Welcome to my blog

This is where I post various musings about wildlife and ecology, observations of interesting species (often invertebrates)
and bits of research that grab my attention. As well as blogging, I undertake professional ecological & wildlife surveys
covering invertebrates, plants, birds, reptiles, amphibians and some mammals, plus habitat assessment and management
. I don't work on planning applications/for developers. The pages on the right will tell you more about my work,
main interests and key projects, and you can follow my academic work here.

Tuesday 23 April 2013

Pondnet diary day 1

Pondnet is a new Pond Conservation volunteer survey aiming to identify trends in pond quality and associated species. I was recently allocated a pond in Milkmead Copse in Hampshire's Itchen Valley Country Park, and now spring's arrived, I decided that today was a good opportunity to make my first visit to the site.

The pond in Milkmead Copse
It was good to see some frogspawn had survived the cold conditions as there were at least a couple of hundred recently hatched tadpoles, plus one adult newt. However, something else (yup, an invertebrate) caught my eye - a water scorpion (Nepa cinerea) that came to the surface.
Water scorpion, Nepa cinerea
This is a predatory true bug (Hemiptera) and the raptorial (hunting) front legs used to grip prey are clearly visible, plus the breathing tube at the rear. Although this appears to be a single thin tube, it is actually formed from two halves (they separate if a specimen is dried) - air flows from it along two grooves which have small water-repellent hairs and the spiracles open into these grooves (Denton, 2007). Being a bug, it has piercing/sucking mouthparts rather than the jaws/mandibles seen in beetles. It is a large insect by UK standards at around 20mm in length, excluding appendages. It is an active hunter, taking small fish and various other invertebrates. However, I was surprised to see it tackle a larger (approx 25mm) dragonfly nymph, itself an active and powerful predator.

N. cinerea attacking a dragonfly numph.
N. cinerea on the back of the dragonfly nymph
This is not behaviour I've seen before and the nymph struggled for a few minutes before managing to dislodge its attacker by dragging it against a piece of vegetation. Presumably the position of N. cinerea allowed it to pierce the nymph while remaining out of direct reach. Certainly, the water scorpion swam away after this encounter and the nymph came back to the surface. I'm not 100% sure which species it is as it is coated in silt which obscures key features. However, the size, head shape and silty coating are typical of the black-tailed skimmer (Orthetrum cancellatum) so that is my identification for now.

Dragonfly nymph, possibly Orthetrum cancellatum, the black-tailed skimmer. Note the hairs on the legs and body, coated in silt.

The same dragonfly nymph - note the protruding eyes and the 'mask' showing the mandibles.
So, an interesting start to a new survey programme. More to come from the pond!


Denton, J. (2007). Water Bugs and Water Beetles of Surrey. SWT, Pirbright.

No comments:

Post a Comment