Mag^enta to Pink 



wings in motion, are the most useful, because in using tiieir legs 

 to offset tlie motion of their wings they rapidly repeat those 

 movements which are necessary to draw the pollinia from the 

 anther cells and insert them in the stigmatic chambers of other 

 flowers. "Large butterflies like Daiia/s, " si\ys Professor Rob- 

 ertson, " hold their wings still in sucking, spending more time 

 on an umbel, but generally carrying pollinia. Small butterflies 

 are worse than useless. They remain long on the umbels suck- 

 ing, but resting their feet superficially on the flowers. . . 

 Since several moths were found entrapped, pollination must often 

 be brought about by night-flying Lepidoptera. As a rule, Diptera 

 (flies) either do not transfer poUinia at all, or become hopelessly 

 entangled when they do." Occasionally pollen-masses are found 

 on the tongues of insects, especially on those of bees and wasps, 

 which move about with their unruly member sticking out. 

 Probably no one has ever made the e.xhaustive and absorbingly 

 interesting study of the milkweeds that Professor Robertson has. 



Better than any written description of the milkweed blossom's 

 mechanism is a simple experiment. If you have neither time nor 

 patience to sit in the hot sun, magnifying-glass in hand, and 

 watch for an unwary insect to get caught, take an ordinary house- 

 fly, and hold it by the wings so that it may claw at one of the 

 newly opened flowers from which no pollinia have been removed, 

 it tries frantically to hold on, and with a little direction it may be 

 led to catch its claws in the slots of the flower. Now pull it 

 gently away, and you will find a pair of saddle-bags slung over 

 "his foot by a slender curved stalk, if you are rarely skilful, you 

 may induce your fly to withdraw the pollinia from all five slots 

 on as many of his feet. And they are not to be thrown or scraped 

 off, let the fly try as hard as he pleases. You may now invite the 

 fly to take a walk on another flower in which he will probably 

 leave one or more pollinia in its stigmatic cavities. 



Dr. Kerner thought the milky juice in milkweed plants, 

 especially abundant in the uppermost leaves and stems, serves to 

 protect the flowers from useless crawling pilferers. He once 

 started a number of ants to climb up a milky stalk. When they 

 neared the summit, he noticed that at each movement the terminal 

 hooks of their feet cut through the tender epiderm, and from the 

 little clefts the milky juice began to flow, bedraggling their feet 

 and the hind part of their bodies. " The ants were much impeded 

 in their movements," he writes, "and in order to rid themselves 

 of the annoyance, drew their feet through their mouths. . . . 

 Their movements, however, which accompanied these efforts, 

 simply resulted in making fresh fissures and fresh discharges of 

 miiliy juice, so that the position of the ants became each moment 

 worse and worse. Many escaped by getting to the edge of a leaf 

 and dropping to the ground. Others tried this method of escape 

 too late, for the air soon hardened the milky juice into a tough 



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