6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 94 



of the thorax. These four parts of the body are replaced in the KOH 

 and allowed to boil gently for about one minute. The elytra and 

 wings are transferred from the water to 95 percent alcohol for several 

 minutes and then mounted as described below. After boiling the body, 

 it is removed again to water, where the disintegrated viscera may be 

 pressed out and the antennae, mouthparts, legs, and genitalia dissected 

 ofif. If any of these parts (notably the head and thorax) are too heav- 

 ily pigmented to permit easy study with transmitted light they should 

 now be placed in a 3 percent solution of hydrogen peroxide to which 

 has been added a small amount of ammonia (about one drop per cm ^ 

 of peroxide). It is essential that fresh ammonia be used and that the 

 mixture be not allowed to stand before using. It quickly loses its 

 efficacy after being mixed. Two to six hours in this solution will 

 suffice to bleach the darkest sclerites, and this treatment has the great 

 advantage of leaving the edges and sutures darker than the rest. These 

 parts are now placed again in the boiling KOH for a few seconds to 

 remove the peroxide and are then returned to the water to remove 

 the KOH. Now all parts are transferred to alcohol for several minutes 

 and then mounted. The most satisfactory mounting medium known 

 to me is euparal. (This can be obtained at a considerably reduced 

 price under the name of Diaphane.) Specimens are arranged in a drop 

 of the medium on the slide and a cover glass gently pressed down 

 until all surplus medium is squeezed out. If necessary the cover 

 glass may be supported by means of paper rings, which prevent the 

 flattening and consequent distortion of the objects. The slides are then 

 labeled and dried for two or three days. 



Material prepared in this way has a few disadvantages. The parts 

 can be studied only in the position in which they are mounted. The 

 color and general shape or habitus of the insect is lost in large measure. 

 But these are much more than offset by the ease of examination under 

 the compound microscope and the fact that one can approach the ideal 

 of being able to see and use all of the characters that are actually 

 present on the body of the beetle. 



Illustrations 



The illustrations, which form an important part of this study, are 

 intended to serve primarily two purposes. First, they illustrate the 

 detailed anatomy of a typical staphylinid, together with that of other 

 special structures found only on other species ; and second, they il- 

 lustrate briefly the variations within the family of each of the struc- 

 tures treated. They have been prepared with these two aims in mind, 



