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. 



