270 NATURAL SCIENCE. Oct., 



aphids and coccids — the "domestic animals" of the ants. If, 

 through any cause, the aphids left the place, the ants went away too. 



To modern naturalists the stages by which the more perfectly 

 social insect communities have arisen furnish a question of great 

 interest. Some facts and suggestions towards the solution of this 

 problem have recently been furnished by Herr Verhoeff (8). He 

 points out that the economy of each social group must be compared 

 with that of the " solitary" genera most nearly akin to its presumed 

 ancestral stock. The affinities of the ants are considered by Verhoeff 

 too doubtful for profitable consideration : he therefore confines his 

 attention to the wasps and bees. The social wasps (Vespidae) are 

 believed to have arisen from the Eumenidae, and these from a group 

 of fossorial hymenoptera nearly allied to the Trypoxilidae. The bees 

 are supposed to have originated from some other fossorial family. 

 Hence the study of the fossorial genera may be expected to throw 

 much light upon the economy of the higher groups. From simply 

 laying the egg in the body of some other insect — after the manner of 

 modern ichneumon flies— was developed the present habit of the 

 fossorial wasps of digging a hole, in which are placed both the egg, 

 and the insect which serves as a prey for the grub when 

 hatched. The habit of catching the prey, and then digging a hole 

 to bury it in, must clearly have preceded that of first preparing the 

 hole and then catching the prey to put in it. As in primitive man, 

 the hunting habit was at first stronger than the home-making. But 

 the simple digging of a hole, once adopted, led on by degrees to the 

 construction of nests of a more and more complicated design. The 

 simple unicellular nest was improved into the linear arrangement of 

 cells, with a common opening, constructed either in the earth or in 

 twigs which may now be observed in species of Crabro, Hoplopus, 

 Tropoxylon, Colletes, Osmia, Anthopkora, etc. From this latter, or from 

 the simple cell, is derived the branched style of nest in which the 

 cells open off from the entrance or from a passage leading thereto ; 

 such nests are made by many of the solitary wasps and bees, species 

 of Hoplopus, Halictus, etc. In Rhopalum clavipes, which, making its 

 nest in twigs, constructs some of the cells at a very slight angle with 

 the main series, we see how the branched system could arise from the 

 linear. A further advance is seen in the nests not placed in cavities 

 but built of lime or sand upon rocks or walls. The highest forms of 

 nests are the paper structures of the social wasps, and the waxen 

 cells of the bees. 



Herr Verhoeff does not believe that the social communities of 

 the wasps and bees have arisen from casual colonies, such as aie 

 occasionally observed among solitary species ; the bond of the com- 

 munity is to be found in the members being all the offspring of one 

 mother. As in human society, the family has given rise to the state. 

 For the development of a social community three conditions are 

 necessary : — A nest large enough for a number of insects, a close 



