90 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



ants occupied in destroying the eggs of Aletia, or still more frequently 

 in attacking the young worms that are helpless while in the act of molt- 

 ing, or in devouring the interior of the still more helpless chrysalides. 

 Even old worms which, from cause whatsoever, once get to the ground, 

 are almost sure to fall a prey to these persistent and voracious little 

 animals; the writhings, jerkings, and jumpings of the worm being of 

 no avail against the constantly increasing numbers of the enemy that 

 come to the attack. Attractive as is the honey from the glands of the 

 cotton plant to the Cotton Moth, it seems to attract few other insects, and 

 even the ants, that have such a predilection for sweets, are only oc- 

 casionally found partaking of it. The universal presence of ants on the 

 cotton plants, and of their nests in the ground at the base of the plants, 

 seems largely due to the similarly universal presence of the cotton plant- 

 lice. 



The ants are always to be seen busily occupied in obtaining sweets 

 from these Aphides, while but few are noticed to be sucking the liquid 

 secreted by the glands. Now the plant-lice rapidly decrease in number 

 with the advance of hot weather, though they never disappear entirely 

 from the plants. The ants, as summer advances, are thus deprived of 

 a large portion of their principal food supply, and as their colonies be- 

 come more and more numerous with the progress of the season, they 

 are obliged to seek other food. It is but natural, therefore, that they 

 should fall to preying on the Cotton Worm. It has already been men- 

 tioned that rains hinder the working of the ants, and that storms 

 destroy them. They will, therefore, prove most effectual in assisting 

 man where they are most protected from heavy showers, as on new 

 land where the soil is uneven, or in fields where there arei' stumps, 

 trees, &c. 



To Mr. Trelease the work of the ants seemed so important as to sug- 

 gest the possibility that the nectar glands of the cotton plants were 

 originally developed by natural selection for the purpose of attracting 

 ants which should act as protectors against the attacks of Aletia or 

 some other enemy. 



The species actually observed destroying the cotton worm have either 

 been determined or described by Eev. H. C. McCook, and are as follows : 

 Dorymyrmex insanus (Buckley), i>. flavus McCook (variety of insanus), 

 Iridomyrmex maccooMy Solenopsis xyloni McCook (=S,geminata'Fahr,), 

 and Monomorium carbonarium Smith. In addition to these, Cremasto- 

 {/aster lineolata Say and Q, clara Mayr are found nesting in the cotton 

 fields and may be safely counted among the enemies. For descriptions 

 of these species see note ^. 



The most common and effective species in the Southwest is the Sole- 

 nopsis geminata Fabr., a small species (Fig. 10) averaging 2.8™™ in length, 

 and of a pale fuscous color, with a darker, piceous abdomen. 



Among the DorylidsB (a family closely related to the ants and consid- 

 ered by some as belonging to them) we have found Labidus harrisii 



