184 
Psyche 
[September 
Another variable, not yet investigated, is the different number 
of molts to adulthood of females. While Turnbull (i960, 1965) 
found that different amounts of food do not change the number of 
molts in Linyphia triangularis (Linyphiidae) and A gelenopsis potteri 
( Agelenidae) , it is known that the number of instars is variable in 
Nephila madagascarensis , examined by Bonnet (1930) and Gerhardt 
( 1 933 ) ? and in Latrodectus mac tans, studied by Deevey (1949). 
The spiderling molts once within the egg-sac. Herms et al. calcu- 
lated that spiders remain between 14 and 30 days in the egg-sac; 
Lawson calculated a minimum of 15 days, but usually 3 to 4 weeks. 
Probably the temperature determines the length of this period. The 
second instar includes only the period after emergence. According 
to Herms, females from California molt 6 to 8 times, males 3 to 
6. Blair reports that females from Alabama molt 6 times, males 5. 
Lawson found that in Kansas females undergo 7 to 8 molts, males 
4. Burt et al. reported 8 to 9 molts for Hawaiian females. Thorpe 
and Woodson recorded 6 to 9 molts for females and 3 to 6 for males. 
Deevey recorded that in southeastern Texas the females molt 7 to 
9 times, the males 4 to 8. Despite uniform conditions, in only one 
series did all the males and all the females from a single egg-sac 
mature at the same molt. All seven females fed maximally matured 
at the seventh molt. Deevey also recorded considerable variation in 
length of time to maturity. Latrodectus variolas and L. mactans 
may have been confused in some of these observations, although 
most probably apply to the much more common L. mactans. Unfor- 
tunately, it seems that none of the authors recorded differences in 
coloration of adults after different molts, although some poor photo- 
graphs show change in patterns. 
Deevey (1949), in a useful table, summarized the work of pre- 
Explanation of Plate 11 
Figures 10-19. Latrodectus mactans from Cuzco, Peru; coloration diagram- 
matic. Fig. 10. After hatching (males and females). Fig. 11. After first 
molt (males). Fig. 12. After second and third molts (male). Fig. 13. 
After fourth molt (adult male). Fig. 14. After third molt (female). Fig. 15. 
After fourth molt (female). Fig. 16. After fourth molt, variant coloration 
(female). Fig. 17. After fifth molt (female). Fig. 18. After sixth molt 
(mature female). Fig. 19. After sixth molt, variant pattern (mature fe- 
male). 
(Molts are counted from after leaving egg-sac; there is one molt within 
egg-sac.) 
White: white; crosshatch: light brown; double crosshatch; dark brown; 
light stipple: orange; dark stipple: red; black: black. There may be a 
yellow fringe around the red in areas marked white. 
