December 19, 1895] 



NATURE 



157 



The female ant, and apparently the Ornithobia, lay aside 

 their wings as soon as the eggs are fertilised. In adult 

 hemimetabolic insects the mouth-parts are either like 

 those of the larva, or not functional at all ; the form of 

 the body, the texture of the cuticle, the organs of sense, 

 and the legs are in general those of the larva, so that 

 we might consider the imago as merely a winged and 

 sexually mature larva. 



But the imago of the holometabolic insect is always 

 more than a winged and sexually mature larva. It differs 

 in the form of the body, in the internal anatomy, in the 

 organs of special sense, and usually in the structure of 

 the mouth-parts. Perhaps the smallest advance upon 

 the larva is seen in the imago of the Adephagous 

 Coleoptera, but even here, though the mouth-parts are 

 generally similar and the wings often rudimentary, the 

 -difference between the adult and the larva is much 

 greater than in a locust, cricket, or cockroach. Some 

 anatomical comparisons which I have made between the 

 larva and imago of the Carabida;, point to great changes 

 in the muscular system as sufficient to explain th • re- 

 tention of the resting-stage even in the absence of other 

 motives. The changes in the muscular system are 

 rendered necessary by extensive changes in the shape of 

 ; almost every segment and every appendage. But the 

 reason of these changes of shape is sometimes hard to 

 •discover. 



The greatest advantage won by holometabolic insects 

 is access to the pollen and honey of flowers. Both 

 flowers and insects benefit by mutual help, and have 

 become specially modified to make the most of it. Per- 

 haps no ametabolic insect regularly visits flowers. Some 

 ■small Hemiptera, which are hemimetabolic, do so, but 

 I believe that their visits have not called forth any 

 special adaptation on either side. The Coleoptera, 

 though holometabolic, have biting jaws, and this may 

 be the reason why so few of them regularly haunt flowers. 

 Hermann Miiller tells us that some tropical beetles have 

 the maxilke specially modified for honey-sucking. 



Three large orders of highly-organised insects contain 

 a greater or less number of honey-sucking species. These 

 are the Diptera, the Hymenoptera, and the Lepidoptera. 

 The honey-sucking Diptera are comparatively few, but 

 they are of importance to flowers, many of which depend 

 upon their visits for the fertilisation of their ovules. The 

 honey-sucking Hymenoptera are the bees. Of all in- 

 sects these make the greatest use of honey and pollen, 

 feeding upon it throughout life ; they exhibit a more 

 elaborate collecting apparatus, and have acted with more 

 effect upon the organisation of flowers than any other 

 insects. In Lepidoptera honey-sucking becomes more 

 frequent than in any other order. Every moth and 

 butterfly that feeds at all sucks honey, to pass over such 

 unimportant exceptions as the fruit-eating moths with 

 perforating proboscis. 



It is a striking proof of the importance of insects in 

 nature that they should have been able to call into 

 existence a profusion of beautiful flowers. All the flowers 

 of the garden and conservatory, all the wild flowers which 

 delight us by their perfume, colour, or form, are in a 

 sense the work of insects. What they found ready to 

 hand was a multitude of green or sober-tinted flowers 

 of small size, without honey or scent ; the visits of insects 

 have done all the rest. Flowers have done almost as 

 much for insects as insects have done for flowers. 

 Flowers are to innumerable tribes of insects all that 

 domestic animals and cultivated plants are to mankind. 

 Honey, which may be considered a joint product of the 

 flower and the insect, owes its great importance to three 

 properties. It is fluid, it is highly nutritious, and it can 

 be stored without undergoing putrefaction. Its fluidity 

 and concentration render it particularly suitable as a food 

 for those winged insects which lay their eggs singly or 

 a few together on scattered plants of one kind, and which 



NO. 1364, VOL. 53] 



must, therefore, spend much time in egg-laying, as well 

 as to those which spend much time in excavation or 

 building. Upon the fact that honey can be stored for 

 many months depends the whole domestic economy of 

 rnany species of bees and ants. The chemical possi- 

 bility of the conversion of honey into wax was a dis- 

 covery made by bees to the great advantage of their 

 architecture. Not only have special instincts been founded 

 upon the properties of honey, but its pursuit has led to 

 increased swiftness on the wing, keener perception of 

 colour and distance, as well as to obvious modifications 

 of mouth-parts and stomach. 



Like other facilities which encourage activity and in- 

 telligence in the adult, honey-sucking tends to arrest the 

 development of the larva. The parent undertakes all 

 responsibility and labour, and leaves the young with 

 nothing to do but to feed and grow. 



Honey-sucking is associated, but not rigidly or indis- 

 pensably, with the highest faculties ever attained by 

 insects. It marks, perhaps, the highest phase in their 

 evolution. No insect can get so high without passing 

 through a quiescent pupal stage, for without metamor- 

 phosis it cannot acquire organs of sufficient delicacy. 

 Those which attain to honey-sucking have within theix 

 reach all the accomplishments and all the civilisation of 

 which any insect is capable. 



To any one who considers the great importance of 

 honey in the life of the higher insects, it is a surprise 

 that ants should have climbed so high without honey- 

 sucking. They have biting jaws, and the workers have 

 no wings. Hence they are useless for the fertilisation of 

 flowers, and many flowers have developed elaborate 

 obstacles for the express purpose of excluding ants. 

 Ants, however, do supply themselves with honey in spite 

 of all obstacles. They will get it from Aphides if no 

 better way can be found. Some ants have learned to 

 store honey in subterranean receptacles, the most singular 

 of which are the enormously dilated crops of certain 

 individuals of the community, which sacrifice themselves 

 for the good of the rest, and are converted into enormous, 

 globular honey-pots. The Myrmecocystus of Mexico, 

 and the Caniponotus of Australia, furnish us with 

 examples.^ 



It would seem as if ants had sacrificed their wings for 

 the sake of carrying on their subterranean life with 

 greater ease. They have paid a heavy price for this 

 advantage, for loss of wings in the end involved exclusion 

 from flowers. The bees have managed to keep their 

 wings, and yet to build elaborate structures for the 

 family. 



Beginning with the Campodea form, insects have 

 ascended through several degrees of specialisation, 

 acquiring first wings, then complete metamorphosis, and 

 lastly attaining to honey-sucking. They have also de- 

 scended through equally marked stages, losing length of 

 limb first, then losing their limbs altogether, and in 

 extreme cases losing their heads and jaws almost com- 

 pletely. The highest perfection of the insect-type is 

 always found in the adult, the lowest degeneration in the 

 larva. To the intervention of the resting-stage is due a 

 singular relation between the two processes of evolution 

 and degeneration, which is, as far as I know, peculiar to 

 insects. In insects, as a general rule, the higher the 

 organisation of the adult, the lower the degeneration of 

 the larva. The complete metamorphosis of the Coleop- 

 tera, Lepidoptera, Hymenoptera and Diptera has 

 rendered it possible for their larvic to degenerate, and 

 yet recover in a later stage all that has been lost. The 

 grubs of the weevil and the bee would not have lost their 

 legs if the parent had been unable to provide them with 

 a store of food sufficient for the whole larval period, 

 which could be devoured without leaving the place of 

 hatching. The maggot would not have lost head and 



' Lubbock, "Ants, Bees, and Wasps," p. 19. 



