CHAPTER VII. 

 MODE OF DISSECTING INSECTS. 



The External Anatomy. For this purpose alcoholic 

 specimens are necessary, the chief drawback being that the 

 alcohol causes the muscles to so contract that the joints of 

 the palpi and other appendages may be retracted; specimens 

 killed with cyanide of potassium and then placed in alcohol 

 may prevent contraction. With a lens mounted in a 

 holder, so that both hands can be used, the student can, 

 with a pair of fine forceps and a needle mounted in a handle, 

 remove the appendages of the mouth, the antennae and legs, 

 and with a pair of fine scissors cut off the wings. For ex- 

 amining microscopically the ends of the antennae and palpi 

 to discover the external parts of the sense-organs, the ap- 

 pendages should be carefully cleaned and then soaked in 

 eau dejavelle, or in dilute liquor potassa?, in order to render 

 the parts transparent. It should be borne in mind that the 

 liquor potassae dissolves the muscles, nerves, etc., leaving 

 only the external integument. The head with its append- 

 ages, the segments of the thorax, and the abdomen may in 

 most insects be dissected, the parts poisoned with corrosive 

 sublimate and gummed to a caul, in the manner represented 

 by Fig. 1. Dried beetles and other insects may be relaxed 

 by being placed overnight on wet sand, or placed in warm 

 water, in alcohol, or in glycerine. Hairy or scaly insects, 

 such as Lepidoptera, should be denuded with a stiff camel's- 

 hair brush: this of course is necessary in examining the head 

 of Lepidoptera. 



The Internal Anatomy. The dissection of the internal 

 organs of insects is exceedingly difficult and nice work, re- 

 quiring delicacy of manipulation and untiring patience. 



