Pacific island of Rota (11). Small absorbent 
boards containing a combination of methyl- 
eugenol, a powerful lure for the male oriental 
fruit fly, and a potent insecticide, naled (or 
Dibrom ®)), were dropped by airplane every 
few weeks. Responding insects consumed the 
odorous attractant and died by the millions. 
In a matter of months, the males were an- 
nihilated and the species on the island perished. 
Eradication was accomplished at a cost of 
only 50 cents an acre, including distribution. 
You can see the advantages of this approach 
even aside from the low cost. Only the offend- 
ing insect is attacked, Wildlife is not affected, 
Insecticides are not spread needlessly. 
These results indicate that we can look 
forward to the eradication of the oriental 
fruit fly on a larger scale; eventually complete 
eradication of this insect may be possible. 
In 1885, Coquillett attempted to control 
grasshoppers in California with a poisoned 
bait (3). The experiment was a failure, but 
the idea recently has been successful (9). 
With the proper food lure, mych less toxicant 
is required to do a given job than with in- 
secticide alone, and complete coverage is 
not necessary because the insect comes to 
the lure. A clever adaptation of this tech- 
nique has been used against the imported 
fire ant 
Forel). Mirex, a very slow-acting poison, and 
soya bean oil, a food lure, are dispensed on 
a granular carrier (corncob grits). The un- 
suspecting ants carry the granules into the 
colony nest and, as is customary with social 
insects, the food is passed throughout the 
colony. About 2 days later the poison takes 
effect and wipes out the colony. From 96 to 
100 percent control was obtained with less 
than 5 grams of insecticide per acre (12), 
There was no effect on wildlife or fish and 
no contamination of milk or other food prod- 
ucts. Needless to state, many foods and oils 
were evaluated in food acceptance tests be- 
fore soya bean oil was chosen (13). We have 
to seek out these individual preferences, 
because this is what is required to selectively 
eliminate a species from a complex environ- 
ment. 
The food-based attractants supplement the 
powerful specific ones very nicely. The power- 
ful lures help detect the insect; the inex- 
pensive food lures, which do not require 
(Solenopsis saevissima richteri 
36 
specificity or long-range action, cut down on 
the amount of insecticide needed and help in 
control or eradication. 
The instances of success in the attractants 
field have not been easily won. It will not be 
possible to detail the enormous amount of 
technology that had to be built up before any 
of the cited achievements could be accom- 
plished. However, several examples will 
illustrate the point. 
The search for a synthetic medfly attractant 
started with empirical screening of many 
types of compounds and materials. To make 
this operation efficient, a rapid method of 
bioassaying large numbers of candidate mate- 
rials was necessary. 
The screening of attractants is by no means 
as straightforward as the screening of in- 
secticides. The bioassay must be built around 
the idiosyncracies of each species (14). The 
olfactometer that measures attraction for the 
medfly is an 8-foot cubical screened en- 
closure that contains about a dozen chemi- 
cally baited traps on a slowly rotating wheel. 
As in nature, the flies respond to the most 
attractive chemicals while in free flight. 
Testing is further complicated by the effect 
of vapor concentration on attraction. The ideal 
lure will attract at high and low concentra- 
tions, but few chemicals act in this way. 
Instead they become repellent at concentra- 
tions that are too high and are not detectable 
at low concentrations, 
In order to make good progress, a means 
of bioassaying insects the year around is most 
desirable. Laboratory evaluation makes this 
possible and greatly speeds up testing by 
eliminating all but the most promising chemi- 
cals, Field testing is a valid recourse; but 
it is time consuming, costly, and usually 
possible only during a limited part of the 
year. A means of rearing insects is needed 
to supply insects for the bioassay. Even 
when they are available, such rearing may 
be complicated by cannibalism, vulnerability 
to disease and parasites, appropriate diet, 
etc. Daily and seasonal variation, stage or age 
of the insect, as well as normal biological 
variation, all make the testing of attractants 
a far more sophisticated procedure than that 
of testing insecticides. 
Then there is the persistence or attractive 
life of a chemical, the method of exposing it, 
