Table grape spider keys

TGSId includes two separate keys, one to spider adults, and one to spider egg sacs. Both keys are best used with a dissecting microscope, but a hand lens may be sufficient for the egg sac key and for some species in the adult key.

Central Valley Spider Key

The key for spider adults includes 30 species of spiders from 24 genera and 15 families that are known, thought to, or may potentially be found in California Central Valley table grape bunches. Because most of the users of this key will likely not be trained arachnologists, the key is based on more highly conspicuous features than arachnologists would traditionally use. For this reason, features such as coloration are heavily relied upon in the key. This leads to the difficult situation that some spider coloration changes drastically in alcohol. For example, the spider Zelotes nilicola is jet black in life, but once place in alcohol, the coloration can change to gray or almost white. For this reason, it is best to examine specimens before they are placed in alcohol if at all possible. If this is not possible, keep in mind that coloration can change when you're using the key.

The features in this key were designed to lead to an identification as quickly as possible, and have been arranged so that the first ones listed should be fairly conspicuous and possibly unique. As you go down in the list of features, they become less definitive as identifiers. Some species have virtually no unique features, so you may have to examine more features further down the list before reaching an identification. Also keep in mind that the thumbnails that are provided to describe particular feature states are intended to serve as examples, and so they may not capture the entire range of diversity that the state is meant to include.

go to adult key


Central Valley Spider Egg Sac Key

The key for egg sacs found in California table grapes includes 11 species of spiders. The characters may not be completely diagnostic and may only allow you to narrow the identity to a group of suspected species, but they may allow you to eliminate all species of regulated status. Characters include overall appearance, whether the egg sac was attached to a substrate or was suspended in silk, and relative size of the egg sac (comparison image to a ruler for size reference). Additional features require carefully ripping the egg sac to expose the eggs and determine how many are present.

There are images of dorsal and ventral views of the emerged spiderlings in the fact sheets. NOTE: spiders undergo hatching AND their first molt inside the egg sac. After hatching, they are typically pale in color and lie on their backs fairly helpless until they molt to the second stage instar. Once molted, they still may not have their final coloration. The pictures in the fact sheets show spiderlings, both alive and in alcohol, AFTER they have voluntarily emerged from their egg sac. If you open a sac and the spiderlings are pale, it cannot be determined with certainty whether they are still developing or if they will remain pale once they emerge as viable spiderlings. Therefore, if you open an egg sac and the brood is beyond the egg stage, you may have to wait up to 2 weeks for the spiderlings to develop into full second instars before attempting an identification. This process may be sped up with DNA analysis.

In the egg sac key, we included only those species that are known to or might lay egg sacs in grape clusters. For some species, we were able to collect egg sacs but the sac was never in the grapes (encased in a folded leaf, hidden under loose bark). These spiders were excluded from the key, but images of their egg sacs were included in the fact sheets as a point of reference. Additional spiders were excluded because they carry their egg sacs around with them (wolf spiders (Lycosidae) on their spinnerets, cellar spiders (Pholcidae) in their fangs). These egg sacs should never be found in grape clusters. Keep in mind that spider egg sacs can look very similar to an insect egg sac or a pupal case for a moth.

go to egg sac key