Lesley Smitheringale Fine Art

Garden Guests Diary - Bird Dropping Spider [23 March 2008]

I did my usual walk around the garden today and it never ceases to amaze me that it is different, no matter how many times I go out there.  I sometimes think, camera dangling around my neck, that it will be a useless endeavour, that as a photographer, “I’ve been there, done that” but I can assure you, every time I go out to my yard, nature has beaten me to it, with many new things on display.

For instance today, I went “wow” when I saw these manifestations in my garden. 

Bird Dropping Spider and its Egg Sacs

The Bird-Dropping Spider sits motionlessly on a leaf during the day but is active at night. This spider has evolved an effective strategy against being eaten by day-time predators such as birds and wasps due to its camouflage which looks like unappetising bird droppings. They are dirty white, grey and black in colour with a very large abdomen.

Bird-dropping Spiders are also know as Death’s Head Spider because if you look at them from the top they look like a skull.

Scientists found out that the spiders give off a scent which attracts a particular species of male moths. The spiders release pheromones that mimic the sex scent of Lawn Armyworm female moth (known as “aggressive mimicry”) attracting unwary male moths and attack when the moth come close. The spiders grab the moths with their strong front legs.

From late summer to early winter, female Bird-dropping Spider makes ball shaped egg sacs. The egg sacs are brown in colour with dark line patterns, about 10 mm in diameter, sometimes tied loosely together by webbing. The egg sacs are quite commonly found hanging on plants but not recognized for what they are. Up to 10 sacs are silked together in a group, beneath which the spider may be found sitting by day or hanging by night, awaiting prey. The female Bird Dropping Spider spends large amount of time on making her egg-sacs. The spider usually hangs her egg sacs under leaves about one meter from ground. She usually start to build egg sacs after evening. After she finishes two or three preys, her abdomen becomes very large, she starts to make another egg-sac. She lays hundreds of eggs on a silken sheet, then bundles it up into a small ball, about 10mm. She further covers the ball with layers of silk and finally extracts some liquid on the silken ball which makes it turn into a dark brown colour. Then she hangs the egg-sac together with other egg-sacs she has already made. The mother spider usually guards her egg sacs until the young spiders emerge. The baby spiders emerge in late winter or early spring and disperse by ballooning.

Info found at  http://www.geocities.com/brisbane_weavers/BirdDroppingSpider.htm