1913] The Ottawa Naturalist. 151 



THE MILKWEED AND INSECTS. 



In connection with Mr. Sladen's note in the December 

 number of The Naturalist telling of the bee with the pollinia 

 of Asclepia attached to its feet, and describing the remarkable 

 method of cross fertilization adopted by this plant, it may be 

 of interest to remark that Asclepia's device to ensure the effective 

 dissemination of its pollen causes in the case of our native 

 A. syriaca at least the death of large numbers of insects. The 

 pollinia are so difficult, comparatively, to withdraw, that they 

 can be removed from their cells only by strong insects like the 

 larger species of bees. Less sturdy seekers after nectar which 

 get their feet caught in the clips, as recounted by Mr. Sladen, 

 are not able to pull out the pollen masses. Their struggles seem 

 onlv to wedge their legs more firmly in the narrow fissures of 

 the corolla, and unable to free themselves, these hapless guests 

 at the Caesar Borgia feast spread by the plant, die a lingering 

 death. 



Manv different kinds of insects, such as flies, beetles, gnats, 

 wasps, bees, and small butterflies and moths, come thus to an 

 untimely end, but in my experience, by far the most frequent 

 victims are ants. ' An examination of the blossoms of A. syriaca 

 growing in the vicinity of ant colonies never fails to discover 

 some of these exemplars of Solomon caught fast in the manner 

 described, some still vainly struggling for freedom, others, 

 hanging dead like gibbetted malefactors. 



This destruction of insect life is apparently merely accidental, 

 and seems to be of no particular use to the plant . For, of course, 

 Asclepia is entirely devoid of any such digestive apparatus as is 

 found in the sundews and pitcher plants, and cannot utilize the 

 dead insects in any way as food. Doubtless, cross fertilization is 

 much better accomplished by the stronger flying insects, which 

 are capable of carrying the pollinia farther and safer than the 

 weaker flyers or the crawlers, but death seems a rather severe 

 discipline of the latter for their undesired visit. 



Charles Macnamara, Arnprior, Ont. 



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