School Malaise findings 3 - arachnids

Today two bits on our little friends with eight legs. We found quite a few in all the Malaise traps. Some expected, some unexpected.

Erigone atra

Dwarf spiders (Erigoninae)

Dwarf spiders are members of the sheet weaver spiders the second largest spider family in the world. There are more than 2000 described species of these spiders found around the world, with 650 in North America. They are very small, usually less than 1 mm, and vary in colour. Their small size allows these spiders to use “ballooning” as a method of transportation (see video below). When ballooning, the spider shoots out strands of silk that form a sort of parachute which is caught by the wind, floating them to a new location. As with most spiders, the Erigoninae are predators and play an important role in food webs. 

We were able to find two species of this subfamily new to the BOLD DNA barcode library. One specimen of Ceratinops crenatus and two specimens of Walckenaeria tibialis were at two schools.

There is only little available information about the biology of these two species as they are very rare.

Pseudoscorpions (Pseudoscorpiones)

Pseudoscorpions arachnids named “Pseudo” scorpions because they have pincers that resemble scorpions, but do not have the tail and stinger. They can be found anywhere from a tree canopy, to somewhere in your home where they feed on the larva of some household pests.

They can also be found in leaf litter, where they feed on other tiny arthropods. Males use  pheromones, and dancing behaviour, to attract females to mate.

These arachnids construct a silken cocoon which they use to protect themselves during the winter. Pseudoscorpions occur globally, but are rarely collected in Malaise traps. In total, four specimens were caught in the School Malaise Trap Program (out of 95000 specimens!).

Here an interesting video of a pseudoscorpion hunting springtails: