ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 49 



labrum. (6 and 7) Upper and lower pairs of retractors and expanders 

 of the labella. (8) An upper pair acting in opposition to 6 and 7. 

 (9) Compressor of the end of each labellum. (10 and 11) Depressors 

 of labial and labral channels respectively. (12) Band uniting 

 apophysis of labrum to fulcrum. (13) Elevator and depressor of 

 palps. (14) Dilator of pharynx. (15) Opener of salivary duct 

 valve. 



The " pseudo-tracheae " of the labella appear to consist of a system 

 of tubes, each provided with a narrow longitudinal slit, through which 

 the saliva is rapidly spread over the surface of the labella, and which 

 by the capillary action caused by their narrowness produce adhesion 

 of the saliva to the surface ; the tactile hairs of the labella are con- 

 nected with nerve-endings ; and between the " pseudo-tracheae " are 

 sunk double chitinous cylinders entered by nerve-endings, and pro- 

 bably to be regarded as taste-organs ; a large salivary gland lies at 

 the base of the labella. With regard to the pumping arrangements 

 of the salivary glands and the sucking apparatus of the pharynx, the 

 author supports previous observers. Large air-receptacles are placed 

 in the fulcrum, labium, and head. 



Scent-Organ of Papilio.* — Mr. H. Skinner has observed that the 

 larvae of Papilio turnus and P. troilus, when irritated, project from a 

 slit in the prothoracic segment an orange-coloured bifid organ. The 

 apparatus is a scent-organ, and gives out a strong and disagreeable 

 odour perceptible at some distance, and seems to be designed to defend 

 the caterpillar from numerous enemies. 



The anatomy of the organ seems to have escaped investigation, as 

 most authors merely mention its existence, one describing it simply 

 as fleshy. It has the appearance of being a solid organ, but it is in 

 reality hollow throughout the entire extent, and of very thin texture, 

 tapering gradually to a point. It is drawn in by invagination, and is 

 protruded after the same method. If the larva be held so that 

 sunlight may pass through the extended organ, the progress of intus- 

 susception may be distinctly seen. 



Anatomy of Aphides. t — E. Witlaczil describes the fat-body of 

 the Aphides as being especially well developed in the abdomen, where 

 it forms a thick layer under the skin ; the large cells of this tissue 

 contain a number of fat-drops, present in such numbers as to render the 

 protoplasm and the nucleus scarcely recognizable in fresh specimens ; 

 the whole tissue has a spongy appearance. The fat-drops are often 

 coloured green or red, and frequently greatly affect the coloration of 

 the species. As in other insects, the musculature of the abdomen is 

 divisible into a motor and a respiratory group; from the stigmata 

 there pass up obliquely a group of two or three muscles, while a 

 second group passes towards the middle line, and another muscle, 

 attached a little behind the stigma, passes up backwards to the dorsal 

 surface. There are nine pairs of stigmata; from the first a well- 

 developed tracheal trunk proceeds forwards to supply the head, and 



* Proc. Acad. Nat. Sci. Philad., 1882, p. 239. 

 t Arbeit. Zool. Inst. Wien, iv. (1882) pp. 397-441 (2 pis.). 

 Ser. 2.— Vol. III. E 



