2 HYMENOrTERA ACULEATA. 



■wings. In the social groups a second form of the ? exists, 

 in which the ovaries are not fully developed. Such females 

 are genei'ally called " workers," and in the Heterogyna or 

 ants are always wingless. By social species is understood 

 those of which many individuals combine in making a 

 common nest. Of these there are three groups, the 

 Heterogyna or ants, the Vespidee or true wasps, and the 

 higher Apidse, which include the humble bees and the 

 hive bee. All the rest are solitary, one ? making and 

 provisioning its own nest. Many of the solitary species 

 occur in colonies, and this habit of colonization is considered 

 by some to be a tendency towards socialism. In general 

 foi'm the Aculeata may be said to vary comparatively very 

 little, especially among the Anthophila. The specific 

 characters are often most obscure, and frequently the females 

 of two species are so alike that in the absence of the c? 

 their real names cannot be assigned to them with certainty. 

 The genera are more easily defined, but the difficulty 

 of discovering characters by which to sort the genera 

 into families or groups is very great. The males and 

 females are often very dissimilar, and in some groups 

 rarely occur together. The inquiline (or cuckoo) genera, 

 of which there are many among the Anthophila, call for 

 special notice. Their species inhabit the ?ame nest or lay 

 their eggs in the same burrows as the bees to whom the 

 nests belong. They apparently do nothing towards the 

 economy of the family into which they intrude, but lay their 

 eggs so that their offspring shall have a better chance of 

 nourishment when hatched than that of their hosts. Yet, 

 notwithstanding this, they appear to live on friendly terms 

 with the owners of the nests, and generally closely resemble 

 them in appearance, although in a few cases the dis- 

 similarity between them is very strongly marked. The 

 inquilines, however, are always destitute of the specialized 

 organs fur pollen collecting which characterize their 

 hosts. 



