By PATRICIA SIMPSON
Considering the number of amazing observations at Mission Trails Regional Park on iNaturalist (over 760 this June), it is only appropriate to look at more than one at a time. This month, we have a “twofer” by one observer.
Mark K. James is a trail guide at MTRP and, equipped with his iPhone and a macro clip-on lens, he has been photographing very small park inhabitants: a plethora of insects and arachnids. This month, Mark found two jumping spiders in the family Salticidae. The first one is Metaphidippus siticulosus (say that 10 times fast) seen here at www.inaturalist.org/observations/83298899. Congratulations to Mark on the first San Diego County iNaturalist record for this species!
The second observation is of an ant-mimic jumping spider of the genus Synageles seen here at www.inaturalist.org/observations/83039552. Individuals of this genus are nearly impossible to identify to species unless the specimen can be analyzed under a microscope. This is only the second record of this genus in San Diego County posted on iNaturalist.
Jumping spiders are fascinating creatures and are pretty darn cute! Maybe it is easier to relate to them because two of their eight eyes are considerably larger and located on the front of the face. This gives them a more “human” look. They are also small in size and come in a variety of colors and patterns (check out all of Mark’s jumping spider records for example: tinyurl.com/39w9z3hk). Some of them don’t even look much like spiders, as with the Synageles species. Ant mimicry (called myrmecomorphy) is a defense mechanism many insects use to avoid predation. Ants have a reputation for being territorial and most predators will avoid them.
Jumping spiders are amazing athletes able to propel themselves up to 50 times their own length. To achieve this without many muscles at all, the jumpers use controlled blood flow. A sudden rush of blood to the legs will cause them to extend in a burst. The ability to jump is what helps them be proficient hunters. Jumping spiders do not build webs to catch their prey, they actively stalk them and ambush them using a variety of intricate tactics.
Even though jumpers don’t build webs, they can and do produce silk. In fact, before they jump, they usually anchor a string at the original spot and if they miss their target, they can simply use the lifeline to come back to safety. They also build silk shelters for themselves where they can hide away from predators and rest.
Want to see a jumping spider in action? I highly recommend the BBC Earth video “Spider with Three Super Powers” (youtube.com/watch?v=UDtlvZGmHYk) which follows an incredible hunter named Portia in her quest for her next meal. To see the fun mating dance some males perform to woo a girl, check out this video filmed in a lab at the University of Pittsburg: youtube.com/watch?v=uGZwZlcCnDE. And if you are brave enough, next time you encounter a jumping spider in your house or yard, try holding a small mirror in front of them. They will often interact with the reflection (true and tried by me).
— Patricia Simpson is a trail guide at Mission Trails Regional Park.