#spitting spiders

[inatarachnids]

Brown Spitting Spider (Scytodes fusca)

Observed by boingohamster, CC BY-NC

[look-at-a-speck-on-the-ground]

I'm getting braver with spiders! once again with a little spitting spider lol

[arachnophanatic]

Here’s a spitting spider / Scytodes sp. I saw in the bathroom at work (who really confused me at first, because she’s clearly not a brown recluse but I forgot that recluses aren’t the only spiders who only have six eyes)

[bugsicles]

Spooky Season Special: The Spitting Spider

In honor of the month of October, a post about one of the creepiest crawlies I've crossed paths with thus far

First off is a spider with a giant pumpkin head and jack-o-lantern face: the spitting spider (Family: Scytodidae).

This unique spider goes about catching prey in an unusual way - instead of constructing a web spun with silk from the spinnerets on its abdomen and waiting for a catch, it roams for its favorite food - other spiders - and once within firing range it shoots a gluey, silky net from its mouth to pin the prospective meal to the ground. It then proceeds to envenomate the restrained victim and wrap it with spinneret silk in more typical spider fashion. Their web-like spit projections, enlarged heads, and unusual eye arrangement distinguish these prowling night-time hunters. And given that they enjoy indoor living and are common in the U.S., there's a pretty good chance that one is haunting your household as we speak.

Figure 18.1, Suter & Stratton (2013)

In a way these spiders have re-invented silk, for while they produce conventional spider's silk in their abdomen, they also figured out how to make a functionally similar substance in their mouths. The friend in the photographs above has such a rotund 'head' precisely because of its saliva-generating needs. The cephalothorax houses the enlarged spit glands, which feed through the chelicerae (the two mustache-like appendages in front of the mouth), at the end of which sit the fangs (see below). Some of these glands produce venom, and some produce the fibrous net material and sticky substance that is squirted from the fangs when attacking prey (or attempting to dissuade a predator with a web pie to the face). Whether the net is laced with venom seems to be up for debate in the literature. Streams from the 2 fangs make an alternating zig-zag pattern, and this woven mesh contracts after it is fired, often pinning the quarry's legs to its body, in addition to binding the creature to the floor.

Chelicerae (a) and fangs (b) of a spitting spider (Figure 18.4, Suter and Stratton 2013).

It takes the spitting spider ~20 milliseconds to generate ~2 feet of silky string, oscillating its fangs at ~1000 wiggles per second to weave its net in midair. And it looks as cool as you would hope it would - videos from the first author of a great book chapter I found, from which much of this information is sourced, can be found here. The chapter, "Predation by Spitting Spiders: Elaborate Venom Gland, Intricate Delivery System" by Robert Suter & Gail Stratton, is very accessible and contains lots more awesome information about these spiders (read here).

Videos by Robert Suter

According to the authors, muscle-driven oscillations greater than ~500 cycles per second are rare in nature, given the time it takes for muscles to relax between contractions. So it seems unlikely that the spider is able to wiggle its chelicerae so fast on its own. Higher frequencies are possible when things other than muscles are driving the cycles, and in this case the authors suspect that the fang-silk system is behaving the way a water hose does when turned up all the way with its end free to lash around. The silk-glue is forced out of the fangs so fast that they jiggle in response, with a frequency determined by their mass and the elasticity of the connective tissue of the chelicerae. The relatively small fangs of this spider may be that way since they allow quicker oscillations for a more tightly woven mesh trap (though the authors note some conflicting evidence, including the fact that the larger fangs of some species in the group do not appear to wiggle more slowly than others). Regardless, this is all I'm going to think about when I use a hose now.

I had never heard of spitting spiders before coming across this individual in my home the other night, and I suspect the same is true for most people, which is surprising given how common and rad they are. There doesn't seem to be any end to the fascinating goings-on right under foot!

Sources:

Suter, Robert & Stratton, Gail. (2013). Predation by Spitting Spiders: Elaborate Venom Gland, Intricate Delivery System. 10.1007/978-3-642-33989-9_18. https://www.researchgate.net/publication/268069024_Predation_by_Spitting_Spiders_Elaborate_Venom_Gland_Intricate_Delivery_System

Spider. Encyclopaedia Britannica. https://www.britannica.com/animal/spider-arachnid

bugsicles is a blog about the bugs I find in my backyard in southern New Mexico. I don't use any special equipment beyond a cheap jeweler's loupe and a phone camera, and occasionally an amateur microscope.

[humblegrub]

University of Florida Department of Entomology and Nematology Coloring Book

University of Florida Department of Entomology and Nematology Coloring Book About the University of Florida Department of Entomology and Nematology: The Taylor Lab’s research focuses on communicati…

did you know that the University of Florida released a coloring book as part of the Color Our Collections project by The New York Academy of Medicine Library?? you can download it as a pdf at the link above!!  

[inatarachnids]

Common Spitting Spider (Scytodes thoracica)

Observed by urenzal, CC BY-NC

[look-at-a-speck-on-the-ground]

another spitting spider! I wanted to get a photo of this gentleman but he wouldn't stop running around on the bathroom floor, so I decided to be brave! He gently touched my hand but did not climb on - but at least he stood still for some photos!

[look-at-a-speck-on-the-ground]

I finally learned that this is a spitting spider! I thought they were cupboard spiders but their legs are far too skinny. nice to finally have an ID for both species!