44 Indian Museum Notes. [Vol. VI. 



In May at Peberenda, Dalsingsarai, I found the indigo in the 

 neighbourhood to be seriously damaged by these pests. I was in- 

 formed that the plants had been attacked by these insects ever since 

 the 2-leaf stage. There is but little doubt that when the plant is 

 in its 9- or 7-Ieaf stage the aphid causes the death of many of the 

 plants. I almost invariably found that plants free from thrips and 

 aphid were comparatively robust and healthy, while these insects 

 occurred in numbers on stunted indigo plants. I should estimate 

 that on an average healthy and unaffected plants were from four to six 

 times taller than infested plants. 



Taking these pests in detail. — 



The Indigo aphid. 



The Indigo aphid is an insect belonging to the family Aphidae 

 (plant lice) of the order Hemiptera or bugs. It can be immediately 

 distinguished in the winged state from the indigo psyllid (Psylla 

 isistis, Buckton) by the venation of the wings. As a matter of fact 

 winged specimens of Psylla isistis have never been found. The 

 venation, however, will agree in general characters with the psyllid 

 type, but I am not certain, until the winged adult is discovered} 

 under what sub-family of the Psyllidse, Psylla tststis will fall. The 

 wingless specimens can be distinguished by their globular bodies, 

 the body of Psylla isistis being flattish in the larval and pupa 

 stages. Fhe aphids vary from light green to brown in colour. The 

 winged specimens are dark brown. The wings are transparent and 

 the veins show as browr lines. (See Plate IV, fig. 12, 12 a, 12 b.) 



These insects cluster in large numbers upon the indigo stems, 

 terminal shoots and leaves. So thickly are they crowded together 

 that it is usually impossible to see the stem itself. In May, though 

 the greater number of the aphids were wingless, winged ones were 

 present. I am unable to say how many generations the aphid 

 passes through from the time the indigo appears above ground to 

 the commencement of the rains, but it is probably several. As how- 

 ever, weather conditions, climate and the like, have great influence on 

 the number of generations, there is little value in working the 

 matter up beyond discovering the average number of generations in 

 this period. It is important, however, to discover its alternative 

 food plant or plants if any. In my opinion this insect does a great 

 deal of harm, especially in those years when rainfall is late and 

 scanty as the plant is unable to recuperate from the attack of the 

 aphids. This damage I should estimate can run up for the first 

 mahai to as far as 4 or 6 annas of the crop, and in some cases 

 possibly more. All the plants I examined, which were very 



