Migrant hawkers scramble competition

I'm used to watching migrant hawkers foraging over gardens, leafy streets and sheltered woodland rides, some times in groups. They are immature individuals, gathering energy away from water. Migrant Hawkers, unlike other hawkers, mature slowly, and will move to suitable breeding sites after their long immature period. During this past week I've watched them in their breeding sites in lakes and drains, where mating and egg-laying takes place.

A mature male rests briefly between bouts of searching (Pickering Park, 27th August) 

Males at the breeding site 
At one of my local parks (Pickering Park) last week, dozens of Migrant Hawkers sat or patrolled alongside marginal vegetation around the lake. The males, now fully mature and showing their bright blue spots and eyes and side yellow-green stripes often hovered in a spot, or explored the vegetation, flying well into it, searching for females.

A typical hovering male in a clearing at the marginal vegetation (Pickering Park, 27th August), offering them good views.

Mating
I saw no females, until one was captured by a male: no preliminary or courtship, the male just tackled her and positioned himself to grab her by the head. The female is then able to curve her abdomen and mate, retrieving sperm from the male's secondary genitalia at the base of the abdomen, forming the 'wheel position'. They may fly in wheel position very fast, zigzagging alongside the marginal vegetation edge or briefly rising into the air, before settling on vegetation (above).

Ovipositing female (Foredyke Stream, 1st September)

The moment when the male passes by, and sees the female.

The pair, mating.

Oviposition
A couple of days ago I watched a patrolling male on a ditch doing its usual patrolling routine, rising to inspect any passing individual, even paying attention - briefly rising - to birds flying over. A mated female arrived, unnoticed, and started laying eggs on live leaves well above the water line, I'd say over one metre over the water. She checked leaves and unsheathing her ovipositor, started laying into them (the eggs will overwinter inside the plant leaves, where they are protected from predation). After a couple of minutes, the male noticed her, tackled her and mating ensued. This time the pair settled briefly on plants, which allowed me to take a shot (above). Mating in Migrant Hawkers is longer than in other territorial relatives.

Two males resting near each other (Pickering Park, 27th August)

Nonterritorial males
This species is notoriously non-aggressive, even at the breeding sites. Males will even rest within view from each other (above). A patrolling male will swiftly rise to check a passing one, but the interaction is suggestive of them 'checking' that they are not a female, and letting the other individual go their way if it's a male. There is no defended territory, just males congregating on suitable ovipositing sites and searching for females, a type of mating tactic called 'scramble competition'. This appears to be the reason behind the long copulation. A territorial male mating for a long time may lose the territory to an invader, or miss extra mating opportunities. A nonterritorial male has less to lose, and therefore makes sure that he fertilises as many as possible of the females' eggs, possibly by taking time to remove any previous sperm before transferring his transfer. These patterns have been shown to stand when the copulation duration of territorial and nonterritorial drogonfly species were compared, but I haven't found specific data on the Migrant Hawker. To illustrate the pattern, the Emperor, a territorial species, copulates for an average of 10 min, while the Common Hawker, a non-territorial one, copulates for an average of 67 min. Of course, this lengthy copulation is not necessarily to the benefit of the female, who may be already mated, as the female already laying eggs, and therefore this sets the stage for the evolution of female counter-tactics, such as visiting the water as little as possible and avoiding males if they can, something I have covered before at Bugblog.

More information
Córdoba-Aguilar, A., Serrano-Meneses, M. A. and Cordero-Rivera, A. Copulation Duration in Nonterritorial Odonate Species Lasts Longer than in Territorial Species. Ann. Entomol. Soc. Am. 102, 694–701 (2009).

Male garden spider

We found this male garden spider, Araneus diadematus, on our garden gate, actively walking about. Male garden spiders are on the lookout for females in August and September, when they become adult and receptive. This was a large and handsomely marked male, so I gave it a session on the white bowl and then released him near the largest female in the garden.

Black Lace-Weaver wanderer

 In springtime male Black Lace weaver spiders roam in search of females. This one was dangerously walking on the pavement this morning, cold and wet from the night's rain. I took some quick shots and took him home for a white background session. The male palps look like they are holding white balls, these are the characteristically white and very visible palpar organs in this species.
 Black-lace weaver females (Amaurobius ferox), as their smaller relatives Amaurobius similis, have remarkable maternal behaviours, including guarding the spiderlings, feeding them using unfertilised eggs and then finally, encouraging them to eat their own bodies (matriphagy). For a fantastic video documenting this spider's maternal behaviour see this Arkive entry.
 More info in the British Arachnological Society page.

Male garden spiders out on a mission

Even my four year old has noticed that there are lots of spiders about. She found many fresh webs by Araneus diadematus today, and she asked why are there so many now. I tried to explain that they have grown large recently, and that's why we are seeing them more easily, but she discarded this and came up with her own explanation: is her watering the plants yesterday what must have made them grow. Female Araneus diadematus are reaching quite large sizes now, although there is a lot of size variation. The record holder in our garden sits by two rubbish bins, and has probably been gorging on the flies the rubbish attracts. Males have also reached adulthood and, in contrast to the sit-and-wait females, are moving between bushes in search of receptive females. I have come across three in the last few days. They have slimmer abdomens and robust legs and their palps are quite noticeable. The male must be careful, though, as females will quickly make a meal of him if he does not reach their high standards. I found this male getting closer to a small female's web. As he was on a broom, focusing him was very tricky and I resorted to trying the white bowl.

Fearsome stripy jumper

Given the current rainy weather, I was pleasantly surprised to find this male Zebra Spider, Salticus scenicus, on my conservatory wall, inside. Zebra spiders have a bare black body, with white scales and some brown scales on the abdomen. They are warmth-lovers, coming out of their hiding places on clear days, often on walls after they have been heated by the sun. Salticus males have huge chelicerae for their size (a tiny 5 mm!), and they can be seen moving their palps over their black chelicerae as they move about. The chelicerae are opened in a display to rival males, and, if the contest escalates both males will face each other and lock their opened chelicerae together in a sparring match, as shown on this video in Arkive featuring a fight:

A top view of the male Salticus scenicus

Another male showing more brown (photo 20/04/11). The angle allows to see the long fangs folded underneath. Relative to its size, I think they are longer than in Dysdera.

 Despite their tiny size, Salticus make fearsome hunters. A few years back I surprised this male with a fly larger than him.

Male Salticus scenicus with fly (13/05/2009)

Female on 30/04/2011

Do you recognise this female? She is featured in the Bugblog banner. You can see her smaller chelicerae and white palps. Often females have beautifully marked black and white abdomens which give this spider its English name.