'202 



[Aug. 



Tlie chief question remaining to be disposed of relates to the female. The 

 thorax of the soldiers presents no observable alar cicatrices, and as they arc 

 •anomalous in their small size when compared with the male Dorylus, we must 

 search for the normal female in some large unrecognized form. 



The specimens named rubella, although distinct from arceiix, resemble it very 

 closely, even to the details of the oral organs. The form of the labium, as de- 

 termined by a careful dissection, does not agree with Mr. Westwood's figure. 

 His representation of the maxilinc (in which he has omitted the mando and galea) 

 is more accurate. Both species have a posterior lateral spine on the tliorax, and 

 a compressed sharp spine directed backwards and placed beneath along the middle 

 of the abdominal peduncle, which has also a small lateral tubercle. In rubella 

 the sternum is carinated, and has a spine upon each side of the carina, between 

 the medial co.xas. The head is rather less contracted posteriorly than in arcetis. 

 The general similarity is sufficiently great to make the two species congeneric ; 

 *ind if Dorylus nigricans is taken as the male of rubella, it will be difficult to 

 assign a male to arcoisjTom among the described species of Dorylus. The ab- 

 dominal peduncle of arcetis is slightly smaller than in rubella, whilst the insect 

 is rather larger, so that a Dorylus with a small peduncle may be the correspond- 

 ing male ; and among these D. glabratus S/d-. might be chosen, as it is larger 

 than nigricans. There is, however, too much discrepancy in the color to admit 

 such a conclusion without hesitation, arcetis being black. We are, therefore, 

 inclined to regard Dorylus arcens as a black species with a large peduncle, yet 

 to be discovered as a male. The last character is possessed by D. planiccps 

 Ilald. which, although taken at Cape Palmas by Dr. Savage, is too small to cor- 

 respond with arcens, and its color is lighter than in nigricans. 



Dr. Goheen brought specimens oi rubella from Monrovia, a locality 1500 miles 

 distant from that specified by Dr. Savage. 



Explanation of the figures. 

 Fig. 1, 2, head of Dorylus nigricans, the latter having the mandibles iciuoved 

 to show the absence of the mouth : 3, half of the head of a soldier : 1, mandible ol a 

 worker: 5, maxilla, and 6, half the labium, from a soldier of r«ie//a; all magnified. 



