Mexican red-knee tarantulas mate shortly after the male's maturing molt. Before copulation, males weave a special web on which he deposits sperm. Mating occurs near the female's burrow. The male and female face each other, and the female opens her jaws wide. The male uses a special pair of spurs on his front legs to lock her jaws open. They then push each other into a reared-back position. With second set of legs, the male holds the female down and bends her backwards. The male then collects his sperm with his pedipalps and transfers it to the female's opithosoma, a small opening on the underside of the abdomen. The male releases one of the female's fangs, positioning hims legs for retreat. After mating, males generally flee, as females are known to be aggressive to males after mating. Some females may try to kill and eat the male, although this has not been observed in the wild. Mexican red-knee tarantulas are polygynandrous.
Mating System: polygynandrous (promiscuous)
Mexican red-knee tarantulas mate soon after the male's maturing molt, which usually happens between July and October during the rainy season. Females store the sperm and eggs in her body until the spring. Females make a silk mat, on which she lays 200 to 400 eggs, which she covers with a sticky liquid containing the sperm. Fertilization occurs in minutes. The eggs are wrapped in silk and collected into a ball or egg-sac. Females carry the egg-sac between their fangs. Eggs hatch in 1 to 3 months, though spiderlings remain in the egg-sac for another 3 weeks after hatching. After leaving the egg-sac, spiderlings spend another 2 weeks in their burrow before they disperse. They reach independence at this point, usually at 12 to 16 days of age. Males reach sexual maturity at approximately the 20th instar (the stage between molts that comes at about 4 years of age). Females mature 2 to 3 years later than males, at 6 to 7 years of age. In captivity, Mexican red-knee tarantulas mature more quickly than in the wild.
Breeding season: Mexican red-knee tarantulas typically mate between July and October, usually in the rainy season.
Range number of offspring: 200 to 400.
Average gestation period: 9 weeks.
Range time to independence: 12 to 16 days.
Range age at sexual or reproductive maturity (female): 6 to 7 years.
Average age at sexual or reproductive maturity (male): 4 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Female Mexican red-knee tarantulas wrap their eggs in a silk egg-sac and carry them between their fangs. Egg-sacs may also be placed in hollows between or beneath rocks or natural debris. A female guards her egg-sac, turns it, and moves it around to ensure appropriate humidity and temperature are maintained. Eggs hatch in approximately 9 weeks, though spiderlings remain in the egg-sac for another 3 weeks. After emerging from the egg-sac, they remain in the burrow with their mother for an additional 2 weeks. Mothers guard their offspring until they disperse around 12 to 16 days of age.
Parental Investment: precocial ; female parental care ; pre-hatching/birth (Protecting: Female); pre-independence (Protecting: Female)
- Jacksonville Zoo & Gardens. 2008. "Bio Facts: Red Kneed Tarantula" (On-line). Jacksonville Zoo. Accessed November 10, 2009 at http://www.jaxzoo.org/animals/biofacts/RedkneedTarantula.asp.
- Moya-Larano, J., J. Pascual, . Wise. 2003. Mating patterns in late-maturing female Mediterranean tarantulas may reflect the costs and benefits of sexual cannibalism. Animal Behaviour, 66(3): 469-476. Accessed November 11, 2009 at http://www.uic.edu/depts/ovcr/iesp/Publications/Faculty%20Publications/Wise/Moya-Larano%20J%20et%20al%202003%20Anim%20Behav_Mating%20Patterns.pdf.
- Oakland Zoo. 2008. "Mexican Red Knee Tarantula" (On-line). Oakland Zoo. Accessed November 10, 2009 at http://www.oaklandzoo.org/animals/arthropods/mexican-red-knee-tarantula.
- West, R. 2009. "Mexican Red Kneed Tarantula" (On-line). Arkive. Accessed November 10, 2009 at http://www.arkive.org/mexican-redknee-tarantula/brachypelma-smithi/info.html.