10 NEOTROPICAL PSELAPHIDAE 



will not allow a focus of the reverse side of the slide; a wooden slide carriei 

 can be used to advantage which will hold the inverted slide in place without 

 danger to the cover slip. 



When Euplectini are mounted in this manner, one is amazed at the de- 

 tail which has escaped observation of specimens on card points; the pores, 

 pubescence, foveae, sutures, and sensory areas take on a new significance. 

 However, the aspect and detail of depressions, grooves, or sulci are not well 

 shown in slide mounts, unless carefully stained while in the alcohol, and point 

 mounts are best for these and similar structural items. Therefore a combination 

 of alcoholics, triangle mounts, and slides is really necessary for complete 

 estimation of a specimen. 



Mouth-parts, antennal structure, eye facets, tarsi, and detail of genitalia 

 of the larger species are also best studied under slides; I have become con- 

 vinced that future taxonomy will come to depend on slide mounts for taxonomic 

 details between closely related forms, and to this end the micro-coleoptera 

 lend themselves admirably. 



Dark species can be bleached by hydrogen peroxide or Chlorox, and then 

 washed thoroughly in distilled water, dehydrated, and cleared as for the non- 

 bleached material. 



Where the end is the study of the comparative external morphology of 

 the pselaphids I have found it convenient first to rid the specimens of internal 

 tissue and the following technique has proved satisfactory: either old and 

 dry specimens or fresh material are placed in a cold potassium or sodium 

 hydroxide solution of between 15 per cent and 30 per cent for twenty-four 

 hours. The action can be hastened by placing them in 10 per cent hydroxide 

 solution and boiling for ten minutes. After this the specimens must be washed 

 thoroughly and then can be passed into 95 per cent alcohol directly, or the 

 integument can be stained with eosin, methyl orange, or acid fuchsin. After 

 dehydration the technique is the same as for regular slide mounts. These 

 potashed specimens can be still further cleared by passing them through the 

 bleaching fluids mentioned above. Such mounts show the endoskeleton with 

 great clarity, and are invaluable for study of minute details under oil im- 

 mersion at 1000 diameters or more. 



Genitalia. Specimens brought from the field in alcohol should always be 

 examined for extruded genitalia, especially the males. ^ Such material may be 

 treated differently, since the structure of the genitalia is hardly known in 

 Pselaphidae and comparative studies of these structures will undoubtedly be 

 valuable for a future, broader view of the taxonomy of the family as a whole. 



The extruded genitalia of the male should first be studied in situ to show 

 the relation of the pygidium to penis, orientation of the latter with respect to 

 dorsal, ventral, lateral surfaces, and whether the species belongs to the type 

 in which the pygidium hinges on one side, or whether to the group having the 

 pygidium of two pieces, a right and a left pygidial plate (in the latter case 



^ Or living material may be killed with carbon tetrachloride, followed by ether, as 

 suggested by Valentine (1934), or by ether alone, to initiate extrusion of aedeagus. 



