Ll. Lloyd 19 



contains relatively larger quantities of phenols. The effect of these varies 

 greatly, but in the proportions in which it is safe to use them they are 

 toxic only to the adults and this makes them unsatisfactory and ex- 

 cessively costly owing to the necessity for repeated applications. 



From 50 to 200 adult white flies on foliage were placed in half-gallon 

 glass-stoppered jars and small quantities of pure naphthalene, cresylic 

 acid and phenol, alone and in various combinations, mixed with ash were 

 introduced on watch glasses. Notes were made of the rate at which the 

 insects were stupified and after an hour the fumigants were removed and 

 the jars were left with muslin covers. A count of the mortality was made 

 the day after the fumigation. The results of a small series of fumigations 

 are given in Table IV. It will be seen that the mortality was slight 

 where naphthalene alone was used, heavy with cresylic acid or phenol, 

 but almost total in most cases (10 out of 12) when naphthalene was used 

 in combination with the tarry acids. The rate of stupifaction was in the 

 same proportion as the final mortality, being slow when naphthalene 

 alone was used. A similar series was carried out with various grades of 

 naphthalene, 0-25 grm. in 0-75 grm. of ash being used and the fumigation 

 lasting 70 minutes at a temperature of 66° F. The mortality was as 

 follows : 



1. Naphthalene, pure flake killed 4/65= C-1 % 



2. „ high grade white (Crow & Co. ) .. 1/57= 1-7 



3. „ ci-ude (carbon impurities) ., 1/35= 2*9 



4. „ „ (another sample) „ 2/60= 3-3 



5. „ drained salts (Crow & Co.) „ 50/62=80-7 



6. 1 grm. containing 75 % destructor refuse and 



25 % volatilisable naphthalene containing 



some tarry acids (proprietary remedy) ,, 15/89 = 16-8 



Table IV. SJiowing the 'percentage mortality of adult A. vaporariorum 

 obtained in vitro wiih pure naphthalene alone and with tarry acids, 

 fumigations lasting one hour. Temperature 69-72° F, 



Naphthalene grms. 



, A 



0-1 0-2 0-3 0-4 0-5 



No tarry acids — — — — — 3-5 



— — ——— 30 



Cre.sylic acid ("pale straw") 0-1 grm. 79 — — — 62-6 95 



64 — — — — — 



Pure phenol 0-1 grm 66 100 99 99 98 97 



39 — — — 100 98 



76 — — — — — 



Cresylic acid 0-1 grm. + phenol 0-1 grm. 78 — — 85 — 100 



75 — — — — 100 



2—2 



