74 



NORMAL AND EXPERIMENTAL POLLINATION. 



lecting pollen at the time. As B. bifarius leaves the flower, it scrapes 

 pollen from the dorsal surface of its thorax with its front legs and places it 

 on the hind ones. One individual started to suck nectar in the normal 

 position, and then turned upside down and scraped pollen. Another 

 individual behaved in the same manner on one flower and then visited the 

 next flower in the normal way. The third landed, at once turned upside 

 down, and commenced scraping pollen, working in the same fashion 

 on three flowers in succession. The assumption of the normal or inverted 

 position by B. bifarius apparently depended on whether it came for nectar 

 or pollen. 



Apis mellifica is so large that only its head and half of its thorax can 

 enter the corolla-tube. These parts are hairy, and after sucking nectar 

 the bee comes out dusted with pollen. Titusella pronitens stands with its 

 hind legs on the lower recurved petals and the front ones on the corolla- 

 tube, while it pushes out its ligule and takes nectar. Anthophora simillima 

 inspects these flowers, but none land. Systoechus vulgaris has a tongue as 

 long as the corolla-tube, so long indeed that the head usually does not touch 

 the anthers or stigma in sucking nectar. If pollination is accomplished 

 by this fly, it is done by the ligule as it enters and leaves the corolla. Selas- 

 phorus platycercus is a very persistent visitor. In the course of a morning's 

 observation the same bird sucked nectar once or twice from every open 

 flower on the whole slope. This species worked so rapidly from flower to 

 flower that even when there were only one or two visitors every flower 

 in the locality was reached. 



Calendars. — The normal visitors to this species as observed during an 

 hour period on six different days are grouped in table 52. The first list 

 was made at the entrance to Englemann Canyon on June 13, when the 

 plants were past their prime and 212 open flowers on 30 spikes were in the 

 group. The second list was made on 82 spikes, bearing 526 open flowers, 



