_Sphecoidea._--In this division are included the rest of the "digging-wasps," distinguished from the _Vespoidea_ by the short pronotum not reaching backward to the tegulae. They have usually been reckoned as forming a single, very large family--the _Sphegidae_--but ten or twelve subdivisions of the group are regarded as distinct families by Ashmead and others. Great diversity is shown in the details of structure, habits and nature of the prey. Species of _Sphex_, studied by Fabre, provisioned their brood-chambers with crickets. _Pelopoeus_ hunts spiders, while _Ammophila_ catches caterpillars for the benefit of her young. Fabre states that the last-named insect uses a stone for the temporary closing of her burrow, and the Peckhams have seen a female _Ammophila_ take a stone between her mandibles and use it as a hammer for pounding down the earth over her finished nest. The habits of _Bembex_ are of especial interest. The female, instead of provisioning her burrow with a supply of food that will suffice the larva for its whole life, brings fresh flies with which she regularly feeds her young. In this instinct we have a correspondence with the habits of social wasps and bees. Yet it may be thought that the usual instinct of the "digging-wasps" to capture and store up food in an underground burrow for the benefit of offspring which they will never see is even more surprising. The habit of some genera is to catch the prey before making their tunnel, but more frequently the insect digs her nest, and then hunts for prey to put into it. _Apoidea._--The bees which make up this group agree with the Sphecoidea in the short pronotum, but may be distinguished from all other Hymenoptera by the widened first tarsal segment and the plumose hairs on head and body. They are usually regarded as forming a single family--the _Apidae_--but there is very great diversity in structural details, and Ashmead divides them into fourteen families. The "tongue," for example, is short and obtuse or emarginate in _Colletes_ and _Prosopis_, while in all other bees it is pointed at the tip. But in _Andrena_ and its allies it is comparatively short, while in the higher genera, such as _Apis_ and _Bombus_, it is elongate and flexible, forming a most elaborate and perfect organ for taking liquid food. Bees feed on honey and pollen. Most of the genera are "solitary" in habit, the female sex being undifferentiated; but among the humble-bees and hive-bees we find, as in social wasps and ants, the occurrence of workers, and the consequent elaboration of a wonderful insect-society. (See BEE.)