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11 June 2015

11 June 2015 – Rejectamenta and other Excrementitious Matter

December Moth (caterpillar)

Swirling mists and heavy dew this morning, following what is supposed to be the warmest night of the week.  Very little moth activity – Poplar Hawk-moth, Clouded-bordered Brindle, Silver-ground Carpet, Pale Tussock, White Ermine and a cockchafer.  

In the absence of mature creatures, step forward the December Moth caterpillar for a closer look.

Caterpillar and hawthorn

The eggs were laid on 3 November 2014 and the first caterpillar emerged on 23 April 2015. Not all the larvae emerged at the same time and there are different stages of development in the breeding container.  When first hatched the larvae produced lots of silken threads and could be seen dangling rather pointlessly. Perhaps they disperse in this way.  After the first instar the larvae remain stock-still all the day having chosen a leaf stem upon which to stretch out their full length.  They vary slightly in colour but merge well with the hawthorn – the food plant – and tend towards lethargy.  They are quite slow and ponderous in their movement.


Frass.  From the German fressen – to devour.  H F Stainton first used the word in 1854 : the half-eaten leaves attest but too surely that some devourer is near.  These indications of the presence of a larva are expressed in the German language by the single word ‘frass’, and we may, without impropriety, use the same word for the immediate effect of the larva’s jaws, and the more indirect effect of the excrementitious matter ejected by the larva.

E A Adams (1860) refers to frass as ‘the rejectamenta found at the entrance of the burrows of wood-boring insects’.The photograph above records one night’s mass of frass as produced by the 20 or so caterpillars.

Silver-ground Carpet (Xanthoroe montanata)

A pleasingly beautiful image to refresh our sensibilities…

May Highflyer (Hydriomena pluviata)

The two moths depicted above are not new.  The Silver-ground Carpet is there purely because it is a particularly handsome specimen with exquisite patterns and colours.  The second moth photograph is by courtesy of Alison Turnbull who trapped this May Highflyer in Norfolk and it will serve very well as a replacement for the one I missed photographing on National Gardens Scheme night.  

We have another identification evening coming soon (19 June) so do come along if the weather is good.  The gardens look splendid at the moment.Total species count now stands at 362.