92 
Psyche 
[June-September 
mixed and squeezed into short lengths of paper soda straws. These 
baits have proven to be extremely effective against the fire ant in test 
plots in Alabama, probably because the Kepone takes five to seven 
days to kill, and thus puts off bait shyness until the entire colony has 
fed upon the poison. The USDA has also recently completed some 
bait tests. The effect of these formulations upon wildlife has not yet 
been fully tested, and there may be a hitch in this direction. 
Perhaps even more promising is work done over the last few years 
by E. O. Wilson at Harvard 25 and M. S. Blum; and his associates at 
Louisiana State University 2 with the so-called “trail substance” of 
the fire ant. This material, found in one of the sting glands of the 
ant, is used by the ants to mark trails leading back to the nest from 
food sources or other attractive objects. This liquid is released through 
the sting, which is used like a pen to draw a trail on the ground. The 
odor of the trail substance induces stereotyped foraging behavior, and 
also serves as the marker along which the ants run. Apparently, each 
species of fire ant has its own distinctive trail substance. At' the present 
writing, the chemical composition of the trail substance is not known, 
but like other natural products, it will eventually be worked out, and 
synthesis of its components and related compounds should be possible. 
The trail substance has the advantage that it is a necessary part of the 
ants’ communication system, and it is extremely potent. Presumably, 
it could be used to lead the ants to poison baits, or, more hypothetically, 
it might be used as a “confusion lure,” broadcast in high concentra* 
tions, leading the ants to forage fruitlessly in all directions. 
THE MEDITERRANEAN FRUIT FLY 
Introduction 
The Mediterranean fruit fly (or “medfly,” Ceratitis capitata) and 
other fruit Hies of greatest importance belong to a family (Trypeti- 
dae) of the two-winged or true flies (Diptera): They are not to be 
confused with the fruit flies of genetics, which are primarily yeast- 
feeders of the genus Drosophila, belonging to another family of the 
same order. 
Biology and Nature of Damage Done 
The adult true fruit flies vary from much smaller than a house-fly 
to somewhat larger, and they usually have their wings “pictured” 
with dark markings. In the usual case, the fruit fly female, after 
mating, will puncture unripe fruit and deposit one or more eggs in 
the incision. The larvae are whitish or yellowish maggots that feed in 
the fruit on the branch, and then either drop to the ground, or leave 
the fruit after it drops, and pupate in the soil. Infested fruit is, of 
