Aboard a spider--a complex developmental strategy fossilized in amber.

Mantid flies (Mantispidae) are an unusual group of lacewings (Neuroptera). Adults markedly resemble mantids in their general appearance and predatory behavior. The larvae of most mantispids exclusively prey on spider eggs, whereby the first instar larva is highly mobile and active and the other two larval stages immobile and maggot like. One of the larval strategies to pursue spider eggs is spider-boarding. Here, I report on the first record of a fossil mantispid larva. It was found in Middle Eocene Baltic amber, and it is the first record of Mantispidae from this deposit. The larva is attached to a clubionoid spider in a position typical for most mantispid larvae, and, thus, it is also the first fossil record of this complex larval behavior and development.