ee 6 
EXPERIMENTS WITH KEROSENE FOR SCALE-INSECTS. 17 
CRESCENT CITy., FLA., November 28, 1882. 
Sir: Since I last wrote I have been occupied in making drawings, 
and have finished the rust mite and its two enemies (larvee), Syrphus 
fly of orange Aphis—larva, imago, and puparium ; also, sketches and de- 
tails of several other orange insects. I confine myself at present mainly 
to such drawings as need to be made from fresh or living specimens. 
Some biological work is also in progress, and | have tried very hard to 
breed the flies of the rust mite enemy, but so far I have failed to get 
specimens fit for drawing. Experiments made in September with kero- 
sene washes on purple seale (M. citricola) show that the eggs are much 
more difficult to kill than I had supposed. They have not been killed 
by 66 per cent. kerosene and soap emulsions diluted 1 to 9. This scale 
has been somewhat neglected in my last year’s work, and I now find it 
important to get separate results for this scale. We have been having 
cold weather, with several very slight frosts, and I find the action of the 
kerosene very severe upon the foliage when frost or cold weather occurs 
soon after an application. Jn spring or summer the amount of defolia- 
tion depends entirely upon the condition of the trees, but at this season 
atmospheric conditions appear to have a great influence. When the air 
is charged with moisture, and the nights are cold, with frost or heavy 
dews, the oil does not evaporate as rapidly as in warm or dry weather, 
and consequently the effect of an application upon the foliage is much 
more severe. I cannot detect any injurious effect on the bark. When 
defoliated the trees push out new growth almost immediately, and it 
seems to be the general opinion that this is not desirable when there is 
danger of frost. On the whole I am inclined to think it a risk to wash 
trees in winter or late in the fall. If, however, the trees have been neg- 
lected, and are badly infested with scale, it is perhaps preferable to run 
this risk rather than to allow the scales to complete their winter brood. 
I expect to learn much on these points the coming winter, as I think we 
will have one or two frosts before or soon after Christmas. 
I have carefully gone over Dr. Neal’s report, and have a few comments 
to add to my former communication. 
‘Dr. Neal says “the greater the percentage of rosin in the soap the 
better the emulsion I found it made.” This may be true of the emulsion, 
but when diluted, the rosin, or a large part of it, separates from the 
liquid and forms a waxy scum on the surface, which clogs the pump and 
nozzle, and is troublesome unless removed. This scum is insoluble, and, 
if heated, some tree oil separates from it. In murvite I think the balsam 
separates in the same way from the diluted wash. Whale-oil soap, not. 
withstanding the impurities it contains, gives no such scum. 
The strongest emulsion used by Dr. Neal contains 50 per cent. of oil, 
and the strongest wash a dilution of 1 to 9. My experiments with milk 
emulsions of this strength did not in the end prove satisfactory, and I 
long ago decided to increase the amount of oil in the emulsion. I now 
use 66 per cent. emulsions diluted 1 to 9, and these, although sufliciently 
14806 on——2 
