The moth-mummy returns

I've written about parasitic braconid wasps before, and you know, I probably will again - because they are fascinating. This one hatched recently from the mummified remains of what I think is a small noctuid moth larva that I found in our garden, possibly one of the Xestia or Noctua species.

Mummified remains of an unfortunate moth larva, showing the legs

Mummified moth larva showing the wasp's exit hole at the rear. The material sticking the mummy to its substrate can be seen beneath the head.

As you've gathered, this is an internal parasite (parasitoid) - in this case probably Aleoides borealis or something taxonomically close to it (written as "Aleiodes sp. near borealis"). This kills the host before it is fully grown - it then changes the host behaviour to ensure it adopts a parasite-frindly position, after which the parasitoid makes a slit in the host on the underside near the head. Through this slit, it produces a sticky fluid which glues the host in place. However, I don't only have an empty husk to show you - I collected the mummy before emergence, and this is what appeared in my hatchery.

Aleiodes sp. near borealis

Head (with ocelli) of Aleiodes sp. near borealis

Abdominal pattern of Aleiodes sp. near borealis

Parasitic Hymenoptera are notoriously tricky to identify, but I think this is a reasonable conclusion - as ever, I am happy to hear from anyone who has a better idea what it is!

Red goo of doom

If you've seen and/or read H.G.Wells' War of the Worlds, you'll know about the alien red substance that creeps and raminates... if not, I recommend a library near you. In any case, when I saw a fairly uniform red growth in water on a polythene cover in our garden, (a) my sci-fi nerdery kicked in, and (b) I had to see what it really was.

Mystery red goo in a thin layer of rainwater.

 I did wonder if it was bacteria, and took a sample for a look under the microscope.

At x40, small round red structures are seen.

At x100, these show some faint internal structure.

Using the camera to zoom to about x250, this creature was seen, alive but contracted.

At this point, I knew that is wasn't bacteria (well, I'm sure there is some too) but a rotifer, probably Rotaria sp. These can be found in mud, detritus, among moss and in free-standing water as here. If their thin layer of water dries out they can form resistant cysts and re-emergence when wetted by rain - it is possible the red structures are cysts as rotifers can be very numerous. Rotifers as a whole are small (almost all smaller than 1mm, and some a tenth of this) and found in almost any wet or damp habitat. Some genera are benthic/littoral, some are planktonic, many include both benthic and planktonic species. Most rotifers seen are female and reproduce parthenogenetically (i.e. without needing to mate), while males occur sporadically and often seasonally, and being smaller are less often found. However, males are not known for the bdelloid group in which Rotaria is placed. So, presumably the photos here are all of females!


There isn't space for a detailed look at rotifers here, but if you want to be able to identify British freshwater planktonic species (e.g. those found in ponds), then Pontin (1978) is a good starting point.

While some move with cilia, others, as here have a 'foot' like a mollusc and move using this, being able to contract and expand their body.

Rotaria extended and curled. Various structures are visible - the head is blurred bottom-right - moving left, the paired jaws can be seen.

Rotaria extended, head towards the bottom.

Next post - back to the macroscopic world!

Reference

Pontin, R.M. (1978). A Key to the Freshwater Planktonic and Semi-planktonic Rotifera of the British Isles. FBA, Ambleside.

Orange agents of decay

While checking a bee-log in our garden, I noticed one of the holes had a dead fly in it. I removed it and was about the throw it away when I saw tiny orange dots on the surface. Because I am a nosy ecologist I put it under the microscope to see if there was anything interesting going on, and saw what looked like a microfungus growing out of the joints and bristle-bases of the fly.

Fly (possibly in the family Muscidae) with orange fungal growths.

There are some very interesting fungi that parasitise insects and I've written about one of them before. However, this looks different - maybe something simply using an already-dead fly as a substrate.

Fungal growths showing the thin threads of hyphae between the orange fruiting bodies.

Fungal fruiting bodies at the bases of the fly's bristles.

The fungal structure is clear - hyphae and fruiting bodies - but with most microfungi, it is necessary to look at the spores, so I made a slide and zoomed in.

Fungal spores x100

The spores are clearly visible as slightly curved spindles, each split into several sections by cross-walls (septae). However, though a mycologist would probably know this fungus by sight, I couldn't find anything that matched it, so sent my pictures to the British Mycological Society's facebook group. It didn't take long for one of the BMS to tell me that this was a species of Fusarium. This at least explained why I hadn't worked out what it was - most Fusarium species are soil fungi involved in decomposition of dead organic matter but I hadn't been looking at soil-dwelling species. If so, the fungus was simply decomposing the fly - which is what it does, and very usefully too; no soil decomposers = dead soil. However, some Fusarium are insect (and plant) pathogens, so it could have killed the fly before decomposing it.

Fusarium are varied, diverse (in terms of both species and strains) and not all well understood or taxonomically clear, though some cause plant diseases and others can infect humans, while one is the main ingredient in Quorn! So, the identification stops at genus on this occasion, but has introduced me to a fungus that, although I'd heard of it, and it may be growing all around us in the ground, I've never stopped to look at before. Thanks BMS!

Beetles love big butts and they cannot lie

Spring means many things - for many species overwintering adults re-emerge and set about the important business of reproduction. One common species that is often seen doing this is the green dock beetle Gastrophysa viridula. It feeds mainly on broad-leaved dock Rumex obtusifolius and related species and in April/May patches of dock can be seen with large numbers of these beetles. Such groups can be highly localised however - one patch of dock can have hundreds of beetles while a nearby patch on the same site seems to have none, possibly due to adults clustering for mate-finding purposes - it is not due to mobility as they can fly. Mating is a competitive activity though as males may try to dislodge rivals, and have foot-pads. These appear white around the sides of the tarsi (feet) to help them grip the female.

Two male G. viridula compete for one female.

Gastrophysa viridula as they are often found - a mating pair.

A dislodged male G. viridula draws its legs in for protection.

The females are particularly distinctive as they have swollen abdomens which extend beyong the elytra (wing cases). There are two or more generations per year (possibly up to six depending on temperature and other conditions) and the oval yellowish eggs can be seen in small clusters. The first new adults emerge in June and others appear through to September. They then overwinter from October to April.

Eggs of G. viridula.

Female G. viridula showing the swollen black abdomen.

The adults chew roundish holes in dock leaves, but the black larvae can skeletonise whole leaves until just a network of veins is left. For this reason, where certain Rumex species are considered invasive, G. viridula has been suggested as a potential biological control, though as ever introducing non-native species needs to be considered very carefully to avoid unwanted impacts on native species.

G. viridula larvae feeding on dock leaf.