100-Million-Year-Old Spider Attack Found In Amber

EVERYONE, THIS IS HUGE!

As of two days ago (on October 8, 2012), the first ever fossil evidence of a spider attacking prey in its web was discovered! Yes, there have been fossil documentations of spiders around this time, the earliest fossil dating around 130 million years ago. However, no fossil evidence has surfaced to give us any indication of social behavior in ancient spiders until now! The juvenile spider's assault has been preserved with remarkable detail by tree resin that flowed over the event in the Early Cretaceous between 97-110 million years ago! This is the era of dinosaurs! Take a look:

Image source: http://oregonstate.edu/ua/ncs/archives/2012/oct/fossil-ancient-spider-attack-only-one-its-type-ever-discovered

The amber captures two ongoing engagements on the silk web: 1) between male spider and its ensnared parasitic wasp prey (above) and 2) between male spider and Neuropteran (image below). (Poinar and Buckley 2012). 

Image source: Poinar & Buckley 2012

The spider has been described as a member of the family Nephilidae and (new) genus Geratonephila, and within that genus has been named burmanica, so G. burmanica is its binomial nomenclature name.  

The wasp has been placed in family Platygastrida and (new) genus Cascoscelio. After a very involved diagnosis, the species was binomially named Cascoscelio incassus ("Casco" is from the Latin 'cascus' for old). 

The fact that a male and juvenile are present in the same web implies the presence of a female since extant nephilids live in female webs, as seen in the image below. Having a web occupied by both a juvenile male spider and a female maximizes the productivity of the web: the spiders living on the web can cooperate to get food and build the web. However, the spiders must be able to get along to share a living space. The presence of the juvenile spider indicates that intraspecific aggression and cannibalism were maintained at a minimal level, which are characteristics of social spiders. (Poinar and Buckley 2012).

Source: Poinar and Buckley 2012

Silk was also traceable in the amber fossil. At least 15 unbroken strands extend throughout the entire length of the amber piece. There are "major" strands (1.5-2.0 micrometers in diameter) criscrossed with numberous thinner strands (0.5-0.7 micrometers in diameter). The web is adhesive, which we know because of the lepidopteran scales and other captured insects as well as the "variously sized viscid droplets." The viscid droplets are covered with aerial plankton (pollen, spores and dust particles), which suggests that the nephilid spider did not rebuild its web at frequent intervals. This would be a similar pattern of behavior seen in extant nephilids.

Yours in sometimes providing relevant information,

Chelsea

Sources

"Fossil of Ancient Spider Attack Only One of its Type Ever Discovered." OSU College of Science. 8 October 2012. <http://oregonstate.edu/ua/ncs/archives/2012/oct/fossil-ancient-spider-attack-only-one-its-type-ever-discovered>.

Poinar, G. & Buckley, R. 2012. Predatory behaviour of the social orb-weaver spider, Geratonephila burmanica n. gen., n. sp. (Araneae: Nephilidae) with its wasp prey, Cascoscelio incassus n. gen., n. sp. (Hymenoptera: Platygastridae) in Early Cretaceous Burmese amber. Historical Biology. 24(5): 519-525.