PREPARATION OF INSECT SPIRACLES. 317 



Preparation of Insect Spiracles.* Mr. F. Dienelt remarks that in 

 most beetles the spiracles are found on the upper part of the abdomen. 

 The insect should be turned on its back and cut across the thorax 

 close to the abdomen; then turn again, and insert a sharp knife into 

 the opening made, and cut round the whole abdomen. As soon as 

 there is room, insert a small stick of soft wood sharpened to a flat 

 point, by means of which the object can be held securely while cut- 

 ting. All the cutting should be done on the lower side, so that a 

 margin is left on the upper part, which can be trimmed easily after 

 the object has become softened in liquor potassse. Steeping the in- 

 sect in this fluid for a couple of hours will destroy all the viscera. 

 Now hold the part down with a softened stick, which for this purpose 

 is far superior to mounting needles, and with a camel-hair pencil 

 remove the viscera and transfer the object to rain-water, removing 

 this two or three times to insure cleansing and to remove the last trace 

 of potash. Keep on brushing until it is certain that the object is clean, 

 and then trim the edges to suit before a final washing. If it be desired 

 to mount the tracheae in situ, greater care is necessary in treating, but 

 they show very well through the skin. Or, after most of the viscera 

 have been removed, the tracheae can be torn by a sawing motion with 

 the back of the knife from the spiracles and mounted separate. In 

 mounting larvae entire, they should be left in liquor potassae for a 

 longer time even a whole day without injury. In cleaning it is 

 necessary to keep them in the position in which they are to be mounted. 

 Larvae of the Lepidoptera show best when mounted on the side. In 

 preparing these, hold the larva under water with the pointed stick, 

 and clear out the viscera with a brush through the anal opening by a 

 rolling motion. After a start has been made the process takes but a 

 short time. Larvae will stand considerable pressure in cleaning, but 

 gentle manipulation of course answers best, especially in those cov- 

 ered with hair. It is best to commence with the largest beetles or 

 larvae one can find. Larvae too large to be mounted entire ought to 

 be opened along the back to give the liquor free access. 



Twenty-seven grains of potassa f usa to one ounce of water acts but 

 slowl on the chitiuous parts of insects, but very promptly on the 

 viscera. It is best kept in a paper-covered bottle, to exclude the light. 

 Mourn. Roy. Mic. Soc., August, 1887.) 



Mounting of Tracheae. Mr. F. T. Hazlewood dissects out the soft 

 parts and spreads them on a glass slide, letting them dry perfectly. 

 He then with a pencil-brush gives them a good coating of collodion, 

 after which he melts a little hard pure balsam in a test-tube and puts 

 it on the object with a cover-glass applied at once. The intestines, 



* The Microscope, vii. (1887) pp. 102-3. 



