A Preliminary List of the Spiders Collected from a Giant Web at Lake Tawakoni, Texas

by John A. Jackman, Allen Dean, Mike Quinn

submitted on September 7, 2007 at 3:51 PM

A large spider web was reported at the park about August 24, 2007.  Images of the webbing were posted on the Texas Parks & Wildlife Department (TPWD) web site within a few days.  The story was picked up by various news outlets and distributed in print media and the internet within a few days.  This study and report was undertaken to investigate this occurrence.

Methods

Mike Quinn traveled to the Lake Tawakoni State Park (LTSP) on August 31.  He observed and sampled at the web site from 10:00 a.m. until approximately 8:00 p.m. between intermittent rains.  Specimens were collected individually by the use of a beat sheet to knock down the spiders and by manually capturing them with jars or forceps.  These spiders were preserved in alcohol or retained live. On September 1, he arrived in College Station with samples of specimens collected at the site.  

Spider identification was completed at the Texas A&M University Insect Collection (TAMUIC) by Allen Dean.  Spider identification at the species level typically requires specimens of adult spiders to compare genitalia to previously identified specimens. Consequently, all adult spiders were identified to the species level.  However, immature specimens and a few of the less common adult specimens were only identified to the family or genus level and were noted as undetermined or left as sp.  The TAMUIC is the repository for specimens from this study. 

Results

A summary of the spider taxa and numbers collected is provided in Table 1. Samples contained 250 specimens in 12 families.  The samples contained at least 16 identified genera. 

The spiders sampled included 151 Tetragnathidae, 46 Salticidae, and 19 Araneidae.  These three families represented 60.0 %, 18.4 %, and 7.6 % of the spiders in the samples respectively.  These three spider families accounted for 86 % of the spiders collected.   

Discussion

The collecting techniques did not sample all spiders equally.  Ground dwelling spiders, nocturnal species, and those that hide rapidly like Agelenidae, are likely to be dramatically under represented in the samples.  The general impression of the webbing over the foliage suggests that the web was created by funnel web spiders.  Their numbers are likely to be under represented in the sample because of their rapid movement and ability to hide quickly when disturbed.  The contribution that spiders in these groups made to development of the large web may be under represented based on the number in the samples.

Various hypotheses have been proposed about the spider involved.  The hypothesis that the webbing was made by a communal nesting spider such as Anelosimus studiosus has no evidence to support it based on the observations because this species was not collected in the sample.  The hypothesis that the webbing was caused directly by mass ballooning is questioned because webbing continues to be constructed at the site.

Based on the number of spiders collected, it seems clear that tetragnathid spiders contributed a large part of the webbing.  However, the diversity of the spiders in the area suggests that many spiders contributed to the development of the large web formation. 

Table 1.  Spiders Collected from Lake Tawakoni, Texas (Hunt Co.) on 8-31-2007 by Mike Quinn.  Identifications completed by Allen Dean. 

* Indicates penultimate stage or males with deformed palpi.