Bugs, Cicadas, Aphids, and Scale-insects 175 



Weed as follows: "It winters over on the twigs in the egg state. Early 

 in spring the young aphids hatch and crawl upon the bursting buds, insert- 

 ing their tiny sap-sucking beaks into the tissues of the unfolding leaves. 

 In a week or ten days they become full-grown and begin giving birth to 

 young lice, that also soon develop and repeat the process, increasing very 

 rapidly. Most of the early spring forms are wingless, but during June 

 great numbers of the winged lice appear, and late in June or early in July 

 they generally leave the cherry, migrating to some other plant, although 

 we do not yet know what that plant is. Here they continue developing 

 throughout the summer, and in autumn a winged brood again appears and 

 migrates back to cherry. These migrants give birth to young that develop 

 into egg-laying females which deposit small, oval, shining black eggs upon 

 the twigs." 



The point of all this is plainly that in the aphids there must be recog- 

 nized an unusual and, to them, very advantageous adaptive plasticity of both 

 structure and function. Defenceless as are the aphid individuals as far 

 as capacity either to fight or to run away is concerned, the various aphid 

 species are, on the contrary, very well defended by their structural and physi- 

 ological plasticity and their extraordinary fecundity. 



The two secretions, wax and honey-dew, play an important part in the 

 aphid life. The wax secreted or excreted through various small openings 

 scattered over the body is, of course, liquid when first produced, but quickly 

 hardens ; the total waxy secretion appears usually as a mass of felted threads 

 or "wool," and doubtless is an important protection for the delicate body. 

 The honey-dew, long supposed to be secreted through two conspicuous 

 tubular processes on the dorsal surface of the posterior end of the abdomen, 

 is now known to be an excretion from the intestine, issuing in fine droplets 

 or even spray from the anal opening. From the so-called "honey-tubes" 

 issues another secretion, not sweetish, about which little is known. It is 

 common knowledge, however, that the aphid honey-dew is a favorite food 

 of ants the Germans call it the ants' "national dish" and many accounts 

 have been written of the care of plant-lice, the ants' cattle, by the ants them- 

 selves. Without question there is some basis of fact for these stories. No 

 more evidence of this is needed than the careful observations of Professor 

 Forbes of the extraordinary care of the corn-root louse by the little brown 

 ant, Lasius brunneus, of the Mississippi Valley corn-fields (see p. 545 for an 

 account of this). The feeding by ants on the fresh honey-dew can be readily 

 observed in almost any garden (Fig. 247), and undoubtedly the mere presence 

 in the aphid neighborhood of such redoubtable warriors as the ants is a 

 strong deterrent of various predaceous insect enemies of the plant-lice. 

 But most of the stories of ants and aphids printed in popular natural-history 

 books need to be tested by careful observation. 



