ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 197 



it probably helps to prevent the access of water to tbe tracheae, anl it 

 also assists tbe larvae in takiug advantage of surfice tension, enabling 

 them to hang by their tails from the surface, the body swinging freely 

 in the water while the stigmata are exposed to the air. 



Tbe fact that the author obtained specially clear preparations of the 

 tracheal system enabled him to make minute observations on the tracheal 

 capillaries. His conclusions, which he regards as true for insects in 

 general, are stated as follows : — The tracheal system consists of spiral 

 tracheae, with flattened epithelium, intima, and spiral threads, and of 

 tracheal capillaries, which are intracellular canals in the protoplasmic 

 outgrowths of the tracheal end-cells. These capillaries branch and 

 anastomose freely, forming the so-called capillary "network, but the 

 meshes of this network are in no way differentiated from the capillaries 

 themselves. According to the author, the respiratory interchange occurs 

 only in the capillaries ; the spiral tracheae are merely air-passages. 



In regard to the imaginal discs, the author notes several points not 

 hitherto observed by others, and especially emphasises their origin as 

 ingrowths of the hypodermis, and the absence of any relation to the 

 tracheal epithelium. 



Streblidse.* — Herr P. Speiser discusses this family of Diptera, para- 

 sites on bats, and probably derived from the Muscid stock. The forms 

 with five wing-veins are the most primitive, those with six or four are 

 more recent, those with reduced wings are youngest. Through Para- 

 dyschiria g. n., and Megistopoda there are in some features transitions 

 towards Nycteribidae. Two other new genera are established, Nycteri- 

 bosca and Lepopteryx, and a key is given to the known forms. 



Enemy of the Colorado Potato Beetle. f— Mr. C. E. Mead describes 

 the behaviour of a beetle, Collops bipunctatus, which devours the eggs 

 and larvae of the Colorado beetle. There is good reason to believe that 

 the main crop of potatoes in the vicinity (San Juan County, New Mexico) 

 is annually saved by the predaceous habits of C. bipunctatus. 



Mating in Moths, f — Mr. A. G. Mayer has made some interesting 

 observations and experiments on the mating instinct of Collosamia pro- 

 meth'a, which he hatched out and watched on Loggerhead Key, one of 

 the Dry Tortugas Islands, Florida. His general conclusions are the 

 following : — The male is positively chemotactic toward some substance 

 which emanates from the abdomen of the female, and which he perceives 

 through antennary olfactory organs. Females thirty to sixty hours old 

 are much more attractive to males than are young females five to ten 

 hours old. Virgin females are somewhat more attractive than are fer- 

 tilised ones of the same age. The male will mite at least four times, either 

 with the same or with different females. Neither males nor females pay 

 any attention to the coloration of their partners. The melanic colour 

 of the male has not been brought about by sexual selection on the part 

 of the female. 



Colour- Variation in Pupge.§— Mr. F. Merrifield, Prof. E. B. Poulton, 

 together with some other observers, have continued previous observations 



* Arch. Naturgesch., lxvi. (1900) pp. 31-70 (2 pis.). 



t Amer. Nat., xxxiii. (1S99) pp. 927-9. 1 Ann. Nat. Hist., v. (1900) pp. 183-90. 



§ Trans. Ent. Soc. Lond. ; 1899, pp. 369-433. 



