106 



KNOWLEDGE 



[June 1, 1892. 



to the group. The Armadillo woodlouse must, by the 

 way, be distinguished from another common creature 

 which superficially resembles it, and which exhibits the 

 same peculiarity of rolling into a pill-like ball ; which 

 also is found in similar situations, and especially in the 

 wood of decaying tree-stumps. It is not, however, slate- 

 coloured, but of a deep shiny blacldsh brown, and the 

 minuteness and disposition of its legs, amongst other less 

 obvious characteristics, pronounce it a member of the 

 class Myriapoda, which contains the centipedes and milli- 

 pedes, instead of the class Crustacea. It is popularly 

 known as the pill millipede. To the woodlice, then, 

 which are Crustacea, and not to the millipedes, belongs 

 the milk-white Ants' companion above mentioned ; but, 

 though we have several species of woodlice in the 

 British Islands, and several of them remarkably common, 

 this is the only one that takes up its quarters in Ants" 

 nests. It is dignified with the extraordinary name 

 VJatyarthi-m Hofmansegaii. On lifting the stone which 

 covers a nest of the Yellow Ant, we may often see numbers 

 of these little creatures slowly crawling about, like little 

 white scales, very conspicuous by their clean and bright 

 appearance, which contrasts sharply with that of their 

 hosts. What their business in the nests is, remains a 

 mystery, and as the Ants take no more notice of them than 

 they do of the springtails above mentioned, it is evident 

 that they do not, like Clani/er, form a secretion agreeable 

 to their hosts ; but whatever the bond of association may 

 be, it seems to be one of long standing, for while other 

 woodlice have good eyes, Flnti/tn-t/inis has become blind, a 

 very natural result of living long in darkness, in the sub- 

 terranean galleries of the Ants. In this blind woodlouse 

 we see the same apparent compensation of senses as in 

 Clarujer, for the antenna, like those of the blind beetle, 

 are remarkably broad. These white woodlice do not 

 possess the power of rolling into a ball. They have been 

 found living in the nests of at least six different kinds of 

 Ants, and according to Sir .John Lubbock's observations, 

 when they were transferred from their native nests to 

 others previously unoccupied by the species, they were 

 received without molestation. 



We have now to notice what is perhaps the most 

 remarkable part of our whole subject, the association of 

 Ants with aphides or plant lice. The fondness of Ants 

 for sweets is at the bottom of this association. Aphides 

 secrete the sweet sticky fluid called honey-dew ; this. Ants 

 eagerly sip up, and this passion of theirs has led them to 

 the adoption of ingenious devices to ensure a constant 

 supply. This is, however, merely a general statement, 

 and must not be taken as implying either a uniformity of 

 procedure on the part of all Ants, or an identity of treat- 

 ment of all species of aphides ; in the details of their 

 relations, as in other matters, we see well illustrated the 

 variety of Nature. It is an oft-repeated observation that the 

 Garden Antclimbs shrubs and bushes in search of the aphides 

 that frequent twigs ; but one would not expect such species as 

 the Yellow Ant, for example, to do this ; their time is 

 chietiy spent below ground, and whatever aphides they 

 have to do with will be found either in or near their own 

 nests, and therefore on low plants. The tree-infesting 

 aphides have each a pair of minute tubes projecting from 

 the hinder part of the abdomen, and out of these issues the 

 glutinous secretion, while its flow is accelerated when the 

 Ants tap the body of the aphis with their antennae. Some 

 Ants get no farther than this ; such would live chiefly on 

 what they can get in their foraging expeditions, making 

 no provision in their own nests for a continuous supply of 

 food of any kind, subsisting, as it were, from hand to 

 mouth. Others, however, have reached a more ad- 



vanced stage ; conscious of the value of the aphides as 



yielding a continuous supply of an agreeable article of diet, 

 they in some cases build earthen sheds over them, as well 

 as protecting them by their own individual exertions from 

 the attacks of enemies. Others, again, have got still fai-ther 

 than this ; not satisfied with protecting the mature aphides, 

 they take care of the eggs also, keeping them in their nests 

 through the winter with provident sagacity, securing thus 

 the safety of their nest year's supplies. The observations 

 of Sir John Lubbock in this connection are very remark- 

 able. The Yellow Ant was again the species observed. 

 In a nest of these insects he found on one occasion in the 

 month of February some dark eggs, which were those of 

 the aphides ; when the nest was disturbed the Ants mani- 

 fested great anxiety over these eggs, and carried them down 

 into a place of safety. Some of these eggs he took home 

 and oft'ered to some of his own Ants ; they were immediately 

 recognised by the Ants and carried into the nest ; in about 

 a month's time they were hatched and yielded young 

 aphides. But now came a remarkable result ; the young 

 aphides, instead of stopping in the nest, a result that might 

 fairly have been expected to follow, either came out of their 

 own accord or were carried out by the Ants ; not finding 

 outside, however, such a food plant as they wanted, they soon 

 died. Some other experiments were equally unsuccessful, 

 but at length the truth of the matter was accidentally 

 discovered. In this last experiment there happened to be 

 near the nest some wild plants, such as usually grow near 

 Ants' nests, and when the aphides were hatched they were 

 taken by the Ants straight to this spot and placed on the 

 leaves. Then, shortly afterwards, others similar to these, 

 and either brought out by the Ants or of independent 

 origin, were found on a daisy plant near ; the Ants valued 

 them sufficiently to run up a wall of earth around them, 

 and thus the whole set continued flourishing throughout 

 the summer. In the autumn they laid eggs similar to 

 those that had been found in the Ants' nests. So the 

 secret was out. The Ants took charge of the eggs during 

 the winter, when they were of no use to them, but when, 

 if left outside, they would have been exposed to all the 

 vicissitudes and rigours of our Enghsh climate. When 

 spring arrived and the eggs hatched, and the insects were 

 becoming useful to their guardians, they were actually 

 carried out by these and placed on plants near the nest 

 where they could enjoy suitable food, and where also they 

 would be easily accessible to their owners, who to protect 

 their property proceeded to construct works and enclose 

 them in a suitable preserve. This certainly looks like very 

 marvellous intelligence. 



But besides these aphides which are supported on the 

 leaves of living plants outside the nests of the Yellow Ant, 

 several species are also habitually found inside the nests. 

 It is not altogether clear, however, what is the relation 

 between these aphides and the Ants. There is a whole 

 section of the tribe of aphides, which, instead of attacking 

 the leaves and young shoots of plants, live upon juices 

 obtained from their roots, and therefore necessarily dwell 

 under ground. They difi'er a good deal from the rest of 

 the tribe ; for example, no winged forms are known in 

 connection with them, and they are destitute of the two 

 tubes above referred to as honey taps, and their bodies are 

 covered with a waxy substance which exudes as a gummy 

 secretion from certain small openings on the back. This 

 substance seems intended to protect the insects from the 

 damp of the soil by which they are surrounded, as well as 

 to cover their eggs. Now, most species of this group are 

 found in Ants' nests, but since the loose sandy soil and the 

 warm situations chosen by the Ants are also just those that 

 suit the aphides, it does not foUow that the association is 



