Long-jawed spiders

Tetragnatha extensa,

female

Among the orb-web building, the long-jawed spiders are very widespread are easily found in bushes and in the meadow, especially if close to a source of water. Scientifically known as Tetragnathidae, the name “Long-jawed Orb Weavers” are due to their large chelicerae (fangs), which are, in some species, longer than the spider's cephalothorax (anterior part of the body). As in the case of true the orb-weavers (Araneidae, like the garden spiders), long-jawed orb-weavers spiders build circular webs. However, the spider web usually do not have as many radii, or "spokes," as those of true orb weavers, and their circular web is usually parallel to the ground. Both males and females build webs, but when the males reach the sexual maturity they tend to move, hunting as stalkers and squatting other spider webs, especially the ones built by the long-jawed females. Their typical dishes includes any kind of arthropods of “right” dimensions that came across their webs. I have frequently found tetragnatha eating flies, adult antlions and lacewings.

Long-jawed spiders live close to the water, and frequently they build their web over ponds or streams. Actually they do not fear water contacts, since they can also 'walk on it'! Exploiting the surface tension in case of need they can walk as water striders (Gerridae) but with two pairs of leg together (the two anteriors and the two posteriors for each side of the body tight together). Long-jawed are very good water walkers, actually they are faster on the water than on the ground, achieving a speed of 10-15 cm per second.

Long-jawed spiders are slim creatures with long legs. This shape helps them to camouflage themselves in the meadow as small twigs. Moreover they can also stretch and flatten their body against flower stems to hide from predators. Their dimensions ranges from half to more than one centimeter, depending on the species. The largest European species is Thetragnatha extensa which exceeds a centimeter.

Tetragnatha female eating

As happen for all other spiders, their life cycle consists of simple metamorphosis. The young long-jawed spiders hatch from eggs and look like tiny adults, then they shed their skin as they grow. Their life is not long and the majority of spiders in this family live for less than one year. Typically, the adults mate and lay eggs in the late summer, and the newborn spiders hatch during the following spring. No special care is performed by the females to protect their eggs, which are laid in several sacs in different times during the female life. Actually the female has a special cavity in her abdomen that can keep the male sperm (spermatheca), so that she can use the male's semen several times. Well, it would be more correct saying the males' sperm, since they mate several times with different partners. In this respect it in interesting to know that long-jawed belong to the family of those spiders that have a “cul-de-sac” spermatheca. The sperm enter and leave by the same duct, a FIFO (First-In-Last-Out) system in informatics jargon . This means that, at least in theory, the last male mating is the one with more chances to have related progeny, which is technically called “last-male-priority”.

You can imagine that differently form the spiders that have a “first-male-priority” (in this case the females' spermathecae are "conduits" ), it is not easy for the male to play a game that assures highest chances to be the last-mating. In fact, it seems that males tend to aggregate closer to the females during their egg-laying period than before. This may indicate that when a long-jawed fellow sense that there is a female ready to laying eggs, he tries the “last-male-takes-all” mating strategy.

Tetragnatha mating

Mating always occurred on or at the female's web and it is not restricted to any particular time of the year. On the contrary, mating take place at varying frequencies during the entire adult period and it happens very frequently. Actually, when a male came across a possible bride, he try to, and quite often successfully, mate with her. The courtship is very short and when the female is receptive she open the large jaws “inviting”. The male then runs towards the open fangs and lock them with his own, which are even longer than the female's one. Thus the mating activity start as usual in the spiders, by using the male palps imbibed with his sperm to enter in the female organs. The mating is vary short for spiders and lasts no more than 10-20 minutes.

After their sex activities the males stayed with the females for a variable length of time, from just a few minutes up to a maximum of ten hours for the most relaxed. Thus, there was no obvious guarding of the females to prevent her mating with somebody else! It also seems that direct fight between males is a rare event, even in case of disturbing activity, such as biting the couple by an intruder to stop the couple. This again may be due to the fact that the last win all (or more), so that it may be more convenient wait for a while and retry.