Epigynum structure

Sometimes the only way to tell similar-looking species apart is by the structure of the female reproductive organs, or as it is called in spiders, the epigynum. Here are a few drawings from Kaston's famous work featuring the epigynums of the 3 native black widow species.

First, is the drawing of an L. variolus:

(Notice the embolic sclerite left behind in each spermathecae)

Second, is the drawing of an L. mactans:

(Notice the difference in structure, and the single embolic sclerite)

Third, are some drawings of an L. hesperus:

(Notes: the first picture is of a virgin female, the second picture is of a mated female, the third picture is of a female that mated with at least 2 males. Interesting!!)

And just for kicks, here is a real picture of the epigynum of an L. hesperus:

Shown here is a cleared spermatheca (medial view) with a male embolus tip in the opening. The opening of the pointed end of the embolus tip rests at the most anterior inner wall of the spermatheca. Fertilization duct shown with a red arrow.

So, as you can see, epigynum structure is a very important factor in distinguishing species.

My next big project will hopefully be to get similar pictures for all 5 species in North America.