i82 NATURAL SCIENCE. Sept.. 



There are always two glands present, an acid and an alkaline. The 

 former may consist of a simple tube, of a bifid tube, of paired tubes, 

 or of a bundle of tubes. The epithelial coat of these consists of 

 several layers of cells. They open into a large oval or spherical 

 poison-reservoir, from which proceeds the duct to the sting. 

 The alkaline gland is a somewhat thick, irregular tube, whose 

 epithelial coat consists of but a single layer of cells, thrown into 

 folds ; its duct opens alongside that of the acid gland. A third, 

 accessory, gland is present in some cases. A remarkable fact 

 established by Mr. Bordas is that of the presence of these poison-glands 

 (or their homologues),not only in the stinging (aculeate) Hymenoptera 

 —wasps and bees, but also in the boring (terebrant) section of the 

 order — ichneumons, sunflies, etc. The exact function of the glands 

 in these latter insects, which do not sting, would be an interesting 

 subject for research. Mr. Bordas insists that the sting of aculeate 

 and the ovipositor of terebrant Hymenoptera are identical structures. 

 In the concluding part (just issued) of the work referred to above, 

 Mr. Lowne promulgates the same view, and expresses his opinion that 

 the egg is ejected through the basal part, at least, of the sting in 

 bees and wasps. 



In a former review (Nat. Sci., vol. iii., p. 446) I noticed 

 Professor Miall's description of a carnivorous crane-fly larva 

 {Dicmnota). The same naturalist, in conjunction with Mr. N. 

 Walker, has quite recently (7) given descriptions and figures of the 

 larva and pupa of Pericoma canescens, another two- winged fly, but 

 ■belonging to the family Psychodidse. The very small, hairy flies of 

 this family may often be observed on window-panes, and the larvae 

 described were found in a paved water-channel and on the banks of 

 muddy ponds. The grub can live either in water or air, and feeds on 

 freshwater algae. It breathes air by means of two spiracles situated 

 at the end of paired processes, one on either side of the second body- 

 segment (mesothoracic) ; and two other spiracles at the extreme 

 hinder end of the body. The hindmost segment, on which these 

 latter open, bears four processes, each provided with a number of 

 filaments set with very fine hairs. These feather-like structures act 

 as a cup which encloses air, so that the grub, which " seems most at 

 home in water just deep enough to cover the body," can feed with its 

 mouth at the bottom, while its tail is at the surface. If entirely sub- 

 merged, as by a sudden flood, the feathery processes enclose a bubble 

 of air, which will serve for respiration for a considerable time, the 

 spiracles being kept dry. When full-grown, the larva leaves the 

 water, and the pupal stage is passed by the insect, buried in the 

 earth or beneath a stone. The pupa breathes by means of a pair of 

 respiratory trumpets on the prothorax. The value of this paper is 

 increased by an appendix, due to Baron Osten Sacken, giving an 

 account of all the literature relating to the development of Psycho- 

 didae. The latest memoir quoted herein is a description, by Dr. F. 



