22 SECOND REPORT ON ECONOMIC BIOLOGY. 



On examining this box on July i5th quite half of the specimens 

 were still alive and active. The dead specimens were taken out, and 

 the living ones allowed to remain. Examined again on July i8th 

 seventy were still alive. Further examinations on the 2oth resulted 

 in finding twenty alive, on the 22nd twelve, on the 24th ten, and seven 

 on the 25th, three of which died on the 26th, having existed for 

 practically three weeks without any food and in a temperature of 

 nearly 105 F., being on a bench in the window which received the 

 full sunlight from 9 a.m. to 6 p.m. 



Whether the larvae of other species are capable of existing for 

 so long a period without food I cannot say, but the fact that an 

 appreciable percentage of the original two hundred existed for a fort- 

 night suggests great possibilities in the way of distribution of this 

 insect. 



The results obtained may be summarised as follows : 



i. On smooth white paper or glass surface the larva travelled 

 nearly 8 feet in a period of two hours in a temperature between 

 780-84 F. 



2. On a teak boarded surface in the same length of time, at a 

 slightly higher temperature, the rate of progress was just over four 

 feet in two hours. 



3. In all cases the insects travelled in the direction of the light, 

 and when placed in semi-darkness, they made their way towards the 

 light. 



4. The larvae continued to live in a temperature of up to 105 F., 

 but higher than that the rate of mortality was great. 



5. Three larvae lived in a temperature of 105, without any food, 

 for a period of 20 days. 



THE DUSKY=VEINED WALNUT APHIS. 



Ptychodes juglandis, Frisch. 



This insect made its appearance on walnut trees in Huntingdon- 

 shire in July last in enormous numbers, and occasioned considerable 

 damage. After the aphids had been on the trees a short time, the 

 leaves became blotchy and almost yellow, later assuming a scorched 



