186 



EEPORT UPON COTTON INSECTS. 



collection of the American Entomological Society, Academy of Natural Sciences, Phila- 

 delphia, are identical with the specimens sent. 

 Worker. Length, -J- inch. 



Color. Abdomen, tip of scale and cone, femur, tibia, vertex, and f agellum, black or 

 blackish. The face (except vertex), scape, tarsus, thorax, brown or brownish. There 

 is no tuft of hair beneath the fa ce. They were found by Mr. Coinstock actually destroy 

 ing the cotton-worm. 



D. insanus was collected by me in Texas (1877), and a variety quite akin to it in Col- 

 orado, 1879. In the former State, in the neighborhood of Austin, it was found near or 



on the flat circular disks of the agri- 

 cultural ant, Pogonomyrmex barbatus. 

 In Colorado the nests were found in 

 great numbers in the Garden of the 

 gods and vicinity, upon the clear 

 space surrounding the gravel-covered 

 mounds of Pogonomyrmex occidenlalis, 

 Cresson, which, like its Texas con- 

 gener, is a harvesting species. Two, 

 three, and four of the former nests or 

 openings would be placed upon the 

 latter. The external architecture of 

 D. insanus is simply a moundlet of 

 sand, two to four inches in diameter, 

 gathered around a small opening into 

 the ground like the familiar nests of 

 Lasius flavus, the little yellow ant 

 which burrows in such multitudea 

 in our garden walks and lawns. 



In action the erratic ant is vigorous 

 and active. It is remarkably cour- 

 FlG. 35. Dorymynnex insanus. ageous, and was often observed by me 



to attack successfully the Occidental ant. In one case a small colony of erratics pushed 

 up its gate in the midst of one of the principal thoroughfares of a large occidental formi- 

 cary. Thereafter the little erratics flung themselves upon nearly every occidental that 

 passed with such vigor and abandon of courage as to finally compel the latter, though 

 greatly superior in size and armed with a formidable sting, to give up the gangway, and 

 excavate an opening beyond the erratic boundaries. One remarkable example of this 

 especially attracted my attention. Upon the circumjacent clearing of an occidental nest 

 which was being opened for the study of internal architecture, there were three nests or 

 gate- ways of an erratic colony. My invasion of the formicary had, as is usual, aroused 

 the occidentals to the highest pitch of belligerent fury. They attacked me with so 

 many and painful stings as quite to sicken me. Yet the erratics freely assaulted these 

 irate insects as they ran hither and thither whenever they trespassed upon their bor- 

 ders, and invariably drove them away. If such intrepid little warriors were to devote 

 their atttention to killing cotton-worms they would doubtless do good execution. 



The genus and probably this species is widely spread throughout tropical and sub- 

 tropical America. It feeds upon the sweet exudations of plants, galls, and sweet excre- 

 tions of the Aphis ; but, like most ants, is fond of the juices of insects. 



No. 2. D. flavus, n. var. 



Worker. Length, inch. 



This variety is identical with insanus, except in the color, which is a uniform honey- 

 yellow, and the contour of the thorax. The apex of the abdomen and the flagellum 

 of the antennae are tipped with a blackish hue. The variety appears to be quite per- 

 manent, the distinction holding in a number (25 or 30) of specimens examined. The 

 cone is evidently higher than the thorax. There is no tuft under the face. 



Habitat, United States. Southern States. 



