958 AN INTRODUCTION TO ENTOMOLOGY 



their wards, which is known as trophallaxis, is discussed in the 

 chapter on Isoptera (pp. 279-280). 



The study of the habits of ants in the field is often supplemented 

 by observations on colonies kept in artificial nests. Several types cf 

 such nests are in use; for descriptions of them see Wheeler ('10). 



The family Formicidae includes seven subfamilies, all of which are 

 represented in the United States; but two of these subfamilies, the 

 Cerapachyinae and the Pseudomyrminae, are confined to tropical and 

 subtropical regions and their range extends only into the southern 

 part of our territory, where they are represented by only a very small 

 number of species. The workers of the other subfamilies can be 

 separated by the following table, which is based on one published by 

 Professor Wheeler in "The Hymenoptera or Wasp-like Insects of 

 Connecticut" (Vierick '16). This work includes also tables of the 

 genera and subgenera of ants found in America north of Mexico. 

 For keys to the subfamilies, genera, and subgenera of the world see 

 Wheeler ('22). 



KEY TO THE SUBFAMILIES OF ANTS 



(Includes only the workers) 



A. Anal orifice round, terminal, surrounded by a fringe of hairs; abdominal 

 pedicel consisting of a single segment; no constriction between the first and 

 second segments of the gaster; pupae rarely naked, most frequently in a co- 

 coon, p. 963 FORMICIN^ 



AA. Anal orifice ventral, in the shape of a slit; pedicel of the abdomen con- 

 sisting of one or two segments. 



B. Pedicel of the abdomen consisting of a single segment; no constriction 

 between the first and second segments of the gaster; sting vestigial; pupas 



naked, p. 962 Dolichoderin/e 



BB. Pedicel of the abdomen consisting of one or two segments, when only of 

 one, a distinct constriction between the first and second segments of the 

 gaster, sting developed, sometimes very small but capable, nevertheless, of 

 being exserted from the abdomen. 



C. Pedicel of the abdomen consisting of a single segment; gaster with a 

 distinct constriction between its first and second segments; frontal carinae 

 separated or close together, when close together, dilated to form oblique or 

 horizontal laminge partly covering the insertions of the antennae; pupae 



always enclosed in cocoons, p. 959 Cerap.\chyin.« and Ponerin^ 



CC. Abdominal pedicel consisting of two segments; pupae naked. 



D. Frontal carinae very close together, almost vertical, not at all covering 

 insertions of antennae; eyes always very small or absent; tropical and 



subtropical, p. 958 Dorylin^ 



DD. Frontal carinae of a different conformation and covering the antennal 

 insertions; eyes rarely vestigial or absent; cosmopolitan, p. 959, 960 

 PsEUDOMYRMiN^ and Myrmicin^ 



Subfamily DOHYLIN^ 



The Legionary or Visiting Ants 



The members of this subfamily are largely confined to Equatorial 

 Africa and tropical America. The colonies are nomadic, wandering 

 from place to place in search of prey, and forming only temporary 

 nests. Some of the species travel in vast armies and often overrun 



