Monday, 9 June 2014

Spider eggs and egg sacs

Spiders make remarkable mothers. One of the most widespread maternal behaviours is the more or less elaborate construction of an egg sac, and many species are making them at this time of the year. The mother wraps a batch of eggs - which might be the only one she will produce during her lifetime - into a neat parcel kept together with silk. The egg sac can protect the eggs from parasitic wasps, or from predation - sometimes from other spiders. In addition, egg sacs are often guarded by the mother, like the Neriene montana above (28/05/2014) or Garden spiders (below), Araneus diadematus, which guard their large egg sacs until they die at the end of autumn (30/10/2011).
Holding the egg sac is another maternal behaviour. An example is Pholcus phalangioides, the splindly daddy long-leg spider. She makes a simple egg sac, with the eggs clearly visible through the lax packaging. She keeps the eggs on her mouthparts until the spiderlings hatch (22/07/2009).
Being mobile spiders, wolf spiders and nursery web spiders actually carry their egg sac with them wherever they go. This allows the eggs to develop faster, as they warm up when spiders bask in the sun.
Wolf spider, Pardosa sp. carrying her egg sac (31/05/2011), attached to her abdomen.
Nursery web spider carrying its large egg sac (19/06/2011).

In the family Gnaphosidae, the female not only guards the eggs, but she makes her egg sac inside a folded up leaf, locking herself inside with the eggs (19/07/2010):
But egg sacs are often found alone. Some of them have a stalk, like those of the genus Ero, also distinctive by their covering of coarse red silk (7/04/2013):
Others are truly unique, and is the best way to identify the species, like the sputnik-like egg sac of Paidiscura pallens, a tiny spider (28/05/2014).
Eggs vary in colour, I love the soft pink eggs of Steatoda bipunctata (28/05/2014)...
 ...and also the baby blue silk of Enoplognatha sp., revealed here while picking apples (30/08/2011):
These are just a few examples, from common spiders you can find in your own garden, which illustrate some of the diversity of spiders.


Anonymous said...

you misspelled Gnaphosidae ;)

Unknown said...

What can you do if you find a daddy long legs spider with an egg sack

Wilfred Duffin said...

What can you do if you find a daddy long legs spider with an egg sack