BEES, WASPS, ANTS, ETC. 525 



which is applied by certain authors who consider the group thus formed as of equal 

 value with Fossores, as applied to tlie remaining three families. 



The fossorial Hymenoptera are, as the name implies, diggers. This habit is char- 

 acteristic of the group, but is not distinctive, as certain of the true wasf)s dig similar 

 nests. The members of this group are solitary iu their habits. Their legs are fitted 

 for walking and burrowing only, and arc not adapted to the collection of pollen, nor 

 is the body ever clothed with hair fitted for the transportation of pollen, although cer- 

 tain species are hairy. The wings lie flat when- at rest. This character!, as contradis- 

 tinguished from the fold in the wings of the true wasps when at rest, furnishes a ready 

 method of distinguishing a digger from a true wasp, while the absence of polleuiferous 

 organs offers an equally available distinction from the bees. 



In the fossorial Hymenoptera, a single female, working alone, prepares a nest for 

 her offspring. This is usually done by excavating a hole in the ground or in wood, 

 and placing therein a store of food consisting of spiders or of other insects, most often 

 larv£e. An egg is then laid with the store, and the hole is closed. When tlie larva 

 leaves the egg it finds itself upon a supply of food sufficient to last it until it is fully 

 grown. The transformations are all undergone within the burrow, and the adult 

 insect emerges soon after reaching the perfect state. 



As a rule, each species exhibits a preference for a particular kind of food. Thus, 

 the nests of one species will be found filled almost exclusively with spiders, of another 

 with saw-fly larvae, of another with beetles, of still another with caterpillars, and so 

 on. Sometimes these stored-up insects are killed outright, but more often they are 

 stung in such a way as to paralyze all motion, thus preventing them from injuring 

 the eggs and young larvae, and at the same time keeping them fresh for an indefinite 

 period. 



In many cases the hole excavated for this nest reaches a considerable depth, and is 

 divided into a series of compartments, in each of which is placed a store of food and 

 an egg. Some species, instead of digging burrows, make cells of mud, carefully select- 

 ing the material from which the cells are composed. Each cell is provisioned and 

 supplied with an egg, as just described. 



Certain species, instead of constructing nests for themselves, search for burrows 

 made by other species, or for natural tubes, such as the interior of straws, in which to 

 store their supplies ; while others, again, lay their eggs in the already provisioned nests 

 of other species, thus becoming inquilinous in their habits. A very few members of 

 this group may be said to be truly parasitic. The adult insects are active, fly in the 

 hottest sunshine, and arc often found frequenting flowers. The females are some- 

 times wingless, and all of this sex are armed with powerful stings. 



The following artificial arrangement will be found useful in separating the families 

 of this group. In the first four families the pronotum extends on the sides to the base 

 of the wings. In the Sphegidse it does not. In the Mutillidaj and Scoliidfe there is a 

 contraction on the ventral surface of the abdomen at the union of the first and second 

 abdominal segments. In the Lapygidae and Pompihdse the ventral aspect of the abdo- 

 men is uniformly convex. In the Mutillidae the intermediate coxae are approximate 

 and the females are uniformly wingless, while in the Scoliidae the middle coxae are 

 widely separated and the females are nearly always winged. The Lapygidae and 

 PompilidiE are readily distinguished by their relative length of leg. In the former 

 the posterior tibiiu do not reach the caudal end of the abdomen, and in the latter they 

 extend beyond this point. 



