The Fen Raft Spider displays a remarkable degree of maternal protective behaviour. the fact that many higher animals (for example reptiles) show no protective behaviour for their young as soon as egg laying is over makes this all the more remarkable.
The following pictures were taken whilst on a routine survey of the Carlton dykes in mid July 2019.
The next three show two females carrying egg sacs. The first two pics are of the same lady, the third is a different individual.
She has wrapped her eggs in a silk cocoon which has turned a brown colour due to oxidation. She will carry them like this until they are ready to hatch. Then she will build a nursery web for them and help them out of the sac by picking a hole in the silk.
Here’s a ball of hatched spiderlings in a (fairly thin) nursery web
Mum guarding the nursery. You can see two balls of spiderlings in the web above her.
Another mum with her nursery. She has a thin abdomen and could be mistaken for a male, but the non-clubbed palps give away her gender. She has eaten very little for weeks, being too busy carrying the sac, and guarding the nursery to hunt. This is on top of the massive energy expenditure in creating her young, the egg sac, and the web. Slimming World could learn a thing or two from her. It has just rained. Spider surveyors are a dedicated bunch!
Here are a few spiderlings on the move within the web.
This is a male. I’ve included the pic only because it displays so beautifully how the fen raft spider is perfectly adapted to aquatic life -walking on water. His first left and right legs are resting on the water, feeling for vibrations in the meniscus, possibly signalling the arrival of the next meal.
Another male -see his clubbed palps in front of him -the “boxing gloves”. These are full of sperm transferred from his primary genitalia and stored ready for mating. The shot is slightly fuzzy as I’ve enlarged it considerably to show his eyes and the palps. He has uncommonly bright bands and you can see his two rows of eyes at the front of the cephalothorax (combined head and chest).
Males don’t have anything to do with the nurseries or young -they are basically sperm donors in their world. I have included this shot not because it’s particularly good, but because it took me ages to get the view and exposure I wanted, He was in a relatively dark recess at a distance. I sweated over it!