-12- 
and 20 parts of sulfonated cantor oil at 9.6 parts per million 
gave a mortality of 100 percent after 72 hours. For the control 
of these midges in the two fresh-water lakes at the tfew York 
World's Fair, derris was used, starting in Aoril 1939. In con- 
junction with each derris application, conrer sulfate was dis- 
solved in the lakes at the rate of 1 part per million in order 
to kill most of the algae therein, which served as a source of 
food and shelter for the larvae and to increase the. potency of 
the derris by reducing the alkalinity of the lake water* Spray- 
'ing was started on : April 10, when the water temperature reached 
50° F. and the overwintering larvae started to show signs *f 
activity. Sufficient derris of 5 percent rotenone content was 
aoplied to "build up a concentration of 6 parts per million (a 
dilution of 0.00003 'percent rotenone) in 77illow Lake and a con- 
centration of 10 parts per million (a dilution of 0.000C5"percent 
rotenone) in Fountain Lake. The results were very striking, parti- 
cularly in Fountain Lake. Many, dead or dying bloodworms ^-ere 
soon observed floating on the water, thousands of others ^ere 
washed ashore, and the lake bottom was covered with the dead and 
deconroosing bodies of the larvae. Thereafter the intery?l be- 
tween treatments was based on the life cycle of the species 
involved. The control operations m ere extremelv effective- against 
Chironomus lobif erus , C. cingulatus- , and the Cj_ tenuicaudatus 
group of small green midges. These had. been the dominant species 
during the summer and fall of 1938. The other Chironomus species 
and the Teny tarsus were also very definitely under control. 
The species present were: Chironominae — Chironomus lobi- 
f erus , C. cingalatus , C. tenuicaudatus , C. so . near tenuicaud- - tus . 
C. brachialis Coo. , _C^_ nervosus , C. sp . near nervosus , C. sp. 
near pa ganus , C. decorus , Tanytarsus eminulus (We Ik.), and 
(Tenypodinae) Frocladius culiciformis (L.), P. choreus (Ueig.), 
and Tanypus puntipennis I'eig. Derris wr s not so toxic to Fro- 
c ladius as. to Chironomus larvae; however, the number of Prc- 
cl^ius adults that emerged was kept down very considerabl-y by 
measures directed against the pupae. The active pupae tended 
to congregate in great numbers in protected places on the lee 
shore of the lakes and could be killed there by spraying with 
derris or with the nyre thrum-kerosene emulsion that was used for 
the control of mosouito breeding. 
C hironomus sp. 
Euchmann (45) in 1932 described tests with finely pondered 
derris oo^'der against larvae. ' Strewed upon n&tef at the rates of 
50, 25, 12, and 6 mg. per liter, it killed ell' within -24 hours. 
A piece of derris ro^t rut in a breeding gl-^ss containing larvae 
killed -them in 6 to 8 hours. An aqueous extract of the root acted 
similarly. 
