TECHNIQUES FOR THE STUDY OF 
SPIDER GENITALIA 
By Herbert W. Levi * 
Museum of Comparative Zoology 
In response to many inquiries, I want to describe the techniques 
used for studying genitalia in the spider family Theridiidae. These 
procedures are not original, but have been adapted from methods used 
by several colleagues and students. One technique used in the family 
Araneidae is new and, I hope, helpful to students of that family. 
I would like to urge strongly against making permanent microscopic 
slides of genitalia. Most slides are not permanent; even balsam may 
crystallize after fifty years. In dehydration, sclerotized parts may warp 
and, as the slide dries, the cover glass may crush anatomical struc- 
tures. The slides often become separated from the parts of the 
specimen kept in alcohol and are lost. However, mounting the geni- 
talia of common species on slides often saves time in their study. The 
medium found most useful is Hoyer’s fluid (Baker and Wharton). 
Luckily, most male spiders have two palpi. One, usually the left, 
is removed so that it can be turned to the desired angle. Palpi should 
always be examined completely submerged in 75 to 90% alcohol, 
never dry. Drying shrinks and distorts softer parts; partial submer- 
sion produces undesirable reflections. To prevent the parts from 
floating away in convection currents caused by the heat of the micro- 
scope light, the light is equipped with heat absorbing glass and 
the pedipalpus anchored in a piece of fibrous paper tissue at the 
bottom of the dish. Vaseline, sometimes recommended to keep the 
palpus in position, may cling to it, smear over it, and is difficult to 
remove. Examination is by binocular dissecting microscope, at magni- 
fications of 150 to 240 times. 
Small, translucent, weakly sclerotized palpi are common among 
theridiid spiders. A transfer to glycerine, after blotting off alcohol, 
may help to make visible the borders of transparent structures. A 
temporary slide mount in glycerine may be made; for examination 
under a compound or phase microscope. The palpus should always 
be returned to alcohol in a microvial (4X10 mm) stoppered with 
cotton, to be kept with the spider in a larger vial ( Fig. 1 ) . A per- 
manent mounting generally ruins the palpus for study, as sclerites 
become too transparent, may become distorted, and can not be turned 
* Manuscript received by the editor November 4, 1964 
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