August, ’24] 
DE ONG AND WHITE: DERRIS AS AN INSECTICIDE 
499 
Table 2. San Jose Scale—Parasitism 
Place collected 
Emerged at 
Sligo, Md. 
Number 
of twigs 
Ave. length 
of twigs 
in inches 
Number 
of 
scales 
Number 
of 
parasites 
Per cent 
of 
parasitism 
Fort Valley, Ga. 
Sept. 1922 
11 
4.60 
7446 
0 
0.00 
Aurora, Ill. 
Sept. 1922 
5 
6.05 
3217 
41 
1.27 
Unknown 
Sept. 1922 
6 
6.62 
12028 
0 
0.00 
San Pierre, Ind. 
Nov. 1922 
1 
6.50 
1456 
1 
0.07 
Lafayette, Ind. 
Sept. 1922 
5 
6.40 
9249 
556 
6.01 
Bicknell, Ind. (1) 
Sept. 1922 
22 
4.81 
15790 
90 
0.57 
Bicknell, Ind. (2) 
Sept. 1922 
11 
5.41 
10436 
24 
0.23 
Washington, Ind. 
Sept. 1922 
5 
6.33 
4614 
14 
0.30 
Bentonville, Ark. 
Sept. 1922 
19 
4.35 
25108 
471 
1.88 
Geneva, N. Y. 
Sept. 1922 
12 
6.07 
3077 
52 
1.69 
Oyster Shell Scale—Parasitism 
Aurora, Ill. Sept. 1922 37 2.87 4591 99 2.16 
An examination of Table 2 will show the per cent of parasitism as 
based on these samples to vary from 0.00 for the scales from Fort 
Valley, Ga., and an unknown locality to 6.01 for the scales from Lafay¬ 
ette, Ind. 
FURTHER STUDIES OF DERRIS AS AN INSECTICIDE 
By E. R. de Ong and L. T. W. White, University of California. 
Extracts of Derris have been commonly reported as a valuable in¬ 
secticide, the species when mentioned usually being D. elliptica (com¬ 
mon name “Tuba”), the “derris” of commerce. There are forty or 
more species of this genus, at least twelve of which are found in the 
Philippine Islands. Insecticidal tests have been made with the follow¬ 
ing species by Mr. H. E. Woodworth, formerly of the College of Agri¬ 
culture, University of the Philippines, Los Banos, to whom I am in¬ 
debted for the following data, on species abundant in the Phillippine 
Islands. 
Scientific Name 
Parts Used 
Dilution 
of Solution 
Remarks 
Derris elliptica 
stem 
20% 
negative 
young shoot 
20% 
negative 
root 
20% 
positive 
Derris philippinensis 
leaves 
20% 
negative 
stem 
1% 
positive 
stem (boiled) 
20% 
negative 
roots 
20% 
positive 
