- 20 - 
AlDout 2iJ-,000 of thes" bretlos w-'-T"-: used, anr. the.'- ■proved to "be entirely 
suita'ble "becFUse of their ads.pta.Dilitj- to la"boratory conc.iticns. 
Erontispq. lor-gissina G-estro 
These hispids li^j-ing en coconut proved in laTsoratory tests to "be 
readily killed "by derris. Wetting \^ith derris povder pusioensions having 
rotenone content of UIO^OOO to 1:20,000 was effective on "both adults and 
larvae. Control by means, of derris vrould probably be more difficult in 
practice, b'^.-cause the insects liv"- concealed in the unopened leaves. These 
leaves should be opened as far as possible and the derris powder sprayrd or 
dusted into the heart of the cluster.— Van der Vecht (Uoi) in 1936" 
Cassida sp, , a tortoise beetle 
Both adults and _larve.e of a species of Cassida on beets were resifet- 
ant to derris. — Anonymous (2_) in 1937 • 
(Aulacophora ) Ceratia f lavomargin r ta Duviv. 
" '- (401) in 1936 
Freouontly a serious pi^st of cucurbits. Van der Vecht/ report ^--^d 
that the beetles are extraordinarilj^ sensitive to derris. In the labor- 
atory conclusive results vrere obtaine-d by spraying with derris povrder 
in wat'^r, rotenone content 1:2,000, 1^3,000, and 1:5,000. All treated 
beetles (in lots of 20) vrere paralyzed after a short time and werr- de?d 
within 1 to 2 days. 
Also, spra-^ing vrith suspensions with rotenone content of 1:10,000, 
1:20,000, and 1:30,000 was frequently conclusiv?-^. All the beetles were 
paralyzed v;ithin a few hours; however, death usually occurred Inti-r, 
aft-'-r 2 to 6 days, and in case of treatment withi. the 2 last-named linuids, 
1 to 2 of the 20 beetles reacted to contact even after 6 days. All the 
insects vrere paralyzed by spraying vrith suspei-sions with, rotenone content 
of l:Uo,000 and 1:56,000, but at every test 2 of the 20 beetles recovered, 
the other IS dying after 2 to 5 deys. In field spraying test<^. made in 
triplicate on about 50 to 100 beetles each tii^ie, with derris^powder sus- 
pensions in water (rotenone content l:~20,000) 100 percent always died. , 
If more dilute spray liquids were used, a few beetles a^lways remained 
alive. Van der Vecht recommends a suspension v/ith a. rotenone content 
of 1:10,000 to 1:20,000; that is, 1 to 2 gm. per lit^r of a powder with 
about 5-p"'rcent rotcno::e content. 
Dusting with derris pow^'er diluted with talc also preyed efff^-ctive 
against the beetles. The ins'ct-^, were paralyzed within a few hours and all 
died within Zk hours after dusting with powders that contained 0,25 to 0.5 
percent of rotenone. Even by dusting with a mixture of eeual parts of talc 
and a derris povrder containi g less than 0,3 percent of rotenone and only 
6 percent of ether extract, the beetles were still paralyzed; in a few 
instances, however, U or 5 days elarjsed before they died. Dusting with 
talc powder plus 5 percent of ether extract without rotenone vras also effect- 
ive, th-^ treated insects being paralyzed in 1/2 hour and dead in 1? hours. 
Van der Vecht rccom-aends for dusting: High-grade powders to be diluted to 
0.5 percent rotenone content; lovr-grade to 0.25 percent. 
