Page:Hardwicke's Science-Gossip - Volume 1.pdf/92

76 all insects with the power of flight, and consequently in the Pieris, this apparatus develops a pair of pouches destined to contain air, and thus, of course, diminishes the speciic gravity of the body. According to Newport, it is only in the chrysalis that these organs are formed with rapidity. In Pieris, they first appear some time in autumn, and are half-formed before the winter; they remain at a standstill during the season, and assume their perfect form a short time after the last metamorphosis.

The function of all the organs we have already described is that of preserving or maintaining the life of the individual. They are all, moreover, in the full exercise of their duties from the moment that the creature emerges from the egg. Those organs connected with the perpetuation of the species are very differently situate. These are so slightly developed, and so imperceptible whilst the insect is in the caterpillar stage, that the penetrating researches of Herold could not demonstrate their existence. These organs are quite rudimentary, even at a period of five months after the conversion of the caterpillar into a chrysalis. It is only at the last moment, and just as the butterfly is about to make its escape, that they are to be seen in process of completion, whilst they undergo their entire development only in the perfect insect.

Here we must notice a very significant fact, and one which bears forcibly on the present subject. The female Pieris dies soon after depositing her eggs, and the male ceases to exist at a still earlier period. Matrimony is as fatal to them as it is to all insects, and their existence terminates when the preservation of the species has been insured. There is, however, an occasional circumstance which, by preventing the discharge of the functions essential to this final object, prolongs the usually short life of these insects to an extent beyond that which is intended. Some butterflies do not emerge from the chrysalis case till late in autumn, and then the cold tempurature of the surrounding atmosphere retards their development, and winter comes on ere they have begun their amours.

In consequence of this, they retire to some sheltered spot, remain there during the whole season, and reappear in spring. Thanks to this condition of celibacy, the result rather of circumstances than of desire, their lives, instead of being limited to a few weeks, extend over several months.

(Anthus spinoletta L.)

HE first intimation of the occurrence of this Continental bird in the British Isles, or at least the first which was made public, was the exhibition at a meeting of the Zoological Society, on January 24th, 1865, of a specimen from the collection of the Bishop of Oxford, stated to have been obtained near Brighton, in the winter of 1859-60 (see p. 64). From information afterwards received, we were led to correspond with the Rev. Tristram on the subject, and as the name of this gentleman is well known to British zoologists, his communication will be accepted with confidence. He writes:—

"I have no hesitation in stating that I can distinguish no difference between a pair (male and female) shot by me in January, 1861, on the island of Rorkahill, on the east coast of Ireland, and specimens I have obtained in Greece, Tunis, and Cyprus. In this I am borne out by my friend, Mr. A. Newton. The common Northumbrian species is A. obscurus, and I never heard of A. spinoletta on our modern coast."

Upon such authority, therefore, we can no longer object to recognize the Water Pipit amongst our occasional visitors.

This Pipit, during the breeding season and summer, appears to be an inhabitant of the Swiss Alps, the Tyrol, the Pyrenees, and other mountainous districts; but in the autumn and winter it descends to the plains, and is found along the course of rivers. It is probably to be met with at this season on both shores of the Mediterranean, and in some of the Mediterranean Islands. In the north of Europe it is rarely found, being confined chiefly to the south and west. This is not the place to enter upon the question of its identity with at least a closely allied American species. Our species most resembling it is the Rock Pipit (Anthus obscurus). From this it differs chiefly in the following particulars:—In the Rock Pipit the beak is of a dusky colour, yellowish at the base, and the legs and feet reddish-brown. In the Water Pipit the beak, legs, and feet are black. In the Rock Pipit, the primaries, or longer and outer wing feathers, have the outer feather the longest, and the three next successively shorter. In the Water Pipit the first four primaries are of nearly equal length, but the third is slightly the longest, and the first the shortest. In the Rock Pipit those wing-feathers, which are termed the wing-coverts, are dusky, edged with pale olive, but not very distinctly, and in the Water Pipit they are bordered with yellowish, so as to form two bands across the wings. Any more minute description would only interesting to the scientific ornithologist.

Having pointed out the most prominent features whereby an ordinary observer may discover to which of the two species any stray visitor may belong that may find its way into his hands, we wait with patience for further confirmation of its claims to be included in the British Fauna.