1967] 
Pinter — Widow Spiders 
293 
to non-melanin pigments, no attempt was made to identify the pig- 
ments. They are assumed to be ommochromes. 
With the use of an ocular micrometer, accurate to 0.1 mm, 
measurements were made of 34 morphological features. These meas- 
urements were selected because the margins of the structures were 
readily determined, thus permitting precise measurements which can 
be duplicated. The measurements taken between the eyes were not 
used because there were no significant differences between the individ- 
ual species. Some ratios obtained from the remaining values are 
illustrated (Fig. 25) and discussed. 
Using the dissecting techniques described by Levi (1965), I re- 
moved the epigyna from the specimens and exposed the internal geni- 
talia by removing associated tissue and clearing the ducts in clove 
oil. Illustrations were made of the seminal receptacle, and the ex- 
ternal and internal duct spirals (according to de Biasi, 1962). 
RESULTS 
Abdominal markings. A variety of ventral markings are shown in 
Figures 1-19. 
The vertical columns of venter patterns illustrate some of those 
observed in each of the populations. 
In population No. 1, the yellow pattern had a shield-like appear- 
ance. There were two specimens with complete shields which filled 
the ventral area (Fig. 2) and a few specimens had shields with in- 
dentations along the anterior or lateral margin (Figs. 3, 4 & 5), 
but the majority of the shields had only a faint black indentation along 
the anterior border (Fig. 1). With no exception among 83 speci- 
mens, the shield extended from the margin of the epigastric furrow 
to the base of the spinnerets ; whereas, there were no examples of this 
feature among the specimens from the other three populations. 
In population No. 2 a slightly different pattern emerged. Whereas 
the pattern did not extend posteriorly to the spinnerets, the entire 
anterior margin of the square was in contiguity at the epigastric 
furrow on all (136) specimens. Figures 6 through 10 show five 
variations of the basic square pattern; a majority of the patterns 
were similar to that shown in fig. 8. In studying a much larger 
EXPLANATION OF PLATE 36 
Figs. 1-19. Abdominal Markings. Diagrammatic illustrations showing 
the ventral abdominal patterns, including the epigastric furrow (e) and 
spinnerets (s) ; booklungs, epigyna, and lateral extensions of the dorsal 
pattern are not shown. 1-5. Latrodectus No. 1. 6-10. Latrodectus No. 2. 
11-15. Latrodectus No. 3. 16-19. Latrodectus No. 4, 
