1906.] 



Wheeler, Relations of Ants to Plants. 



417 



bility because Vosseler ^ has recently seen some African ants which 

 actually accomplish a similar feat. These insects were very fond of 

 entering the immature flowers of Cohcea scandens and cutting away 

 the woolly accumulation of hairs at the base of the bell-shaped corolla 

 in order to reach the nectaries. When Vosseler plugged the opening 

 of the corolla with cotton, the ants gnawed holes in the base of the 

 flower and thus attained their end in the directest manner possible. 



3. MYRMICA AND THE SUN-FLOWER. 



Professor T. D. A. Cockerell has recently called my attention to a 

 third case of maladjustment in the relations of ants to plants. In the 

 neighborhood of Boulder, Colorado, he has repeatedly seen masses 

 of ants {Myrmica rubra hrevinodis var.) attracted 

 and killed by the sap that exudes from broken 

 stems and petioles of the sun-flower (Helianthus 

 annuus). This plant is very abundant in the 

 lower ground about Boulder, and its sap, as I 

 can testify from personal observation, becomes 

 excessively sticky on exposure to the air, so that 

 an ant that has once touched it with its legs or 

 antennge is held fast until it perishes. In this 

 case it is difficult to see how the plant can profit 

 by destroying the insects, for the catastrophe is 

 purely accidental, depending on an occasional 

 injury to the plant. A typical specimen showing 

 a number of dead ants partially embedded in 

 the inspissated sap, was kindly forwarded to 

 me by Professor Cockerell and is represented 

 in the accompanying figure. It is interesting 

 as showing on a small scale the way in which 

 ants and other insects became embedded in 

 such substances as amber and copal. 

 Professor Cockerell surmises that this fatal condition, in which, as 

 in the preceding instances, the ants succumb, may be due to the 

 meeting of two organisms originally belonging to widely separated 

 biogeographical environments; the Mynnica being essentially a 

 northern or subboreal species, while the sun-flower represents an 

 austral element which has, during comparatively recent times, in- 

 vaded the domain of the Myrmica. This view, which is certainly 



iVerhinderung des Fruchtansatzes bei Cobffia durch Ameisen. Zeitschr. f. wiss. Inseckt. Biol., 

 II, 1906, pp. 204-2CO. 



[Nov., 1906] 27 



Fig. I. — Broken twig of 

 Sunflower, showing ants 

 ( Myrmica brevinodis ) 

 caught and killed by 

 the exuding sap. 



