and blotched and 

 nearly dead. Six Capsids were observed. 



8. June 14. Put one clean plant under cloche with one Capsid collected at 

 Oxshott. 



June 17. No visible result. 



Capsid series. (B) Chelsea. 



1. June 11. Put three clean plants under a bell- jar with one green winged 

 Capsid and one green nymph in the last stage, both collected at Wisley that day. 



June 13. No visible result. Added two green nymphs from Walton. 

 June 20. One plant has the small fohage with holes edged with brown. Another 

 plant has two leaves the same. The third plant shows nothing. 



2. June 11. Put two clean plants under a beU-jar with ten luiwinged green 

 Capsid nymphs, collected that day on potato plants at Wisley. 



June 13. No visible results. One winged form, the rest nymphs. 



June 20. The small leading shoots are brown and dead. The smaller leaves 

 have holes edged with brown. 



No control shows these symptoms at all; apparently the Capsids feed on the 

 shoots and youngest leaves and give rise to holes in the leaves and to the death and 

 browning of the apical shoots. This effect has not occurred on any plant at Chelsea 

 except those infested with Capsids. (The action of Eupteryx on the leaves is exactly 

 the same as that at Wisley.) 



Capsid symptoms. 



In these experiments the insects attacked the youngest leaves and 

 small irregular spots or blotches were formed which were either scattered 

 or so numerous as to give the leaf or leaflet a brownish appearance. 

 Each spot when first formed possesses a clear centre with a brownish 

 boundary. The spots are due to the laceration and destruction of the 

 tissue at the places where the insects feed — either on the upper or lower 

 surface (usually the latter) of the leaf. Small pits are formed which often 

 extend to the opposite epidermis and the leaf may be perforated or if 

 not, perforation soon takes place. The dark boundary to the spot is 

 evidently due to the discoloration of the broken cells which form the 

 wall of the pit. Veins near the pit are lacerated, discoloured and some- 

 times severed. When the attack is severe, the chief veins of the young 



