INTRODUCTION. 



The tribe Heterogyna^ suborder x1culea.ta of the Hymenoptera, 

 consists of but one family, the Formicida' or Ants. 



Morphologically ants are at once distinguished from other 

 aculeate Hymenoptera by a remarkable modification of the one or 

 two segments of the abdomen immediately following the median 

 segment or propodeum. This modification of the anterior portion 

 of the abdomen consists in the almost complete detachment of 

 one or two segments from the rest of the abdomen to form a 

 highly flexible pedicel composed of one or two nodes. In the 

 majority of the genera of the Formicidce, the attachment of 

 the pedicel to the median segment in front and to the rest 

 of the abdomen behind is extremely constricted and narrow, 

 giving great freedom of movement to both thorax and abdomen 

 properly so called. When the pedicel is formed of two segments 

 a similar constriction lies between the two. In certain low 

 forms {Myojjopone, Amhlyopone, &c.) the node of the pedicel is 

 attached by the whole of its posterior face to the succeeding 

 segment of the abdomen, showing an approximation to the stiffer 

 and more ponderous form of abdomen possessed by the fossorial 

 wasps of the family ScolUdit'. 



Ants, like the honey-bees and one section of the wasps, are 

 social insects with, in any well-established nest or community, 

 three distinct forms — the perfect and fertile female ( $ ), the 

 male ( c? ), and the so-called neuter or worker ( ^ ), which is 

 merely an undeveloped female. Very often there is more than 

 one form of woi'ker, and in some cases the largest form or forms 

 difl^er considerably from the smaller in structure ; these are known 

 as soldiers {%)■ 



Unlike the neuters among the bees and wasps, the neuter ants 

 are invariably wingless, and generally have the thorax more or less 

 modified and different from the thorax in the female or male. 

 Exceptional cases, however, occur in certain genera, where the 

 fertile females, or males, or both, are ergatoid, assuming the form 

 of thorax peculiar to the worker. 



The parts of the head, thorax and abdomen in an ant are 

 homologous with those in other hymenopterous insects, but are 

 generally modified. The subjoined figures give illustrations of some 



VOL. II. h 



