Page:Darwin - The various contrivances by which orchids are fertilized by insects (1877).djvu/36

16 hive-bees from ten to sixteen pollen-masses adhered; to the head of Eucera longicornis eleven, to the head of Osmia rufa several, and several to the bare surface close above the mandibles of Bombus muscorum. H. Müller has seen twelve different kinds of bees visiting the flowers of O. latifolia, which are also visited by Diptera. My son George observed for some time plants of O. maculata, and saw many specimens of a fly (Empis livida) inserting their proboscides into the nectary; and subsequently the same fact was observed by me. He brought home six specimens of this Empis, with pollinia attached to their spherical eyes, on a level with the bases of the antennæ. The pollinia had undergone the movement of depression, and stood a little above and parallel to the proboscis: hence they were in a position excellently adapted to strike the stigma. Six pollinia were thus attached to one specimen, and three to another. My son also saw another and smaller species (Empis pennipes) inserting its proboscis into the nectary; but this species did not act so well or so regularly as the other in fertilising the flowers. One specimen of this latter Empis had five pollinia, and a second had three pollinia, attached to the dorsal surface of its convex thorax. H. Müller has seen two other genera of Diptera at work on this orchis, with pollinia attached to the front part of their bodies; and on one occasion he saw a humble-bee visiting the flowers.

We now come to Orchis (sub-genus, Anacamptis) pyramidalis, one of the most highly organised species