Wasps, Bees, and Ants 515 
shingles on a roof, beneath stones lying on the ground, and in Florida in the 
tubular leaves of a pitcher-plant.” 
Other common genera of solitary long-tongued bees are Anthophora 
{PL XII, Fig. 11), the species of which are hairy and robust-bodied, looking 
indeed much like small bumblebees, Melissodes and Synhalonia with very 
long antennas, rather like honey-bees in general appearance, and others 
of the great family Anthophoridas. All these bees agree in general habits 
with those already described, but every species presents an opportunity for 
interesting and valuable work by amateurs and nature-lovers in observing 
precisely its nest-building habits and life-history. No more attractive 
opportunity for outdoor observers offers than that of the field study of the 
solitary bees. 
As mentioned at the beginning of the discussion of the solitary bees, some 
species are parasitic or, more properly named, guest or inquiline in habit. 
That is, the females of these species, instead of building a nest-burrow of 
their own and storing it with food, lay their eggs in the nest-burrows of other 
bees, so that the larvae on hatching will be able to feed on the supplies stored 
up by the host-bee. This habit is not confined to a few species, but is com¬ 
mon to a surprisingly large number of solitary bees. Two entire families, 
including a hundred species of North American bees, are exclusively composed 
of parasitic bees (in addition a third parasitic family, an offshoot of the 
bumblebees, is mentioned in connection with the account, later, of the social 
bees). These two families are the cuckoo-bees, Nomadidae, mostly bright- 
colored species, metallic blue or green with the abdomen spotted or banded 
with yellow or white, and the Stelidae, differing structurally from the cuckoo- 
bees by having only two, instead of three, submarginal cells in the wings. 
Ashmead believes that the Nomadidae are descended from the Anthophoridae, 
and the Stelidae from the Megachilidae, the parasitic habit having arisen 
independently in the two groups. Howard mentions the interesting fact 
that the cuckoo-bees seem not only to be tolerated by their hosts, but that 
in some cases it has been observed that enough food is stored by the host- 
bee to enable the larvae of both host and guest to complete their development 
side by side and to issue simultaneously as adult bees. It may indeed be 
found, as has been discovered in numerous other cases of commensal life, 
that the cuckoo-bee gives, in some way, aid to the host, so that the living 
together is mutually advantageous. 
With the wasps there are no transition stages, among living forms, between 
a strictly solitary life, where each female makes her own independent nest- 
burrow, lays an egg in it and stores it with food, or brings food to the larva 
through its life, and the social or communal life exhibited by the yellow- 
jackets and hornets, where many females (of arrested sexual development, 
although not always to such a degree as to be actually incapable of producing 
