# Armoured Lepidopteran Caterpillars Preserved in Non-Fossil Resins and What They Tell Us about the Fossil Preservation of Caterpillars

## TL;DR

This study reports two rare, hairy caterpillars preserved in non-fossil resins from Brazil and Madagascar, offering new insights into how caterpillars are preserved and the terminology used for resin types.

## Contribution

The paper introduces two exceptionally preserved, long-haired lepidopteran caterpillars in non-fossil resins and clarifies terminology for resin preservation.

## Key findings

- Two lepidopteran caterpillars with prominent hairs and spines were preserved in non-fossil resins from Brazil and Madagascar.
- The specimens increase the known size range of resin-preserved caterpillars to over 12 mm.
- The study highlights the rarity of hairy caterpillars in resin preservation and the importance of detailed imaging for morphological analysis.

## Abstract

Some trees produce a plastic-like product called resin, which when fossilized is called amber. In this study we comment on the current terminological difficulties regarding the description of fossil, non-fossil and so called “sub-fossil” resins. We furthermore report two long-haired lepidopteran caterpillars in resin from Brazil and Madagascar. It is likely they represent larvae of Erebidae (tussock moths and others) which typically have long hairs and spines. Long-haired caterpillars are exceptionally rare in amber with only one similar specimen to date, as most other caterpillars in resin are either “naked” or have a protective case. These new specimens also increase the known size range of caterpillars preserved in resin to up to 12 mm. We also emphasize the importance of images when describing and publishing caterpillars in resin, to allow broader morphological studies using all available specimens.

Resin is a plastic-like product of trees. Older occurrences of such resin are referred to as amber and are considered fossil resin. Younger resins are termed copals. Even younger ones have been dubbed defaunation resins. Non-fossil resins remain in a terminological limbo, often referred to as “sub-fossils”. We report two lepidopteran caterpillars preserved in non-fossil resin: one from Madagascar, one from Brazil. Prominent hairs (=setae) and spines (=spine-like setae) of the specimens make it likely that they represent larvae of Erebidae (e.g., tussock moths and others). So far, most known caterpillars preserved in resins are either “naked” or bear protective cases; only few are armoured with spines or hairs. In particular, long-haired caterpillars such as the ones reported here are so far almost absent. Only one specimen with comparable setae has been reported from 15-million-year-old Dominican amber, but no significant details of this specimen are accessible. We briefly also review the record of caterpillars known from the Holocene, recognising that it is very sparse. The new specimens demonstrate that very hairy caterpillars can readily be preserved in resins in fine detail. Furthermore, the specimens increase the known size range of caterpillars preserved in resins, with one measuring more than 12 mm.