PAM.MKL — POLLINATION OF PIILOMIS TUBEROSA. 259 



One Other case must be cited as showing how inteUigent the 

 actions of some insects seem to be. Bombus terrestris, which per- 

 forates the flowers of Galeobdolon hitetim in and about Lippstadt 

 (91 iii. c) sometimes flew to another flower without much hesita- 

 tion, and without making any attempts to perforate the flowers 

 or to get nectar in a normal way. On examination it was found 

 that some of the flowers had changed sh'ghtly in color, and that 

 these no longer contained nectar. The change in color was slight, 

 but to the acute color-sense of the insect it was sufficient to indi- 

 cate the absence of nectar. It is a well known fact that many 

 flowers change their color at'ter pollination when the secretion of 

 nectar has ceased, e.g. Eibes aiireum, Go&sypium herbaceuyn, JEs- 

 culus Hippo cast a num, many Boroginea', etc., for the apparent pur- 

 pose of indicating to insects that their services are no longer 

 needed, thereby saving them much waste of time in probing 

 such flowers. While this change of color in Galeobdolon was un- 

 doubtedly developed for a similar purpose, the insect in this case 

 utilize this physiological difference in color in obtaining nectar 

 in an abnormal way. 



Humble-bees show preferences in the flowers they perforate. 

 Dr. Wm. Ogle (25 b) states that in Switzerland he collected 100 

 flower-stems of a blue variety o( Ac on it urn I^'upellus without find- 

 ing a single flower perforated, while on 100 stems of the white 

 variety, growing near by, every one of the open flowers had been 

 perforated. This dift'erence, Darwin thinks, may be due to dif- 

 ferent amounts of acrid matter contained in the flowers, the blue 

 variety being distasteful to bees. 



In bringing the consideration of perforated flowers to a close, I 

 must cite a few cases showing that the perforations are made at 

 the proper point, so that they are of the greatest service. A inost re- 

 markable case has been alluded to in Lathyrus sylvestris. Darwin 

 (25 c) states that in Stachys coccinea one or two slits were made 

 on the upper side of the corolla near the base. In Salvia men- 

 thcefolia (*S'. Grahaini) the calyx is somewhat elongated, so that 

 both calyx and corolla were invariably perforated. In Antirrhi- 

 num majus one or two holes are made on the lower side close to 

 the nectary. In Aquilegia and Aconitum they are made in the 

 spurs, sometimes on one side or on both sides. In Phlotnis tube- 

 rosa slits were always made immediately above the enlargement 



