528 J our7ial of Agricultural Research voi. x, no. 10 



(3) Quassia and quassiin spray solutions, not containing soap, kill 

 aphids when applied sufficiently strong. By the process of elimination 

 it is concluded that death occurs as a result of some of the fine spray 

 being breathed into the respiratory system while the aphids are being 

 sprayed. 



(4) The greater effectiveness of solutions containing soap is due to the 

 weaker surface tension of such solutions, which pass freely through the 

 spiracles and finally reach the nervous tissue, where they kill by slowly 

 aflfecting the nerve cells. 



(5) While nicotine acts quickly and causes pronounced symptoms, 

 quassiin acts very slowly and causes but few symptoms, and these are 

 never pronounced. While nicotine kills by paralysis, quassiin causes no 

 noticeable paralysis, but aphids poisoned by it slowly become inactive 

 and finally die in what is known as "coma" in the higher animals. 



In conclusion, it should be stated that owing to the poor insecticidal 

 properties of quassiin, quassia extract can never become a general 

 insecticide for all aphids. Of course, the amount of extract to be used 

 could be sufficiently increased so that the spray solution would perhaps 

 be efficient on any particular aphid, but in most cases the expense would 

 prohibit its use. The most effective formula (6B, first extract, Table IX) 

 used by the writers was prepared by soaking 22 pounds of quassia chips 

 in 100 gallons of fish-oil-soap solution (1.6 pounds of soap to 100 gallons 

 of water) for 24 hours. This spray solution under the most favorable 

 conditions was efficient on only two of the six species of aphids tested, 

 but the results as recorded are comparable to those obtained by using 

 nicotine-sulphate solution. Nevertheless, owing to the slow action of 

 quassiin, this spray solution is much less reliable than is nicotine-sul- 

 phate solution, because the aphids sprayed have better opportunities to 

 migrate, and should it rain a few hours after the solution has been applied 

 its effectiveness would be greatly reduced, while such is not true for nico- 

 tine-sulphate solution. This spray solution, not including the cost of pre- 

 paring it, is almost as expensive as nicotine sulphate solution (1:800 of 

 soap solution). Formula 3 A (Table IX), the one recommended against 

 the hop aphis, was found efficient on only the nasturtium aphis, although 

 it was sprayed upon six other species. 



LITERATURE CITED 

 (i) Alwood, W. B. 



1889. REPORT ON EXPERIMENTS waTH REMEDIES AGAINST THE HOPLOUSE. In 

 U. S. Comr. Agr. Rpt. 1888, p. 102-iu. 

 Page 105: Quassia. 



(2) BoucART, Emmanuel. 



1913. INSECTICIDES, FUNGICIDES, AND WEEDKILLERS. [Trans, from the French 

 . , , by Donald Grant.] 431 p., 12 fig. London. 

 Pages 328, 375-377: Quassia. 



(3) Brands, W. T. 



1825. a MANUAL OF PHARMACY. 556 p. London. 

 Pages 145-146: Quassia; Lignum. 



