A "spider rider" in Baltic amber

Fund proves existence of exceptional behavior 44 million years ago

Sackspider in Baltic amber with the larvae of a fang, which holds itself in a typical position on the back of the spider © Michael Ohl / MfN
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A Berlin researcher has discovered an insect larva in Baltic amber that feeds on spider eggs and piggybacks on a spider until it builds a cocoon. The special find shows this extraordinary behavior for the first time in fossils and shows that it was created more than 44 million years ago.

Catching Mantis or Mantispidae are an exotic group of neuroptera that look like little praying mantids thanks to their forelegs. However, this similarity is only superficial and a perfect example of multiple evolution of similar organs - researchers speak of convergence.

Larvae with unusual behavior

Most of the catching larvae show a very unusual behavior. These feed exclusively on spider eggs or spider larvae, which they suck in the cocoons of wolf spiders and relatives.

In order to find such cocoons, some catch fish use a special strategy: The first-larvae are very agile and, according to the scientists, manage to climb a female Wolf Spider. On board the spider, they remain until it spins a cocoon into which the larva then penetrates. Then the spider meal can begin.

Euclimacia horstaspoecki, a today living catch from Thailand. © Sören Materna

Grubby and fat

The later larval stages of the Fanghaft are then maggot-like and eat fat until pupation. Such spider-bearing larvae of fishes can even survive the skinning of spiders by retreating into the book lairs of the animals and waiting. display

Michael Ohl from the Museum of Natural History in Berlin has now succeeded in proving such a "Spider Rider" in Baltic amber. The snake's larva sits on the back of a sack and waits for the spider to build a cocoon.

A still unwritten Fanghaft from Burma. O Michael Ohl / MfN

First fossil larva of a catching species

According to the researcher, this find is not only unusual because it is the first fossil larva of a catchy species at all, but also because it provides direct evidence of the existence of a special behavioral strategy 44 million years ago. Normally, fossil behavior is difficult to detect. (Natural Sciences, 2011; DOI: 10.1007 / s00114-011-0783-2)

(Museum of Natural History - Leibniz Institute for Evolutionary and Biodiversity Research at the Humboldt University Berlin, 06.04.2011 - DLO)