You can tell the sex of spiders by whether they 'wear boxing gloves' or not. If you look at their heads, it seems as though they have two feelers attached. These are the pedipalps and they use them to hold prey. The male spiders use theirs to transfer sperm to the female. They put sperm onto the web, then dab their pedipalps into it. Female pedipalps are long and slender, whereas male ones are quite rounded at the ends - the 'boxing gloves'. This difference is quite distinct and easy to see even on very small spiders - if you can see the spider, you can probably see its pedipalps.
And the reason I mention this? There really are a lot of these big, orb-weaver spiders around at the moment, and I often look to see whether they are male or female. Most of the ones I am seeing are female. One possible explanation for this is that food will be less plentiful in the winter and they still need to use their body's resources to lay eggs and spin a substantial cocoon to protect them. Some species of orb-weavers die as winter approaches, but the eggs must survive and hatch in the spring.
Posted by Janis