MONARDA FISTULOSA. 79 



MONARDA FISTULOSA. 



NORMAL POLLINATION. 



Habit and structure. — This species grows in fairly dense groups on 

 warm half-gravel slides, the numerous stems of each plant making a brilliant 

 mass of color. This attractiveness is due in large measure to the capitate 

 clusters of bright pink-purple flowers. The latter are erect or ascending, 

 and consist of a slender tube with two long lips. The upper lip is subulate 

 and protects the anthers and stigmas when young, while the lower is strap- 

 shaped and forms a landing-platform. The anthers are reduced to two, 

 and the nectar is abundant, so that the flowers are visited almost wholly 

 for nectar. Since the flowers bloom late in the summer, they constitute 

 the chief attraction to the butterflies and larger bees at this time (plates 

 13 and 16). 



Behavior. — Bombus juxtus lands on the lower lip of the corolla and 

 sucks nectar through the tube, pollinating the flower as its head rubs against 

 the anthers or stigma. One B. juxtus was observed stealing nectar from 

 the base of the corolla-tube, but this was not the normal procedure for the 

 species. B. bifarius, proxirnus, and pennsylvanicus robbed Monarda through 

 holes at the base of the tube during several seasons in succession, but in 

 1922 all the individuals observed secured nectar in the normal way. The 

 year previous Bombus proxirnus was observed puncturing the corollas in 

 one group without making a single normal visit, while in a second group a 

 few yards away it just as regularly obtained nectar in the proper manner. 

 Andrena crataegi is unable to make holes easily in the corolla-tube and con- 

 sequently takes advantage of those made by other species. Prosopis 

 elliptica stands on the lower lip of the corolla and eats the pollen fallen from 

 the stamens. Halictus pulzenus alights, walks around on the anthers, 

 and then goes down the filaments to the nectary. It gathers pollen from 

 the anthers, but it does not come in contact with the stigma, except by 

 accident. 



Erynnis leonardus snowi alights on the corolla lip, unrolls its ligule, and tries 

 to find the nectar. The ligule often slips along the outside of the tube, and 

 even when it starts down the tube it is withdrawn occasionally as if the 

 butterfly were uncertain. The latter does not have very good control of the 

 ligule and its eyes are apparently so placed that it can not see down the tube 

 to guide this by sight. The difficulty experienced by Erynnis is probably 

 due to its landing at the margin of the head. This is indicated by the fact 

 that Argynnis atlantis regularly alights in the center, the angle of the ligule 

 approaching that of the corolla-tube and thus rendering the insertion of 

 the ligule much easier. The control of the larger butterfly is perhaps 

 greater also, as it has little difficulty in inserting the tongue in shortened 

 corollas on the first trial. As a consequence, this species works on Monarda 

 with something of the rapidity of Bombus. Selasphorus platycercus is a 

 frequent visitor to these flowers, where it poises in the air in front of the 

 flower-head and works very rapidly. It pushes its bill into every flower 

 and is a very effective pollinator. The fluttering motion rubs the bill and 

 feathers on the front of the head against the stigma and also collects pollen 

 from the anthers. 



