HYMENOPTERA. 113 



the Bees ; in the Wasps they are more globular, and affixed by 

 their smaller somewhat pedicelled end to the side, near the bot- 

 tom of the cell in which they are laid. The eggs of the lower 

 families tend to assume a spherical form. The eggs of dif- 

 erent species of Bombus present no appreciable differences. 



The larvae of the Bees and Wasps, especially the social 

 species, which live surrounded by their food, are of a very 

 persistent form, the various genera differing but slightly, while 

 the species can scarcely be separated. Such we have found to 

 be the case in the Bees and Wasps ( Vespidce) and Fossorial 

 Wasps. The sexes of the species with a very thin tegument, 

 such as Apis, Bombus, and Vespa, can be quite easily distin- 

 guished, as the rudiments of the genital armor can be seen 

 through. 



The Hymenoptera are mostly confined to the warmer and 

 temperate regions of the earth ; as we approach the poles, the 

 Bees disappear, with the exception of Bombus, and perhaps 

 its parasite Apathus ; a species of Vespa is found on the Lab- 

 rador coast, which has a climate like that of Greenland. No 

 fossorial species of Wasps are known to us to occur in the arc- 

 tic regions, while a few species of Ants, and several Chalcidi- 

 dce and Ichneumonidce are not uncommon in Northern 

 Labrador and Greenland. Our alpine summits, particularly 

 that of Mt. Washington, reproduces the features of Northern 

 Labrador and Greenland as regards its HymenopterouB fauna. 

 The tropics are, however, the home of the Hymenoptera, and 

 especially of the Bees. 



There are estimated to be about twenty-five thousand living 

 species of this suborder, and this is probably a much smaller 

 number than are yet to be discovered. 



In geological history, the Hymenoptera do not date far back 

 compared with the Neuroptera and Orthoptera, and even the 

 Coleoptera. Indeed they were among the last to appear upon 

 the earth's surface. The lower forms, so far as the scanty 

 records show, appeared first in the Jura formation ; the Ants 

 appear in the Tertiary period, especially in amber. 



As we have noticed before, the Hymenoptera are more purely 

 terrestrial than any other insects. None are known to be 

 aquatic in the early stages, and only two genera have been found 

 8 



