ANTS AND APHIDS 



The Remarkable Relations Existing between Them — Aphids Act as "Cows" for 

 the Ants, in Return for Care and Protection — A Baffling Problem of Heredity 



OF ALMOST fifteen hundred in- 

 sects, spiders and crustaceans 

 who have unusual amicable re- 

 lations with the ants or who live 

 in the same nest with them, none is of 

 more interest than the comm.on aphis. 

 Mealy bugs, tree hoppers, lantern flies, 

 and certain species of caterpillars also 

 live in the same relationship, but the 

 relationship in the case of the aphis 

 is most apparent. 



Aphids live on practically every 

 form of plant life and on every part of 

 the plant, including the roots, stems 

 and leaves. They pierce the integu- 

 ment of the plant with their hard and 

 sharp mouth-parts and suck the juices, 

 which consist of water, cane sugar, in- 

 vert sugar and possibly a slight amount 

 of albuminoid matter. 



The juices pass through the alimen- 

 tary canal of the insect, where a slight 

 portion is absorbed, the rest under- 

 going a chemical change wherein the 

 cane sugar is turned to invert sugar or 

 glucose. The changed plant juices are 

 then voided through the anal opening 

 in the form of colorless droplets. 



Reaumur in 1737 and Leche in 1765 

 were the first to ascertain the true 

 origin of these droplets, which often 

 collect on the leaves in vast quanti- 

 ties. The linden aphis was found by 

 Biisgen (1891) to void nineteen drops in 

 the course of twenty-four hours, while 

 the maple aphis excreted as many as 

 corty-eight drops in the same time. 

 This is a surprisingly large quantity 

 considering the small size of the insects. 

 This voiding of "honey dew" fur- 

 ishes the ant with a never failing supply 

 of nutritious and, to it, delightful food. 

 Some species merely lick the leaves on 

 which the dew has dropped, others do 

 not appear to hunt for the liquid at all, 

 but most ants learn to stroke the aphids 

 in order to make them void the sought- 

 for food, just as a cow is induced by the 



hired man to "give down" milk. Thus 

 the honey dew can be imbibed directly. 

 Some ants are found to live exclusively 

 in this manner. 



THE ants' procedure 



When desiring food, the ani caresses 

 the abdomen of the aphis with first one 

 and then the other antenna. The 

 aphis immediately voids a droplet of 

 honey dew, which is at once seized by 

 the ant, who goes on to another aphis 

 and repeats the operation. If the 

 second aphis fails to respond the ant 

 perceives that nothing is to be expected, 

 since the aphis has no honey dew left 

 at that moment, and goes on to another. 

 Five or six such repasts are sufficient 

 to satiate the ant, and she returns to 

 the nest. If the aphis does not receive 

 sufficient attention from the ants, it 

 voids the droplet without waiting to 

 be stroked. In this case, the droplet 

 is ejected forcibly some distance, which 

 is not the case when it is given directly 

 to the ants after stimulus. 



The ants sometimes exhaust the 

 aphis' supply of honey dew and then 

 have to wait until the aphis can pump 

 up a fresh supply from the plant. The 

 aphis is very generous, however, and 

 will often yield several droplets in 

 succession to different ants. 



Some aphids have on the sixth ab- 

 dominal segment a pair of tubules, and 

 it was the idea for a long time that 

 these were the source of the honey dew. 

 This has now been proved false. The 

 excretion of the tubules is yellow and 

 sticky and is used as a protection 

 against the lady-bird beetle, the so- 

 called aphis-lion, and other hereditary 

 enemies of the aphis. When the enemy 

 attempts to seize the aphis, the latter 

 immediately excretes the defensive 

 liquid from the tubules, smearing the 

 head and thorax of the beetle with it. 

 This usually frightens, blinds or dis- 



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