Ghosts in the night

This summer I’ve spent quite a few nights hanging out along the Mississippi River—lamp on my head, vials in my pocket, and an ultraviolet (UV) light setup on the sandy banks. UV light collecting for insects (also called “blacklighting”) is a popular method among us beetlers, but for a number of reasons it’s been a while since I’ve done a lot of heavy blacklighting myself. That all changed this year when I decided I needed to get a better handle on the Missouri distribution of two species of tiger beetles, Ellipsoptera cuprascens and E. macra, found only in sandy habitats along the shores of the state’s two big rivers—the Missouri and Mississippi—and, fortuitously, attracted to blacklights at night. Blacklighting alongside these big rivers is a relatively new experience for me, as my previous experiences have been mostly in forests—either here in the Midwest or out in the desert southwest. Along the big rivers, as soon as the sun dips below the horizon hordes of hungry mosquitos descend upon me and choking swarms of caddisflies quickly envelop the blacklight. Liberal application of Deet keeps the mosquitoes at bay, but checking the sheet behind the blacklight to see if anything of interest has landed requires a bit of a mad dash and a quick retreat, all the while holding my breath and clamping the shirt cuff around my neck to prevent the swarming bugs from flying into spaces where I don’t want them.

Arctosa littoralis (beach wolf spider) | Lewis Co., Missouri

Wandering away from the blacklight and exploring along the beach in the black of night is also a relatively new experience. While I’ve done a fair bit of night collecting away from the light, again this has tended to be in forests and woodlands with a beating sheet in hand looking for jewel beetles, which still hang out on the same host plants they can be found on during the day but are far less inclined to zip away as soon as they hit the sheet like they do when the sun is high overhead. I haven’t spent much time shining a lamp on the sand of a big river beach, so I wasn’t quite sure what to expect (other than hopefully a tiger beetle!). As I walked along the beach, I occasionally saw blue-green glowing dots on the sand—I recognized these fairly quickly as the eyes of spiders reflecting the light from my headlamp. However, at first when looked closer at the spot where I thought a spider should be sitting I didn’t see anything. It took a few tries before finally I saw ghost-like movement on the sand, and when I moved cautiously and got down close to the sand I finally saw a magnificent, white wolf spider sitting motionless—perfectly colored to blend into the sand on which it was sitting.

The mottled, white coloration is conspicuous on wet sand…

I quickly hurried back to the car and got my camera, set it up with a 100mm macro lens and extension tubes (hoping I could get real close), and went back to the spot where I’d seen the spider to see if I could find it again. I didn’t, but not too much searching was required before I found another one. Unfortunately, I didn’t succeed in photographing that one either. It was apparent to me that I was going to have to use the same ultra-cautious and slow movements that I use with tiger beetles if I was going to succeed in photographing one or more of these spiders. I quickly figured out that they were easier to see if I looked right along the water’s edge, as in that situation the white coloration of the spider actually stood out against the darkened, wet sand. (Of course, photographing them on the wet sand was a tad dirtier for me, but I’m not afraid to get filthy dirty when it comes to photographing arthropods.) I also figured out that I could more easily find the spiders on the wet sand and then follow them up to the drier sand for photos that better showed just how marvelously cryptic their coloration was.

…but provides perfect camouflage on the dry sand further away from the water’s edge.

Those of you familiar with my work know that I love frontal portraits, but I found this to be almost impossible during my first attempts. It was hard enough approaching the spider from the front without it bolting before I could get set behind the camera, but in the few cases where I did actually manage this then it would bolt as soon as I made any microadjustment in the position of the camera to compose the shot. It occurred to me that the spider was sensing vibration from moving the camera on the ground (ground-resting the camera is a technique that I use commonly to get the lowest possible angle on my subjects)—makes sense, as spiders are intensely tuned into vibrations for  prey capture. Once I began keeping my hand flat under the camera as sort of a makeshift “beanbag” I was able to make the final adjustments necessary to get shots like the one shown below and in ID Challenge #20.

Active primarily at night, the spider’s eyes glow blue-green when hit by light.

According to Dondale & Redner (1983) this should be Arctosa littoralis—widespread in littoral habitats across North America but, at least at the time of their revision, not recorded from Missouri [in fact, it seems no species of Arctosa was known from Missouri until A. virgo was recorded from oak-hickory forests in the southern part of the state by Bultman (1992)]. I’ll leave it to the spiderphiles to determine if this actually represents a new state record or (more likely) if I just haven’t dug deep enough into the literature.

Congratulations to 3-time champ Ben Coulter, who swooped in from his hiding place with 30 pts to win ID Challenge #20—the final challenge of BitB Challenge Session #6. It wasn’t enough, however, to disturb the overall standings, and Brady Richards maintained his overall lead with 28 pts to win Session #6. Sam Heads was just one point away from the win in this challenge, but his 29 pts were enough to earn a tie for 2nd place in the overall standings with Mr. Phidippus, who finished a respectable 4th place in this challenge. Nobody else came close to these three gentlemen in the overalls, so they deserve their accolades and loot (please contact me for details on the available choices). In case you haven’t been following along, here is a summary of the BitB Challenge champions to this point, listed by session:

1. Ben Coulter
2. Ben Coulter
3. Max Barclay
4. Ben Coulter
5. Mr. Phidippus
6. Brady Richards

REFERENCES:

Bultman, T. L. 1992. Abundance and association of cursorial spiders from calcareous fens in southern Missouri. Journal of Arachnology 20:165–172.

Dondale, C. D. & J. H. Redner. 1983. Revision of the wolf spiders of the genus Arctosa C . L. Koch in North and Central America (Araneae: Lycosidae). Journal of Arachnology 11:1–30.

Copyright © Ted C. MacRae 2012