22 
BULLETIN 647, U. S. DEPARTMENT OF AGRICULTURE. 
known or suspected enemies, while the activities of the ants were 
observed on the unprotected tree. The results are summarized in 
Table II. 
Table II. — Influence of the Argentine ant on abundance of mealybugs on orange. 
Louisiana, 191 
Date. 
Ants present. 
Number 
of sound 
mealy- 
bugs on 
tree. 
Number 
of para- 
sitized 
mealy- 
bugs. 
Number 
and kind 
of mealy- 
bug ene- 
mies on 
tree. 
Ants excluded. 
Number 
of sound 
mealy- 
bugs on 
tree. 
Number 
of para- 
sitized 
mealy- 
bugs on 
tree. 
Number 
and kind 
of mealy- 
bug ene- 
mies on 
tree. 
May 7. . 
May 13. 
May 21. 
June 3.. 
June 12. 
July 29. 
Aug. 15. 
593 
234 

110(31.9 
per cent). 
3 (1.3 per 
cent). 
IT. 
2T. 
4D,3T, 
1L.1S, 
1C 

IP 


1,126 
859 
209 (19.5 
percent). 
90(11 per 
cent). 
IT. 
4 T, 3 L 
3 L, 1 C, 
IS. 
2D,1 L. 
0. 
0. 
0. 
Symbols: T=tubuliferan thrips; L= 
the dipteron Leucopis griseola Fallen. 
Paraleptomastiz abrwrmis Gir. 
larva of the pyralid moth Laetilia coccidivora Comst.; D=larvse of 
C=coccinellids; S=Syrphus fly larv«e; P=the mealybug parasite 
At the time of beginning the experiment, May 7, there were 593 
mealybugs on the ant-invaded and 1,126 on the ant-free trees. The 
mealybugs gradually disappeared from both trees, as shown in Table 
II, until by June 12 there were practically none. There was consid- 
erable parasitization and the continuous presence in the mealybug 
groups of several different predacious enemies. On May 13, for ex- 
ample, 31.9 per cent of the mealybugs on the ant-invaded tree were 
found to be parasitized, and 19.5 per cent of those on the protected 
tree also were parasitized. On May 21 the percentage of parasitism 
among the ant-attended mealybugs was 1.3 per cent, whereas among 
those on the protected tree it was 11 per cent. Predatory enemies 
occurred among or near the mealybugs on both trees as long as the 
mealybugs lasted. The more common ones were predacious thrips, 
coccid-feeding larvae of the moth Laetilia coccidivora Comst. (identi- 
fied by Dr. Harrison G. Dyar), and the two-winged fly Leucopis 
griseola Fallen (identified by Mr. Frederick Knab), unidentified 
lady-beetles, and larvae of syrphus flies. At least one parasite, 
Paraleptomastix abrwrmis Gir. (identified by Mr. A. A. Girault), was 
found on one of the leaves of the ant-infested tree. There was no 
evidence that the mealybugs were being attacked by fungus or other 
disease. 
The slightly greater persistence of the mealybugs on the ant- 
frequented tree has little practical significance and in part was ac- 
counted for by the following circumstance: On June 12 a strip of 
