CHAMAENERIUM ANGUSTIFOLIUM. 

 Table 35. — Visitors to flowers with floral envelopes removed. 



49 



Bombus juxtus readily distinguished between buds and these mutilated 

 flowers, for it never stopped at the former. 



Upper petals and the included sepal removed. — This sepal is just 

 behind the opening to the nectary and looks as if it might be a guide to 

 it. Bombus juxtus went to flowers with these parts removed and to normal 

 flowers indiscriminately, just as they happened to be in its path. 



Stamens and style removed. — Bombus juxtus visited flowers with 

 these parts removed and found the nectar at once. It went to three 

 flowers in succession, but had some difficulty hanging on. 



The following notes made during 5 minutes of observation indicate that 

 Bombus juxtus took little notice of all the above changes. An equal number 

 of normal and mutilated flowers were under observation. 



10 h 20 m Bombus juxtus flew over flowers with 

 the corolla removed, but stopped 

 at 2 with the stamens alone gone. 

 A second one stopped at 2 

 flowers with the petals gone and 

 at 3 normal ones. 



10 21 B. juxtus, 2 flowers with stamens gone. 



10 h 22 m B. bifarius, 3 flowers with the upper 

 3 petals gone and 3 normal. 



10 23 B. juxtus, 4 normal and then 2 flowers 

 with the upper petals gone. 



10 24 B. juxtus, 3 flowers with the upper 

 petals gone and 2 normal. 



10 25 B. juxtus, 5 normal. 



The relative numbers of visits made by the various species of bees to the 

 different kinds of mutilated flowers, as well as to the normal ones, are shown 

 in table 36. On July 17 and 18, 10 normal flowers and 5 mutilated ones of 

 each type were used, one or more of each being placed in each raceme; the 

 time of observation was 1 hour. For the next two periods of an hour and 

 a half each, 4 flowers of one kind were arranged on each stalk. 



The results obtained in this experiment relate chiefly to the behavior 

 of Bombus, as the other 4 genera made but 17 of the 210 visits recorded. 

 Of the 193 visits by bumble- bees, B. juxtus made 173 and B. bifarius but 

 20. The actual number of visits to normal and mutilated flowers is nearly 

 equal, but the normal flowers were a third as numerous and hence about 

 twice as attractive. However, the contrast between the different types of 

 mutilated flowers is so sharp as to indicate an intentional selection. Thus, 

 flowers with the perianth, stamens, and styles removed received but 6 

 visits out of a total of 114 for mutilated flowers, while those with either 

 stamens or styles excised obtained less than half as many as those with 

 petals or both sepals and petals removed. On the other hand, the visits 

 to both the latter were a third less tnan to the flowers with the stamens and 

 styles excised but the perianth intact. While the results are not entirely 



