CONTROL OF ARGENTINE ANT IN ORANGE GROVES. 9 



The purple, 1 red, and yellow scales are the most important ar- 

 mored scales on citrus trees in California, but these usually are con- 

 trolled in this State by hydrocyanic-acid gas fumigation, the results 

 of which are not interfered with by the ants. Judging from present 

 information the ants do not appear to cause excessive infestations of 

 any of these scales in California. 



THE ANT AND THE ORANGE APHIS. 4 



Notwithstanding the fact that the common aphis, or " green louse," 

 infesting orange trees appears to be desired less by the Argentine ant 

 than are the soft scales mentioned, it always is attended directly and 

 stroked by the ant for its honeydew. This aphis, furthermore, should 

 receive quite as much benefit as the armored scales from the mere oc- 

 currence of the ants upon the trees, but it suffers heavily from in- 

 ternal parasites, whereas scales do not. The ants are ineffective 

 against these little parasites, which often may be seen "stinging" 

 and depositing their eggs in aphids, even while attended by the ants. 

 The parasites are very small and active and nimbly avoid the ants. 



The orange aphis becomes abundant on the tender growth in the 

 spring in both Louisiana and California, and often increases during 

 April and May, sometimes causing some of the leaves to curl. It dis- 

 appears rapidly, and numerous dried remains, each with a circular 

 hole through which a parasite has emerged, indicate the effectiveness 

 of these little enemies. The parasites are aided in the destruction 

 of aphids by certain lady-beetles, lacewings, and syrphus-fly larva^, 

 which are more or less immune to the attack of the ants. The para- 

 sites, however, destroy a very large proportion of all the aphids, and 

 very effectively control them in amc-infested as well as all other 

 orange groves of California and Louisiana. The Argentine ant, 

 therefore, does not cause any important loss to the citrus industry 

 through the orange aphis. 



THE ANT AND THE CITRUS WHITE FLY.s 



The Argentine ant does not attend or obtain honeydew from the 

 citrus white fly. It is a direct enemy of this insect, the adults of 

 which it captures in large numbers during the principal emergence 

 periods. The ant sometimes is seen with immature stages of the 

 white fly in its jaws, but these are usually pupae from which the 

 adult insect is almost ready to emerge and which the ant im- 

 patiently has seized. A varying proportion of the emerging white 

 flies are captured by the ants, and in some cases for days at a time 



1 Lepidosaphes Tjeckii (Newm.). 4 Aphis gosypn Glov. 



2 Chrt/somphalus aurantii (Mask.). Dialeurodes citri (Ashm.). 

 * Chrysompfwlus citrinus (Coq.). 



27818 18 Bull. 928 2 



