(Cerceris, Fig. 3) in seeking out and capturing the pretty beetles of the genus Buprestis, which he had great difficulty in finding himself. In making a study of these beetles he collected the material from the burrows of Cerceris, and so avoided the laborious task of obtaining

them in the natural state of freedom. The burrows were filled with motionless, but perfectly well preserved, Buprestes. Although dead Coleoptera dried up in a short time, those recovered from the burrows remained in a good state of preservation for weeks. Léon Dufour came to the conclusion that the Cerceris kill their prey, but inject into them some antiseptic liquid which perfectly preserves their flesh and intestines.

J. H. Fabre pursued the study of the habits of fossorial wasps further. He ascertained that the captured insects were not dead, but only paralysed. The continuance of the function of certain organs demonstrated that the Buprestes, the weevils and other small creatures collected in the burrows of fossorial wasps, were alive. They could even perform some slight movements, but they were incapable of locomotion, and so could not escape. The mechanism of this paralysis, as far as could be ascertained by Fabre, is one of the most remarkable phenomena in nature. The fossorial wasps, guided by their instinct, immediately after having seized an insect or spider, bury their sting in the nervous centre which controls the movements of the legs. When animals with soft bodies, such as spiders and young crickets, are attacked, the operation does not present any difficulties. But Coleoptera in general, and the Buprestes

and weevils in particular, are furnished with a very hard covering which cannot be perforated by the small and slender sting of a fossorial wasp. To gain their object the wasps probe exactly between the first and second pair of legs in the median line of the under surface of the thorax. The skin is thinner at this spot, and they introduce their sting into the ganglia from which arise the nerves of the legs. In the case with the Buprestes these ganglia are set close to one another, and a single prick suffices to affect the nervous centres of three pairs of legs: Once the sting has been inserted in this way the Buprestis becomes paralysed, but lives for many days. "The Cerceris which preys on Coleoptera," writes Fabre,* appears to have made its choice according to the dictates of an exact physiology and anatomy. It is impossible to see in its proceedings the results of happy chance; more than chance is required to explain adaptations so precise."

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After having filled the burrow with a sufficient quantity of insects or spiders, fossorial wasps lay their eggs and carefully close up the entrance. In due course the larva is hatched, and devours the food that it finds close at hand. If the gathered insects were not paralysed, they could easily escape from their prison; if they were dead, putrefaction or desiccation (according to circumstances) would render them unfit for the larvæ. It is therefore sheer necessity that is the factor in the development of this marvellous instinct that induces the fossorial wasps. to attack the nervous centres of their prey. When one insect has been devoured, the larva proceeds to another, and so on, until it is fully grown, whereupon it envelops itself in a case that protects it during the winter and Fabre, "Souvenirs entomologiques," vol. I., pp. 71-78, Paris,

1879.

following spring. In summer it changes at first into a chrysalis, and later into a perfect insect. It frees itself from the cocoon, takes to flight, and enters upon life like that of its mother, which it has never seen.

Of the harmonious phenomena in nature it is indeed difficult to find other examples so perfect as those of the habits of these fossorial wasps, or of the mechanism for the fertilisation of orchids. These harmonies in nature are constantly met with in the world of living beings, and it is not astonishing that they have for a long time attracted the attention of many observers and philosophers. As it seemed impossible to attribute them to the organisms themselves, because of the low rank and lack of intelligence of these, it has seemed only natural to set them down as a manifestation of a superior force which organises and directs all natural phenomena. This argument, however, omits one side of the medal.

Any close investigation of organisation and life reveals that, beside many most perfect harmonies, there are facts which prove the existence of incomplete harmony or even absolute disharmony. The examination of the flowers of orchids would lead one to the belief that each part, even the smallest and apparently most insignificant, has its role in the mechanism for fertilisation and cross-fertilisation. In reality it is not so. There are in certain orchids organs which do not fulfil any function.

Even among the species of Catasetum, in which the pollinia are thrown with force on the bodies of insects, there are some female flowers in which the male organs are rudimentary and without utility. In these flowers, according to Darwin,* "the two membranous sacks containing the rudimentary pollen-masses never open, but they easily *Loc. cit. p. 201.

separate from each other and from the anther. The tissue of which they are formed is thick and pulpy. Like most rudimentary parts, the pollen-masses vary much in size and form; they are only about one-tenth of the bulk of those of the male." There are then, without doubt, some structures that are of no service.

The existence of these rudimentary pollinia, incapable of being transported or of fertilising the female element, is easily explained by the supposition that formerly the flowers of the Catasetum were true hermaphrodites, but that in the course of time the male organs have become incompletely atrophied in certain flowers, in which, on the other hand, the female part has increased. The occurrence of an actual degeneration is shown by the existence of rudiments of the pollinia too insignificant to accomplish their normal functions.

Rudimentary and useless organs are widely distributed, and we find them in many places. Familiar instances are the atrophied eyes of animals that live in the dark, and the sometimes rudimentary sexual organs of many plants and animals.

Not only are orchids and other flowers adapted to fertilisation by means of insects, but many insects display special adaptations to their habit of visiting flowers. Butterflies, bees, and many other insects, possess mouth organs modified for the purpose of penetrating flowers to secure nectar or pollen. Other insects, again, are not so fortunate. in this respect. Darwin * on one occasion "found an extremely minute Hymenopterous insect vainly struggling to escape, with its head cemented by the hardened viscid matter to the crest of the rostellum and to the tips of the pollinia (of an orchid, Listera ovata, Fig. 4). The insect

* Loc. cit. pp. 120-121.

was not so large as one of the pollinia, and after causing the explosion had not strength enough to remove them; it was punished for attempting a work beyond its strength, and perished miserably."

Many insects, well adapted for the purpose, delight themselves by sucking the nectar of flowers. Many others would wish to do the same, but their want of adaptation baffles them. A small "lady-bird" loves the sweet juice of flowers; it tries often to suck the nectar of the dandelion, but without success. Hermann Müller * has described the behaviour of this insect in procuring the nectar of Erodium cicutorium. "The awkward way in which this beetle, unadapted to feed on the plants, endeavours to obtain the honey, is too ludicrous not to be mentioned. After taking up a position on the petal, it puts its mouth in the direction of one of the honeycups which are situated on both sides of the base of the petal. The petal soon breaks off, upon which the insect fixes itself on a neighbouring sepal or falls to the ground with the petal. In the first case it proceeds to creep over the flower and ends by detaching all the petals; in the other case, on recovering from the shock, it quickly ascends another stem of the same plant and begins again. I have seen the same lady-bird fall four times in

* "Die Befruchtung der Blumen durch Insekten," p. 167, 1873.