330 



SCIENCE-GOSSIP. 



[Oct. 1, 1865. 



SIMPLE OBJECTS.-VII. 



Dennedes and Pencil-tail. 



1. ViiimXA'dXiiPolyrenusldguruti). 



2. Dermestes. 



Both magnified ; figures below represent the natural size. 



DUllING the last few days of February and 

 livst fortnight in March may be obtained, 

 under the bark of aged ehn trees, two objects which 

 deserve a place in a inicroscopic cabinet, though, so 

 far as I have ascertained from dealers, they are not 

 commonly mounted. 



The first is the larva of a beetle— some sort of 

 Dermestes. It is of a light brown colour, and 

 covered with fine hairs, similar to those figured in 

 the " Micrographic Dictionary" as from Dermestes 

 Lardamis, but differing from the pictures of that 

 object in Carpenter's " Microscope and its Revela- 

 tions," and Hogg's work on the same subject. I 

 imagine this is because the specimens figured there 

 have been damaged in the preparation, perhaps in- 

 tentionally, with a view to show the structure. 



Being certain that many possessors of microscopes 

 have never seen the creature in its living state, I 

 venture to I'ecommend such persons as take a plea- 

 sure in preparing objects for themselves to make a 

 search for it. 



A low power, say ten diameters, is needed, and 

 opaque illumination. The Dermestes then looks 

 most formidable. It is covered with hairs of several 

 sorts, those of the halbut shape being the most 

 numerous, arranged close to the body, and pointing 

 from the sides to the centre of the back in the 

 anterior segments of the body, but grouped in small 

 bundles, each containing an infinite number of hairs 

 with.longer shafts than the others, and looking like 

 tiny sheaves of corn in the hinder segments. These 

 latter can be erected and spread out like fans, givmg 

 the creature somewhat of the porcupine appearance. 



There is also a bunch of long delicate hairs occu- 



pying the place of a tail, and the little fellow pro- 

 tests against interference by switching this article 

 sideways in a ludicrous manner, if touched. 



A preserved specimen can never give the full 

 beauty of the living animal; but partial success 

 may be gained by the following plan of mounting : — 



I procured a wooden slide, 3 in. by lin., and xs-in. 

 tliick, having a hole cut in the centre about f in. in 

 diameter. Having fastened to this a piece of clean 

 thin glass, I placed the insect in the cell thus 

 formed, and covered it up with another piece of thin 

 glass. By this means I can view both sides of the 

 creature without trouble, and also by illuminating 

 iVom above and below the stage simultaneously, 

 obtain certain advantages. 



The other creature which is worthy of a search is 

 obtained in similar situations. I have generally 

 found it, however, in rotten bark that is covered 

 with lichens and moss, while the Dermestes prefers 

 a more sheltered situation in the crevices between 

 the dead bark and the living wood.* 



Its popular name is "Pencil-tail" {Pohjrenits 

 lagurus\), so called from two silvery tufts of delicate 

 hairs which spring out of the hindmost segment. 

 These myriapods are often very numerous, and a 

 piece of the bark, having a colony of them upon it, 

 is a wonderfully beautiful sight under the microscope. 



They are grey, and their backs are covered by 

 transverse bands of curiously-shaped objects inter- 



«. h. Hau's of Dermestes. 

 c. d. Hairs of Pencil-tail. 

 All X 250. 



mediate between scales and hairs, of a leaden hue. 

 The sides and head are ornamented with bunches of 

 a similar character. 



To see these animals endeavouring to escape into 

 the dark crevices of the bark when the light is con- 

 densed upon them by means of the large bull's-eye, 

 cannot fail to excite surprise. 



* Sometimes I have found them iu company with each 

 other. t Wood's " Natural History." 



