Thursday 27 August 2009

More Nematus pavidus hatching

The batch of eggs that I showed yesterday is in the process of hatching:


A couple of things are worth mentioning, here: Firstly, sawfly larvae (in common with moth and butterfly larvae) go through a series of skin moults, after which they may change colour. These different colour forms are called 'instars'. The instars may vary in colour and/or in pattern, leading to some difficulty in identification, since all instars need to be known for a positive identification in each case. Some of the sawfly larvae in the above image have just started to eat and have turned green, the expected 1st instar colour for this species. The larvae which have eaten only the eggshells are still pale and are really instar 0 larvae.

Also note the marks (top left) where the eggs were attached. These indentations are used to anchor the eggs, and are made by the modified ovipositor, or saw, of the female, which gives rise to the name 'Sawfly'.


Despite the more-or-less continuous rain, a few moth species are still coming to light.


This is Lesser Yellow Underwing - Noctua comes - and is new to me.


And this is Dark Marbled Carpet, which I see every year.

8 comments:

Gill said...

How long do the eggs take between laying and hatching?

Now seems quite late in the year to be starting your life-cycle (unless this is a second brood).

Stuart said...

I'd say a couple of days at the most.

Interestingly, I think they are double/multi brooded, but not in the location that I've been documenting: I find them much earlier in the year at another location (my garden), but in this location it's always August/September. The larvae will be fully-grown in 3/4 weeks time, then they will hibernate, so plenty of time.

Stuart said...

Addendum:

A little bit of further research shows that the Chalcid family contains the smallest insects known. Dicopomorpha echmepterygis is only .139mm long - smaller than a single-celled paramecium. So the Chalcid shown is a giant.

Gill said...

"Dicopomorpha echmepterygis is only .139mm long - smaller than a single-celled paramecium." Good grief! And how many cells does it contain I wonder - they must be truly minute - makes you wonder how the cell machinery - mitochondria and so on - can work at that scale. And moving through the air must seem like treacle!

I not too that "smallest insects known" - you do wonder if there might be some even tinier ones that are unknown. I wonder what the theoretical smallest insect can be (and indeed tha largest)? Nature never ceases to amaze and delight me.

Stuart said...

In terms of the smallest, the male never sees fresh air: it spends its entire life inside the egg of a Psocid.

I seem to remember that theory says the largest beetle can be 6" long....

Yes...

http://www.public.asu.edu/~icjfh/edu/trachea/TS_Giants3.html

Which extrapolates the maximum size to be 6.7": exactly the size of the world's largest beetle.

Gill said...

"In terms of the smallest, the male never sees fresh air: it spends its entire life inside the egg of a Psocid" Good lord! How does he find a female, or she him?

I guess some of those fig wasps that never leave the figare similarly tiny?`

Stuart said...

Err, he hatches from the same batch as his sisters and mates with one of them.

Gill said...

"Err, he hatches from the same batch as his sisters and mates with one of them." Yikes - so there is room inside one phocid egg for a whole batch of mini-insects?!

[How on earth were these things first spotted - you'd have to be looking very carefully!]