Insects Visiting Blossoms of Spirea 135 
others. Later when Solidago gramintfolia is in full bloom 
and is very abundant these blossoms are sought by the yellow 
jackets in great numbers. Even at this time, however, a 
proportional number apparently visit the few spirea blossoms 
remaining. Regarding the seasonal distribution of the yellow 
jacket and of other species of the same genus, as would be 
expected of a colonial form, there is a rather gradual numeri- 
cal increase during early and midsummer and a very rapid 
increase later in the season. This rapid increase in 1917 
commenced during the first week in August and by the 
middle of this month this species was so common that speci- 
mens were no longer retained. However, it was apparent 
that they were rapidly increasing in numbers up to the time 
observation ceased, September 2, at which time individuals 
of the various species of Vespula far outnumbered all other 
flower visitors combined. 
Bremus (Bombus) terricola Kirby. This bumble-bee, 
which apparently is the most common one frequenting spirea 
blossoms in the Elka Park region, may be used as an example 
of the genus. Its seasonal distribution as shown by ‘its rela- 
tive abundance upon spirea is similar to that of the yellow 
jacket although it is never quite so numerous. This is to be 
expected from the similarity in habit between these forms 
both of which are colonial forms and visit the blossoms in 
search of honey and pollen. 
The data regarding most of the remaining Hymenoptera 
is not complete enough to warrant important conclusions. In 
the case of such forms as the various species of Psammo- 
chares, Odynerus, Humenes, Solenius and Cerceris, the visits 
of which to spirea blossoms are probably as likely to be in 
search of prey as for obtaining honey or pollen, we would 
not expect much uniformity of occurrence. Therefore a 
curve showing the numbers occurring at stated periods on 
one particular species of flower would not be so lkely to 
represent the true seasonal distribution of the species because 
prey could likely be obtained from many other sources. 
The ants listed above, the species of which were kindly 
determined by Mr. M. R. Smith of the Bureau of Ento- 
