Mating System: monogamous
Copulation among Latrodectus mactans is unique. A mature male spins a small “sperm web” and deposits a small quantity of semen on it. He then charges his palps with the sperm, abandons his habitat, and spends considerable effort to locate a female of his species. Once the female black widow spider has been located, courtship begins. The male vibrates the threads of the female’s snare to be sure she is the right species, for her to recognize him as a mate, and to make her receptive to mating. Mating takes place when the male inserts his papal organs into the spermathecal openings of the female. The spermatozoa are released onto the eggs. The eggs are laid onto a small web and are covered with more silk until they are completely surrounded by an egg sac or cocoon. This egg saw is then camouflaged, guarded, or carried by the female. Within the egg sac, the eggs hatch and spiderlings (juveniles) emerge. The female black widow spider’s egg sac is pear-shaped. In addition, the female Latrodectus mactans can store a lifetime supply of sperm to fertilize all the eggs she will ever produce. (Hillyard, 1994; Snow, 1970; Kaston, 1953; Wallace et al, 1991; Foelix, 1996)
Breeding season: spring
Range number of offspring: 10 to 917.
Range gestation period: 8 to 30 days.
Average gestation period: 20 days.
Range : 2 to 6 months.
Average : 3 months.
Range age at sexual or reproductive maturity (female): 70 to 90 days.
Range age at sexual or reproductive maturity (male): 70 to 90 days.
Key Reproductive Features: seasonal breeding ; sexual ; fertilization (Internal ); sperm-storing
The female rarely leaves the web. She watches over the eggs in the egg sac until the spiderlings hatch. The spiderlings disperse soon after hatching, at which time parental care ceases and the spiderlings must fend for themselves.
Parental Investment: no parental involvement; female parental care