150 
Psyche 
[September 
comb. One nest of P. rubiginosis was built a second year in the 
same site as the first, in the narrow space between two boards in 
an old refrigerator car. The result was that the second comb was 
attached to and below the first, giving the nest the appearance 
of the combs of Vespa. This was merely an accident due to the 
narrowness of the space, combined with the persistence of the 
rubiginosus queens in returning to their old home in the spring. 
But it is just by such accidents that new habits get a foot-hold. 
In another place, I found a nest in the narrow space between the 
inner and outer walls of a barn. Here one tier of cells was built 
below the other, much after the manner of comb-building in 
tiers by the Vespine wasps. This may point to the rise and 
evolution of the habit of arranging combs in tiers. Who knows 
but that Vespa at one time may have built single combs as do 
Polistes to-day, and who knows further but that a similar acci- 
dent of crowding may have caused her to build tier below tier 
until to-day we have this practice fixed in the habits of the 
Vespa? 
Explanation of plate IV. 
Fig. 1 . Polistes annularis seeking shelter from the cold in an old nest of 
Polistes pallipes 
Fig. 2. Nest of Polistes pallipes built in a tight corner. 
Fig. 3. A sky-scraper nest of Pollistes pallipes. 
Fig. 4. Nest of Polistes rubiginosus. 
