3 8 ° 
The Ohio Naturalist. 
[Vol. XI, No. 8, 
and to one side of the anthers. The stigmatic surface furnishes a 
convenient lighting place for insect visitors when they first 
arrive, thus affecting cross-pollination. 
Visitors: Diptera; Phthiria sulphurea, Lucilia caesar; Cole- 
optera; Disonycha pennsylvanica; Hymenoptera; 
Agapostemon splendens, Monarda maculata. A 
Bombus, probably B. americana, was observed 
but not taken. 
Rosaceae (Rose Family). 
Rosa Carolina. A not uncommon plant around the edge of the 
marsh or around ponds and swampy places. 
Visitors: Diptera; Eristalis americana , Eristalis tenax, Allo- 
grapta obliqua; Hymenoptera; Agapostemon radi- 
atus. 
Cactaceae (Cactus Family). 
Opuntia rafinesquii. This cactus, a true Xerophyte, has a yel- 
low flower that attracts many insects which may effect either self- 
or cross-pollination. The filaments are sensitive to mechanical 
stimulation. They incline inwards on being touched by insects, 
or even spontaneously, and thickly cover the stigmas with pollen. 
Autogamy thus regularly takes place and is always effective . 4 
In observing the opening of a bud it was noted that within ten 
minutes after the petals began to separate a visitor (Ceratina 
dupla) appeared and began delving into the base of the stamens. 
Here, as well as among some of the other flowers observed, it was 
noted that while a given insect is visiting certain flowers they 
usually confine themselves to that species alone, this of course 
being advantageous in effecting cross-pollination. 
Visitors: Coleoptcra, Trichius piger, Strigodcrma arboricola, 
Centrinus scutellum-album; Hymenoptera; Micro- 
bembex monodonta, Agapostemon radiatus, Bom- 
bus americana, Vespa borealis, Ceratina dupla. 
Cornaceae (Dogwood Family). 
Cornus amomum. “ Here the flowers are homogamous with 
exposed nectar, secreted by a ring surrounding the style. The 
stamens and stigmas develop simultaneously. The anthers are 
introrse and at the same level as the stigma, though some distance 
from it. Larger insects will effect cross-pollination while small 
flies and beetles, owing to their erratic movements, will sometimes 
effect cross-, sometimes self-pollination .” 5 
Visitors: Diptera; Lucilia caesar, Polenia rudis; Coleoptera; 
Cyrtophorus verrucosus, Cryptorhopalum triste; 
Hymenoptera; Elis plum pies, Polistes pallipes, 
Xylocopa virginica, Microbembex monodonta. 
4 See Op. cit., II. 45S-459. 
s Op. cit., II. 518-519. 
