1972] 
Mackay — Widow Spider 
239 
method. The runs were made on Schleicher cellulose acetate strips 
in a Shandon Electric cell, with a Vokam SAE 2761 power pack. 
Borate buffer (pH 8.48) was used and 150 V constant voltage at 
3 ma applied for several hours. The results to date indicate that 
there are differences, for example in the lowered mobility of the last 
band in geometricus (Fig. 10), but the method is too crude to permit 
accurate separation. 
A difference in the color of the extracted hemolymph was also 
noted : that from geometricus was pale pink and from rhodesiensis 
the hemolymph was colorless. 
Natural history The two species are found in the same habi- 
tat, often living within a meter of each other. No consistent differ- 
ences have been noticed in the position of the retreat or in the web 
structure. A qualitative examination of the prey remains of both 
species has failed to show food preferences. 
Differences have been seen in the breeding biology. The mean 
number of eggs per cocoon (in captivity) is different: 133.59 — 
39.78 (29 cocoons) for geometricus ; and 166.38 zb 70.31 (86 co- 
coons) for rhodesiensis. The diameter of the eggs is 0.91-0.92 mm in 
geometricus and 0.92-0.96 mm in rhodesiensis. The color of the egg is 
different: those of rhodesiensis are pale yellowish flesh; while eggs 
of geometricus are dark pink. Kaston (1970), however, has noted 
eggs of different colors in the same cocoons of black widows. The 
cocoons of both species are parasitized by the larvae of M antispa 
tenella (Neuroptera: Mantispidae) . No consistent differences were 
discerned in preliminary observations of the postembryological de- 
velopment. Two series of young of each species were reared to the 
sixth instar (adult males and immature females) and showed no 
differences in pattern. 
Latrodectus rhodesiensis sp.n. 
Figures 1-9 
Types Male holotype, female paratype from Salisbury (Rho- 
desia), deposited in the Natal Museum, Pietermaritzburg (South 
Africa). Paratypes deposited in the British Museum (Natural His- 
tory) and the Museum of Comparative Zoology. 
Description. Similar in appearance to L. geometricus. Females 
apparently have similar measurements. The male measures: 2.5 mm 
total length. Carapace 1.2 mm long and 1.0 mm wide. First femur, 
2.3 mm; patella and tibia, 2.6 mm; metatarsus, 2.6 mm; tarsus 1.0 
mm. Second patella and tibia, 1.4 mm; third, 0.9 mm; fourth, 1.7 
mm. 
