EFFECTS. ()I• FLONVI:IIS IN NG I NsEcTs. Coining now to consider the mutual relations and dependence of insects and flowers, we will first take up the subject of the adaptation of insects to teething on the pollen or nectar of flowers. .1 few insects, sonic and certain caterpillars, may devour the petals of flowers: lint the chief attraction lies in the pollen or the nectar, and as the result we shall see that inseets visiting flowers for Clue purpose of feeding upon their floral products are remarkably modified for this purpose. Hermann has shown the way in which inseets are tilted to obtain their floral diet, how many eha•aelers of flowers and of their visitors "have been developed in reciproval adap tation. and width can therefore only be under stood when considered together." 'flue insects which feed on pollen or nectar, and the fertilize fleIwers. are certain bugs, beetles, flies, most moths and butterflies, wasps. and bees. It should be noticed that none of the primi tive. generalized. or net-veilwd insects are includ ed among these floral visitors. They contented themselves, as they do now, with the rank growth of herbaceous The true hug: (ardor lletnipteni) have the mouth-parts formed into a long beak adapted for piercing the flesh of or the leaves or stems of plants. But some of them (.1nthoeoris, ate.) are fitted by their small size to creep into and suck honey from many differe•t flowers. Alinnte insects of another group IThysanoptera) are (mist:nate found in flowers of all sorts. where• they feed both on milieu and honey. Midler they seize a single poll•n-grain in their jaw- and convey it to the mouth : they obtain honey by applying the mandibles and maxillae together so as to fora a short. conical sucking apparatus. Their jaws and accessory (maxillas) a re Luny and narrow, tapering to a sharp point, and here again we have long, slender, beak-like mouth parts adapted for probing flowers.
The modifications of the maxilke (jaws) of cer tain flower-visiting insects, adapting them in some cases for playing the part of butterflies and bees, are remarkable. Leaf-feeding beetles, such as chafers and chrysomelids, do much harm by de vouring petals or entire flowers, but there is no resulting modification. "A review," says Mtiller, "of the mode of life of insects which visit flowers, and of the families to which they belong, shows continuous gradations from those which never visit flowers to those which seek them as a sec ondary matter, and finally to those which en tirely depend upon them." In the great group
of longieorn beetles (Cerambyeidte), in which the head is generally short, the jaws are directed downward, so they can use them in biting the bark of trees in order to oviposit in it. There is a group (Lepturidx) which frequents flowers. These have the head lengthened out in front, a neck-like constriction behind the eyes, and con sequently the power to direct the mouth forward while the protbo•ax is elongated and narrowed in front; besides this, the lobes of each maxilla are furnished with a brush of hairs. All these departures from the normal type and customary habits are the result of a process of adaptation to a floral diet. Millen attributes this to natural selection, but one will readily perceive that this view is not practical nor adequate. There may be another point of view. As this type of beetles multiplied and ordinary food became scarce, com petition set in, necessities of existence drove the insects to the unusual diet of pollen and honey, and probably the body became modified as the re sult of constant effort in straining after the nec tar at the bottom of flowers, and the creature became long-necked, long-headed, and its tongue like maxilla especially adapted for brushing off and collecting grains of pollen. The case reminds one of the probable series of causes which led to the formation of the long neck and slender head and tongue of the giraffe.
Other beetles gather pollen, and their mouth appendages are adapted in accordance with this habit, while among certain families (e.g. Mon dellidte, (Edemerithe) all the species in a perfect state depend entirely on a floral diet. The most remarkable of all beetles adapted for sucking honey is the flower-visiting Nemognatha ( which means 'thread-like in which the galea of each maxilla is of enormous length, so that the two together form a rude sucking-tube, roughly comparable with the tongue of the butterflies. It is believed to be very sensitive, as it contains many taste-cups. here we see carried out almost to excess the idea of a tongue adapted for prob ing deep corollas. it is a ease of convergence, where the action of similar efforts and mechanical strains have gradually resulted in structures of the same form in insects belonging to entirely different orders.