142 Mr. C. Darwin on the Fertilization of Orchids. 



that it may be safely predicated that orchids with very long 

 nectaries, such as the Anacamptisy Gymnadenia^ and Platan- 

 thera, are habitually fertilized by Lepidoptera, whilst those 

 with only moderately long nectaries are fertilized by bees and 

 Diptera — in short, that the length of the nectary is correlated 

 with that of the proboscis of the insect which visits the plant. 

 I have now seen Orchis morio fertilized by various kinds of 

 bees, namely : — by the hive-bee {Apis mellificd) , to some of 

 which from ten to sixteen pollen-masses were attached ; by 

 Bombus muscorum, with several pollen-masses attached to the 

 bare surface close above the mandibles ; by Eucera longi- 

 cornis, with eleven pollen-masses attached to its head ; and 

 by Osmia rufa. These bees, and the other Hymenoptera 

 mentioned throughout these notes, have been named for me by 

 our highest authority, Mr. Frederick Smith, of the British 

 Museum. The Diptera have been named by Mr. F. Walker, 

 of the same establishment. In Northern Germany, Dr. H. 

 Miiller of Lippstadt found pollen-masses of OrcJiis morio at- 

 tached to Bombus silvarunij laindarius^ confusus, and pra- 

 torum. The same excellent observer found the pollen-masses 

 of Orchis latifolia attached to Si Bombus ] but this orchis is 

 also frequented by Diptera. A friend watched for me Orchis 

 mascula, and saw several flowers visited by a Bombus^ 

 apparently B. muscorum ; but it is surprising how seldom 

 any insect can be seen visiting this common species. With 

 respect to OrcMs maculata^ my son, Mr. George Darwin, has 

 clearly made out the manner of its fertilization. He saw many 

 specimens of a fly [Empis livida) inserting their proboscides into 

 the nectary ; and subsequently I saw the same occurrence. 

 He brought home six specimens of this Em-pis^ with pollinia 

 attached to their spherical eyes, on a level with the bases of 

 the antennae. The pollinia had undergone the movement of 

 depression, and stood a little above and parallel to the pro- 

 boscis : hence they were in a position excellently adapted to 

 strike the stigma. Six pollinia were thus attached to one spe- 

 cimen, 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 regu- 

 larly as the other in fertilizing the flowers. One specimen of 

 this latter Empis had five pollinia, and a second had three 

 pollinia, attached to the dorsal surface of the convex thorax. 



On nectar being secreted and contained betiveen the obiter 

 and inner membranes of the nectary in several species o/" Orchis 

 (p. 51). — I have repeated my observations on the nectaries of 

 some of our common species, and especially on those of Orchis 

 moriOj at the time lohen various bees were contimcally visiting 



