Miscellaneous. 865 one contained the egg sent with this paper, the other was a nest just finished, and contained no eggs. This bird is considered, 1 beheve, to be identical with the Enghsh Heron ; it most probably therefore lays four or five eggs, as Mr. Yarrell states that the English Heron does. The egg is a uniform sea-green colour, 2^ths in. in length, by 1 inch and rather more than ^ths in width. MISCELLANEOUS, On the Mode in which the Tachinse escape from their Pupa-cases and from closed situations in which they often occur. By Dr. Reissig. Amongst the phsenomena of insect-life few things are more re-markable than the power possessed by soft, newly-developed flies, such as the TachincBy of breaking not only out of the hard larva-skin, but also out of the closed situations in which these are generally found, as, for instance, from the galleries and pupa-cells of Saperda populnea and Cryptorhynchus lapathi in wood, of Tortrix resinana in resinous galls, &c. To explain this process it has often been supposed that the hard-ened larva-skin is softened by the insect when about to escape by means of fluid, or that the aperture was prepared by the larva before its change to the pupa state. The author however states, that according to his observations neither of these suppositions is correct; the margins of the aperture through which the fly escapes are evi-dently broken in a manner which could not be the case if the skin were softened by the agency of a fluid, and he was never able to detect any traces of a prepared means of exit. He has therefore come to the conclusion that the dried larva-skin is burst by the fly, and his observations have proved that this is done in the way which he describes as follows : — " The fly when about to escape can con-vert its head into a most wonderful apparatus, acting in the manner of a hydraulic press, and by this means not only burst its immediate envelope, but also overcome any obstacles which may lie in its way to the open air." His observations were made on the following species of Tachina : T. gilvay Hrtg., from Lophyrus pint ; T. pilipennis, Fall., from the resinous galls of Tortrix resinana ; T. Jlaviceps, Rtzbg., from the pupse of Noctuce ; T. fera, Linn., from the dried larva of Noctua piniperda, &c. ; but especially upon T. bitnaculata, Hrtg., from the cocoon of Lophyrus pini. His results are as follows : — In T. bimaculata he first observed that both at the moment of its escape and for some time subsequently the fly possesses the power of converting the head into a nearly perfect globe, the diameter of which is considerably greater than that of the body. The surface of the globe consists of the slightly translucent perga-mentaceous skin, which is folded together very beautifully in the TachincB from the eyes to the mouth, and this is extended to the form described by a thin fluid.
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