Most species of hum'ble'bees have a longer proboscis than 

 either of the two kinds of honeyhees which have fceen 

 descrihed. They approach the flower in such a way, how- 

 ever, that a large proportion of the flowers are tripped. 

 The comparatively heavy weight of these insects,- part- 

 icularly of some of the larger species, appears to have 

 some influence in forcing the petals of the flowers apart . 



A count was made in 1907 of the numlser of flowers 

 which several different hees of the species of Megach ile 

 common at Pullma.n, Wash., tripped within a definite 

 period of time. One of these hees tripped 4 flowers 

 within 30 seconds; another tripped 12 flowers in one 

 minute and 10 seconds; while a third tripped 20 flowers 

 in 2 minutes and 15 seconds. These three "bees tripped the 

 flowers at the rate of an average number of 9.2 flowers 

 per minute or 552 flowers per hour. A single one of these 

 wild bees is capable of fertilizing a very large number of 

 flowers in one season, and if present in sufficient num- 

 bers would be an im_portant factor in fluencing the develop- 

 ment of the seed crop. At Pullman, ¥ash. , a large propor- 

 tion of the alfalfa flowers which produced seed in the 

 experimental plots, during the four seasons in which this 

 study was carried on there, were fertilized by these 

 insects. In the vicinity of Chinook, Montana, the numbers 

 of these bees or of any other honey-gathering insects 

 which are found there , and which trip the flowers that 



(47) 



