APRIL 15, 1913 



267 



IS ALFALFA POLLINATED BY BEES? 



Some Interesting Points in the Discussion 



The following article appeared originally in the 

 Dakota Farmer, on page 61, by A. O. Stevens, of 

 the North Dakota Agricultural College. One of our 

 subscribers, Mr. Jess Dalton, questions the correct- 

 ness of Mr. Stevens' statements, and desires to make 

 a reply. In order that the reader may better under- 

 stand it, we are publishing this article entire. — Ed. 



BEES AND THE ALFALFA SEED CROP. 



In the December 15th issue of The Dakota Farm- 

 er appeared an article referring to the value of the 

 honeybee as a pollinator of the alfalfa flowers. The 

 article in question is quoted for the most part from 

 The Country Gentleman, and begins thus: 



" Very few data are at haud relative to the value 

 of insects in the production of a seed crop." This 

 is quite true ; but it is also true that most of the dis- 

 cussions on the subject appear to have been written 

 without a knowledge of the data which are available. 

 Nearly half a century ago it was made known by 

 men of no less authority than Mueller and Henslow 

 that the bee visits the alfalfa flowers without effect- 

 ing pollination. 



Far be it from the wr-iter to discourage the bee 

 industry, especially in connection with such a valu- 

 able honey-plant ; but the subject has been treated 

 so frequently without due regard to the facts that it 

 seems desirable to present a brief survey of the sit- 

 uation. 



In order to understand the conditions it will be 

 necessary to call attention to the flower structure. 

 The stamens and pistil of each flower are enclosed 

 by the two inner petals (which are united along the 

 lower edge, and are known as the "keel"). The 

 pollen-bearing portions are thus entirely concealed, 

 and are not e.xposed to visiting insects. When, how- 

 ever, a pressure is applied inward and downward 

 upon the keel petals, a certain tension is released, 

 which causes the stamens to snap upward with con- 

 siderable force. This may be readily observed by 

 using a toothpick or other pointed object. If this 

 pressure is applied by a bee, the pistil (which is 

 enclosed by the united filaments of the stamens) is 

 thrust against the insect's body, and pollen is rub- 

 bed upon the insect by the stamens. As the pistil 

 projects slightly beyond the stamens, it is likely to 

 receive first the pollen left by a flower previously 

 visited. 



The bee, however, rarely inserts its tongue at this 

 vPart of the flower, but thrusts it between the two 

 outer petals, leaving the stamens undisturbed. The 

 bees are easily observed, and any one may satisfy 

 himself on this point. In one trial by the writer at 

 Manhattan, Kansas, in 1909, the visits made to 584 

 flowers were observed in about an hour. Of these, 

 only nine were tripped by the bees. 



Concerning the effectiveness of other insects, prac- 

 tically no data of value are available so far as is 

 known to the writer. The insects usually mentioned 

 are butterflies, bumblebees, and " wild bees." The 

 butterflies are common visitors, but seem to be of very 

 little if any value. Bumblebees, according to a few 

 observations made the past summer, often reach the 

 nectar in the same way as the honeybees, although 

 they seem to trip the flower more frequently. 



The wild bees are practically unknown except to 

 those who have given them special study. Every 

 locality with an average number of native plants 

 has one or two hundred different species of these 

 bees, so that the expression, " where insect life is 

 scarce," is hardly applicable to many cases. By no 

 means all of these are adapted to such a flower as 

 that of alfalfa. In the limited observations which 

 the writer has been able to make, the only bees 

 which tripped the flowers regularly were the leaf- 

 cutters (Megachile) . These and their near relatives 



may be distinguished by the fact that the females 

 collect pollen on the under side of the abdomen. The 

 species chiefly' observed is nearly as large as the 

 honeybee, and with a tongue of nearly equal length. 

 Another common one is about one-half larger than 

 the honeybee, and with a longer tongue. On the 

 whole these bees seem better adapted than nearly all 

 ftie others to this plant. The species are very nu- 

 merous, and are found over nearly all the world. 



Now that the probability of insect pollination has 

 been reviewed, the necessity of it needs a little at- 

 tention. To quote again the previous article: "At 

 the Kansas Experiment Station, alfalfa plants cover- 

 ed with a w^ire netting * * made no seed, whereas 

 those plants that were adjacent but uncovered were 

 filled with seed-pods." This reference seems to be to 

 bulletin No. 155 where some such statement is made, , 

 but without details or data. Another bulletin of the 

 same station (No. 151) presents unmistakable evi- 

 dence to the contrary. A careful study of the data 

 presented seems to indicate that, while insects may 

 be important, there are some unknown factors, phys- 

 iological or otherwise, of greater consequence. All 

 of the plants covered with wire cages, and left un- 

 disturbed, produced seed, but at greatly varying 

 rates ; those having but little, also being light pro- 

 ducers in the open field. If a calculation be made 

 from the plant producing the most, a ton of green 

 plants would yield 8 Vs pounds of seed. On the same 

 basis for five plants which were divided, half of 

 each plant being covered and hand-pollinated, the 

 other half permitted to be insect-pollinated, the 

 average would be 10.4 pounds for the hand-pollin- 

 ated, and 11.8 pounds for the insect-pollinated. 

 Again, from twenty-six plants, hand-pollinated, the 

 average would be 5.8 pounds, and the highest 68 

 pounds, per ton of fresh plants. There was also a 

 great variation in the per cent of flowers producing 

 seed, and this did not correspond to the amount of 

 seed per weight of plant. 



Burkill, who investigated the subject quite care- 

 fully in England, did not secure seed from untrip- 

 ped flowers unless he pinched or rubbed the tip of 

 the pistil. He seems to have inferred that the strik- 

 ing of the pistil aginst the insect's body was an es- 

 sential point. It is well known that injuries to 

 plants often induce fruitfulness, and perhaps the 

 dragging of an alfalfa-field may act in this way in 

 addition to tripping the flowers. 



This was submitted to Mr. J. H. Loveil, 

 of Waldoboro, Maine, whom we regard as 

 the best authority ou the pollination of 

 plants by insects, perhaps, in the United 

 States. He has done a vast amount of 

 field work in investigating the subject of 

 pollination. He is an entomologist, a bot- 

 anist, and at the same time a beekeeper. 

 We have submitted this to him for his ex- 

 amination, asking that he give us his views 

 for publication. At the same time, we sug- 

 gested that, when a plant has nectar, color, 

 and odor, it has these properties for a pur- 

 pose — to invite the visitation of insects — 

 bees in particular. ]\Lr. Lovell's reply is 

 interesting and valuable, and we think it 

 shows conclusively that bees, so far from 

 being of little or no value in pollinating 

 the blossoms of alfalfa, are a vei-y impor- 

 tant factor in increasing the seed crop. We 

 will now let Mr. Lovell speak for himself: 



Dear Mr. Boot : — Your favor of the 13th 

 instant is at hand, with enclosures as stated. 



