Wednesday, January 31, 2018

Argiope Trifasciata Spider--Doggone Buggone at 2018 Start

Tch! On the last day of 2017, I took pix and video of an argiope trifasciata spider. (For background, read "Argiope Trifasciata Spider--Final Bug Spotting of 2017".) The next morning, I went to the web; she was nowhere to be found. Over the next few days, we’d peered into the plant—no sign of the spider, nor indicators of web disturbances, nor egg sac.

I’m guessing that the spider did not undergo a "normal" life cycle. From BugwoodWiki's “Banded Garden Spider”:
The overwintering stage is the eggs, which are protected within an egg sac attached to vegetation. Upon hatch in spring the spiderlings disperse, … Adult males begin to appear in late July and females shortly afterwards. The males wander while the females remain within a web. Mating occurs in the latter half of the summer and females produce egg sacs, … Freezing temperatures kill off all remaining spiders at the end of the season and they have a one year life cycle.
I’m going out on a limb here. The case for the spider to not having been there in the summer and fall is lack of any egg sac since having spotted her on New Year’s Eve. I propose that the weather, fast approaching freezing, resulted in lack of prey or male, possibly (probably?) influencing her to abandon her web.

I gleaned the following temperature info from December 30 through January 3 results, using Weatherunderground's Wundermap for my area:

December 30 temps—high in low 60s at noon, temp 49ish around 8 PM when we spotted the spider.
December 31 temps—40 at AM start, 37ish around 8 AM when I took pix of the spider, gradual temp drops.
January 1 temps—mid-20s at AM start, less than 30 throughout the entire day and evening.
January 2 temps—lower than 30 throughout the entire day and evening.
January 3 temps—20s at AM start, climbing to 30s around 9 AM, climbing near 60s around 4 PM, then cooling down as evening progresses.

I speculate that the spider constructed the web during reasonable temperature, before the freezing temperature set in and that lasted a few days. During the freeze, prey maybe didn't approach the web (unwittingly or not); thus, no food for the spider. No male argiope trifasciata spider approached the web for mating; thus, no need for the female to create an egg sac.

A few successive days of looking at the plant and noting the intact web, I sensed the female abandoned the web. I ruled out the possibility of a predator making a meal of the spider. I think a struggle would have resulted in the web being wrecked.

One other oddity: The orb web did not have a stabilimentum (elaborate web decoration) as I've noticed in several other images of female argiope trifasciata spider webs. The lack of stabilimentum might have indicated the stoppage or interruption of the spider's "housekeeping setup" process. Read more about stabilimenta.

Curious about doing your own weather timeframe lookup? Start at https://www.wunderground.com/wundermap.
  1. Confirm or click All Layers > Weather Stations > Temperature / Wind.
  2. At the search field, enter your city of interest, then enlarge the view to the scale you want.
  3. Scroll to the area of interest. (The results might be slow to arrive.)
  4. Click a number. When the inset window opens, click Visit local weather page for [your locale].
  5. At the new window, scroll down to the weather history options. The first option is interval, the default being daily. You can set for larger intervals or customize for date range. View graph or table.
  6. The newer window has an enlargeable inset map with additional station numbers you can click and find similar information.

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