42 
EXPERIMENTS WITH PYRETHRUM. 
Simple aqueous decoctions, as reported in Bulletin 24 (pp. 39-44), 
having proven a signal failure, it was thought advisable to experiment 
with some of the oils as agents for drawing out the insecticidal element. 
Headlight oil was selected, for the reason that the quality obtained from 
country dealers is much more constant and reliable and hence bet- 
ter for a series of experiments. Comparative tests of the power of ex- 
traction of the oil by various methods were made, as also of the oil 
combined in an emulsion with other than oil extracts. Asa check upon 
the pyrethrum emulsions the simple oil emulsion was used in several ex- 
periments, in order that the effect of the oil in the combination might 
be known and any additional advantage of the second factor rendered 
capable of more definite determination. 
Simple Emulsion. 
Method of preparation. — Oil 2 parts, water 1 part, and enough soap to emulsify 
well. Water heated and oil added while the water boiled. Churned until the mixture 
thickened. Prepared October8, and is yet in perfect condition November 10. Used 
in experiments 1, 2, 3, aud 4. 
As Boll Worms were scarce, the larvae of the Cotton Worm (Jletia xylina) were 
used in all pyrethrum experiments. 
Experiment 1. 
October 10 {12:35). — A 4 per cent water dilution was made and sprayed upon larvae 
on cotton plants in the held. The larva, seventeen in number, were taken from the 
sprayed plants and placed upon fresh unsprayed leaves in a box, later being placed 
upon fresh food in breeding cages. This method was followed in all subsequent ex- 
periments. The sprayed branches in the field were always appropriately marked, in 
order that the effect of the emulsions upon the foliage might be noted at any time. 
Date. 
Living. 
Dead. 
October 12 
Total 
2 half grown. 
Hi grown 
15 
2 
Experiment 2. 
October 10 (12:30). — A 6 per cent dilution was sprayed upon 32 larvas. At 5 p. m. 
it was noticeable that the younger worms were somewhat affected, but the larger 
ones showed no uneasiness. 
Date. 
Living. 
Dead. 
October 12 
Total 
2 half grown. 
lu very young. 
20 
12 
