An oak eggar moth caterpillar photographed in England in November
by Stephen Hewitt | Published 20 May 2022
The photographs in Figures 1-3 here show a hairy caterpillar with black, orange and blue rings around its body found on brambles in a hedge in the countryside of Cornwall in November 2021. Along its back were bright, almost white markings, pointed like spear heads, seen in detail in Figure 3.
This is an oak eggar (Lasiocampa quercus) moth caterpillar, an identification I made by using information that was on the following websites in May 2022.
In May 2022 this site had photographs of hundreds of different moths and caterpillars. There were images of caterpillars identified as oak eggars on several pages, including the following.
This page stated: “When using the caterpillar galleries it's worth bearing in mind that some caterpillars dramatically change their appearance as they grow. With each skin moult they can suddenly look very different.”
It then used the oak eggar as an example of this, with three photographs of successive stages of development, showing the oak eggar caterpillar's changed appearance. The photograph  of the earliest stage, labelled as second instar, looked like the caterpillar in here.
Another page with images of caterpillars identified as oak eggars was the following.
This page reported the sighting of two oak eggar caterpillars in Cornwall in November 2012 and stated: “The smallest of the two caterpillars, about 20mm was sporting the dramatic orange diamonds of a second instar caterpillar about to hibernate.” The accompanying photograph  looked similar to the caterpillar in Figure 1.
On this page, a poster in a forum reported over a time period of 19 months the rearing of a caterpillar into an adult moth. The posts included photographs. The earliest photograph of that caterpillar  showed its appearance was like the one photographed here, and the moth  that finally emerged from a cocoon looked like an oak eggar.
A pocket guide with no information
In contrast to the websites, a pocket book that did not help identification was Concise Butterfly & Moth Guide, New Holland, 2010, ISBN 978 1 84773 602 4. In the entry for the oak eggar it reports only “Larva is hairy and dark brown with black rings”. (Page 118)
The anonymous author(s) of this book do not use the word “instar” or mention the possibility of a caterpillar changing its appearance during development. Under the heading “The Life Cycle” the introduction states only “Caterpillars moult four or five times during their life”. (Page 8) A few lines later, for the development of the pupa, the introduction also states “inside, its tissues liquefy”.
On the front of this book is a black and white logo with the face of a badger and text “The Wildlife Trusts”. In May 2022 the UK government website at https://trademarks.ipo.gov.uk/ipo-tmcase/page/Results/1/UK00002452594 confirmed that this had been a registered trademark of the Royal Society of Wildlife Trusts. Inside the book there is no explanation of the book's relationship to that UK registered charity (number 207238).
- Photograph at http://www.wildlifeinsight.com/wp-content/gallery/gb_caterpillars/oak-eggar-caterpillar-early-instar-5114.jpg in May 2022 with SHA256 hash 7cf62a8f660314e007b9c34216cda03a8168bef0971aaab463098cd2da988dbf
- Photograph at http://www.wildlifeinsight.com/wp-content/gallery/gb_caterpillars/oak_eggar_moth_caterpillar_2nd_instar_5124.jpg in May 2022 with SHA256 hash a0850f271ac7786272a4f6a074f4431befe093bf6d51c55955769580b19d80bf
- Photograph at https://www.birdforum.net/data/attachments/209/209213-d6e8ea9eeab8ea7ecc9c101b89138274.jpg in May 2022 with SHA256 hash d7fd7e0496af8164b2103a5f77c9f8529d13c8b23d5a8f7dafe909017c5341f2. By joining the forum, I was able to see larger versions of the photographs than those on the public web page, the larger version of this one at https://www.birdforum.net/attachments/1637-oak-northern-eggar-jpg.234843/ with SHA256 hash 40952caf88e54ff0c7a918b9d3a8ff65ff9c9119798602de547997a6d1f5cff5
- When logged in, large version of photograph at https://www.birdforum.net/attachments/1637-northern-eggar-male-jpg.326212/ in May 2022 with SHA256 hash 05063fae75635982e94a98bb06250c6cb25c77db78a8959b33e0d9e1c526b55d
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