178 
within its walls. Three species of mud-daubers (Sceliphonin1) 
were the most conspicuous builders, and two species of these 
wasps, and the two, inch-long Eumenes dwelt in the forest as 
well. 
The various wasp enemies, Ichneumonidae, Bombyliidae and 
Chrysididae, were also present indoors. 
While there appears to be a tendency towards social life in 
several widely-separated groups of wasps, the vespoid forms are 
the only ones through which it has been brought to a conclusion 
and become an accomplished fact—in the Vespinae. 
We find true social life in the Hymenoptera characterized by 
several elements, chief of which are: the division of labor, 
marked in the higher forms by three phases, viz: egg-laying fe- 
males or queens, sterile females or workers, and males—then we 
have the more or less elaborate communal nest, which may afford 
shelter for both adult and young wasps—and finally, the habit of 
feeding the wasp-grub from time to time until it is full grown. 
A strongly-developed instinct to defend the nest is also present 
in the majority of social wasps. 
Now, there are a number of solitary wasps which possess one 
or more of these traits. Many of the Bembecidae, sand wasps 
which often live in colonies, feed their young from day to day; 
others of this family lay the egg before storing any food, and 
some Microbembex provide their young with food in several in- 
stalments and close up the cell before the grub is full-fed. The 
Peckhams (1898) have noted that the American larrid, Lyroda 
subita, feeds her young from day to day, while Ammobia mutica 
of the Philippines may continue to store a cell with grasshoppers 
‘until her larva has reached a considerable size. 
It does not appear to the writer, however, that the cases just 
mentioned indicate progress towards social life. With some of 
these wasps, as Ammobia mutica, and possibly Microbembe.x, it 
suggests a prey or food difficult to secure at all times—hence 
the more or less protracted period required to fully store the cell. 
The erratic Bembex do not show an industry commensurate with 
their activity, and they probably feed their young with as many 
flies as they are able or feel inclined to catch in a day. 
Some Psammocharidae, as Macromeris, Paragenia, and prob- 
ably a few Pseudagenia, of the eastern tropics, manifest habits 
which more nearly approach those of the Vespinae. The Psam- 
mocharidae are lower down in the scale of development than the 
Vespinae, and have arrived at this relative specialization as an 
independent branch, which, if further developed, would termi- 
nate perhaps in a group of social wasps parallel, but not closely 
related to our present communal forms. While these interesting 
