DISSECTING THE BLOW-FLY. 17 1 



upon a strip of glass, covering with a thin square cover, 

 and severing with a sharp knife. If the insect has been 

 killed with chloroform, the organ will generally be found 

 protruding. Just a word en passant to encourage the 

 student to display his dissections naturally, in order to 

 give observers an idea of the real use of the various organs 

 in the insect economy. This cannot be better illustrated 

 than by reference to this proboscis, one of the late Mr. 

 Topping's favourite preparations. The more natural con- 

 dition should be mounted in glycerine, and though not so 

 pretty an object, is at least truthful. 



Put no insect to pain. Kill it at as early a stage in the 

 inquiry as is possible, either with chloroform, bruised laurel 

 leaves, or by means of the cyanide of potassium bottle now 

 so often used. 



Proceeding with the blow-fly, the wings may be detached 

 from the thorax by means of the knife, scissors, or forceps, 

 the legs taken off at the thigh, the halteres or poisers 

 detached, and the antennae cut from the head, completing 

 the list of appendages. The carcase must now be pinned 

 down in the trough, or fixed to the bedding by warm- 

 ing a spot with a hot iron, fixing the subject into the 

 melted stratum, and the integument carefully slit up with 

 a fine pair of scissors, upon both sides. The chitinous 

 skeleton must then be raised with the forceps, and the 

 attachments cleared away with the aid of a blunt needle 

 and a spear-headed instrument, when, if tolerably well per- 

 formed, the whole of the organs will be seen in situ. The 

 subject should now be left in a mixture of glycerine and 

 water (equal parts of each), for about twelve hours, after 

 which treatment the organs may be readily dissected. Dilute 

 alcohol is very useful when dissecting the nervous system 

 of insects. A more or less prolonged immersion hardens 

 the nerve fibre, which the student will find requires very 



