Leitz Ortholux microscope
4X Leitz projection eyepiece plus 1/3x relay lens
171 images at 2.5 micron increments. Nikon 10x Achromat
Diffused Fiber Optic illumination
Zerene PMax and Photoshop processing.
What we have here is the underbelly of a spiderling that is of the Cribellate type. As detailed in Spiders No. 40, the cribellate spiders have a silk producing organ other than the spinnerets called a cerebellum. It is flat or plate like in SEM images and is located I believe in the clear zone just above center on this young spider. The large number of hairs that normally obscure it are not yet developed.
This image is of a live subject resting in its web. Some of which can be seen in the image.