Larval Numbers: Update

Although the 'egg lay' has been huge (i.e. the females weren't sitting around watching daytime TV and painting their fingernails, but have laid a lot of eggs), it is clear that there has been an unusually high mortality rate amongst 1st instar (= baby) larvae.

In and around Savernake, and elsewhere, we have recorded a 1st instar mortality rate of about two-thirds, from a decent sample.  

This means we are finding a lot of 'L1 Fails'; i.e. single leaves bearing the distinctive feeding marks close to or, better, either side of an end-of-leaf larval silk pad + isthmus. Like this - 

Here's one with the egg case (by my thumb, the vacant seat pad is to the right, and has shrivelled) -

Often, the seat pads aren't that distinctive, or the feeding isn't, in which case you need to find the egg case base (or ECB for short) to be sure. 

I have not recorded a higher loss rate amongst L1 (1st instar) larvae, though L1 losses were high in the thundery heat of 1976. 

It looks as though a great many of them succumbed to the heat, and desiccated. Some, though, will have been predated, though invertebrate predator numbers seem to be relatively low, again due to the heat (I can't monitor invertebrate predators, it's too difficult). E.g. social wasp numbers crashed in mid-July.  

We have even lost some early 2nd instar larva to assumed heat desiccation. I have not recorded this before, though Dennis Dell has in Switzerland, which is prone to hotter weather. 

However, we haven't lost any young larvae to heavy rain wash-off, which happened in 2018, and even in 1976. We haven't had any thunderstorms. (L1 larvae are vulnerable to thunderstorms).

All this may mean that predation by titmice during the winter may be lower than it would have been...

Here's what we like to find, a healthy L2 (2nd instar) 'pillar -

I have also recorded Savernake's earliest ever 3rd instar larva (L3), on August 14th.  

Finally, sallow foliage quality is wonderfully high this year, without any of the Willow Rust which rampaged throughout the western reaches of the Empire during 2023 and 24, and hardly any Sallow Mildew (another problem, in damp summers). 

This does mean, though, that there's an awful lot of foliage to be searched...

Onward, towards the 2026 Purple Emperor season!