1924 ] 
Flower Visits of Insects II 
93 
FLOWER VISITS OF INSECTS Il4 
By Charles Robertson. 
Carlinville, Illinois. 
Hymenoptera (ex. bees). 
The lower Hymenoptera, 26 per cent of the visitors observed, 
make only 16.8 per cent of the visits. Of the 437 insect flowers 
observed, they occur on only 43 per cent, while the bees occur 
on 95.4 per cent. The only respect in which they resemble the 
bees and show more efficiency than the flies and Lepidoptera 
is in the thick proboscides composed of several appendages, so 
that on many flowers they are more apt to transfer pollen. The 
flowers showing the greatest numbers of these insects are Cicuta 
maculata 145, Sium cicutcefolium 95, and Pastinaca sativa 91, 
with exposed nectar, and Pycnanthemum flexuosum 89, and 
Solidago canadensis 81, with concealed nectar. 
Of the visits of the lower Hymenoptera, 95.5 per cent are to 
social flowers, usually with epigynous nectaries. It is held here 
that these insects have produced no special flowers. They 
resort to highly specialized social flowers which have been mod- 
ified by bees. They may have had some influence in further 
modifying these, especially in the case of fig flowers. 
The ecology of lower Hymenoptera is associated with 
insects on which they are parasitic or with which they provision 
their nests. They are therefore most abundant in summer when 
all except Tenthredinidse reach their maxima. They have no 
^The first number was published in Psyche 30; 158-69, 1923. In the 
table on page 158 the local flora should be 560, with percentages as follows: 
Ma 27.5, Mi 28.9, Mas 17.3, Mis 21.4, Pol 4.8, Red 29.4, White 39.8, Yellow 
30.7. Of the 493 indigenous flowers the percentages are: Ma 25.9, Mi 29.6, 
Mas 17.0, Mis 22.7, Pol 4.6, Red 29.0, White 40.3, Yellow 30.6. On page 
159, line 4, for “41.6” read “about 48”. In line 32 “ruby-throated” came from 
an abortive attempt to shorten “ruby-throated humming-bird” to “ruby- 
throat.” On page 167, line 24, for “seventy” read “seventy-three.” Besides 
the tables mentioned there, each one of the 1288 visitors has its visits dis- 
tributed under the classes and colors as shown in 3, 173. 
