Phidippus clarus

Phidippus clarus becomes adult in early summer,[7]^: 278 and females about to lay eggs can weigh 400 milligrams (0.014 oz).[7]^: 278[7]^: 12–13 Early in the breeding season, in early to mid-July, there are more males than females. The females all become sexually mature at the same time. At this point of the breeding season males die off, so that the number of males becomes equal to or slightly smaller than the number of females.[6] By August, most females live in their nests overnight for increasing periods, as this is where they will lay eggs.[1] The nests are located in rolled up leaves[14] and are made of thick silk, which is expensive to build. The egg sacs are conspicuous, as they are made of such thick silk.[5] Tests show that females use visual landmarks to return to their nests. A male only remains at the same nest when paired with a female.[1]

Like other spiders and many other arthropods, P. clarus can vibrate surfaces to interact with others of its species, sometimes in conjunction with other communications such as movements, to intimidate rivals and woo mates.[6]

One mated female P. clarus can lay well over 100 eggs per sac in a thick silken cocoon.[4]^: 52 An average clutch contains 135 eggs.[5] Most females bear only one clutch of eggs,[11]^{: 136–137} but some lay more.[1] The females stay with the egg cocoon and usually die a few days after the spiderlings leave the nest.[11]^{: 136–137}

The egg membrane is shed in 24–26 days, but the hatchlings (the first instar) continue to mature in the cocoon. The first molt occurs 24–28 days after the membrane is shed, and two to three days later the spiderlings leave their protective cover and become active, independent individuals. They do not hunt immediately, even if prey is available, but spend several hours engaged in apparently random activity before seeking cover, where they remain between two hours and two days. About 10% of spiderlings build retreats during this period, while the rest do so only after they have fed.[4]^: 52 The mothers usually die a few days after the spiderlings leave the nest.[11]^{: 136–137}

Competitions between P. clarus males occur on leaves up to 5 cm (2.0 in) long and wide, and the prize is the right to cohabit in the nest of a sub-adult female who is about enter her last molt and become fertile.[15] Initially, the contending males use vibration and visual displays, and the number of vibration signals often determines which male wins.[6] Males may use "leg-fencing", trying to push each other backwards with their front legs and bodies. Some of these contests escalate to grappling, in which males lock chelicerae (jaws) and legs for relatively longer periods.[15] In contests, males with previous experience of winning are more likely to win later contests, and males with more experience of losing are more likely to lose in future. In both winners and losers, more recent experience is more important than earlier experience. However, the weights of the contenders has the most influence, and experience makes a difference only between individuals of similar size.[15]

In contests between P. clarus females, the preliminaries are longer but ritualized displays are rare. Physical fights between females are more likely to end in injury or death.[16]

Courtship of Phidippus clarus

Males of P. clarus can detect females' size and age based on pheromones and other chemicals left in females' silk, and males use this information to choose mates. Males prefer to cohabit with large females, which mature more quickly and have more offspring than smaller ones. The largest males are the most aggressive and thus the largest males and females mate, and so on in order of size.[6]

When P. clarus males find females, the males court by waving their legs and making their abdomens vibrate against the substrate (leaves, the ground, etc.). Males will court immature and adult virgin females, and also previously mated females.[6] As the male dances, he approaches the female and touches the female cautiously once or twice. The female rejects the male by extending her first pair of legs whenever he approaches too closely, or shows acceptance by not blocking his advance. If accepted, the male climbs over her and uses his forelegs to turn her abdomen to the side. The turn exposes her genital pore, which lies on the underside of the abdomen, and the male inserts one semen-laden pedipalp. After two or three minutes the male withdraws this pedipalp, turns the female's abdomen the other way and inserts the other pedipalp.[11]^{: 138–140}Some P. clarus females mate with more than one male. In these females, copulations after the first occur after longer courtships. This shows that already-mated females are less receptive to mates, and suggests that females may be trading up in subsequent matings.[14]

Male and female Phidippus clarus mating

The Californian wasp Aporinellus completus parasitizes P. clarus by paralyzing the spider and attaching an egg to the spider's abdomen.[17]^: 88–89 Mermithid nematodes infest P. clarus and many other spiders, typically severely damaging the main muscles, the digestive system and the reproductive system.[18]