Stinky sticks

I keep black beauty stick-insects, Peruphasma schultei which hide, not by looking like vegetation but by being black, velvety (hence non-reflective) and nocturnal. However, although usually calm when handled, they do have active defences which I discovered recently when retrieving a large females that had escaped to climb the curtains. I felt something wet on my hand, and when I looked there was a milky, eye-wateringly acrid liquid. I knew that a lot of stick-insects can spray defensive chemicals but hadn't witnessed this one before. Fortunately a quick Google told me that this had been investigated by Dossey et al. (2006), who discovered a new defensive compound that they named 'peruphasmal' after the insect producing it.

Peruphasma schultei

Peruphasmal is an isomer of dolichodial, a compound in the iridoid group.

structure of dolichodial

Iridoids are found in many plants (usualy in the form of glycosides) and may be active ingredients in those used medicinally. They are also likely to have a defensive function, protecting the plant against herbivores. Dolichodial and its isomers are found in plant essential oils, and as in this case, in the defensive sprays and secretions of some insects, possible being sequestered from food plants, or being produced by the insect's metabolism (they are intermediate compounds in the production of alkaloids for example). My P. schultei are fed on privet (Ligustrum sp.) which is in the family Oleaceae, one of those known to produce iridoids, so sequestration is plausible. The toxin in Ligustrum appears to be the glycoside syringin, known originally from lilacs, but now known to be a white, crystalline, bitter toxin in many plants including privet, hence its alternative name 'ligustrin'. So, this is a likely candidate for the source of the insect's defence. In plants, iridoids are usually bound to glucose, and peruphasmal is also sprayed along with glucose. Whatever the source - there is more research, but not much - it is an effective defence; my reaction was to put the insect down and wash off the secretion - a predator would have been sprayed in the face...



References

Dossey, A.T., Walse, S.S., Rocca, J.R. & Edison, A.S. (2006). Single-insect NMR: a new tool to probe chemical biodiversity. ACS Chemical Biology 1(8): 511-514.

Bioblitz 2 - The Hatching

Earlier in the summer I helped out with identification at a bioblitz, and one of the things I was given to look at was a cluster of pupae attached to an oak leaf. It didn't take long to work out that they were a species of small parasitic wasps in the genus Eulophus, but they needed to be reared to adulthood to be identified to species. So, that's what I did...

Now empty, the ring of pupae that surround the host caterpillar (removed), giving this stage of Eulophus the name 'tombstone pupae'.

Side view of Eulophus - note the metallic green colour, much reduced wing venation and long pale legs. The body, excluding legs, wings and antennae is around 2mm long.

Note the bulges on the mesoscutum just in front of the wing bases. The line around the bottom of a bulge is called the notaulix (pl. notaulices) and is only sharp in the front half. This is diagnostic of the subfamily Eulophinae.

The antennae are inserted level with the base of the eyes, not halfway up. This is one characteristic of the genus Eulophus.

The scutellum (the upper surface between the wing bases here) is only slightly convex, not strongly bulging. This is another characteristic of Eulophus.

More characteristics - the front coxae (basal segments) are pale and the mid coxae are metallic.

These (and some other hard-to-photograph) features mean that this species is Eulophus larvarum. It is common in the UK and has two forms - the spring form (April-June) and the summer form (June-August). The summer form has a pale spot near the front of the gaster (the broad or 'main' part of the abdomen) which is seen here.

The pale/yellow spot on the gaster showing this to be the summer form of E. larvarum.

This species is a parasite of the exposed caterpillars of moths in several families in the UK. Being so tiny they are often overlooked, but careful searxching may produce specimens and they were easy to both raise (in a  ventilated lidded pot) and (to my surprise) identify, using Askew (1968) which is now available as a free download - see below.


Reference

Askew, R.R. (1968). Handbooks for the Identification of British Insects 8(2b). Hymenoptera: Chalcidoidea Section b. RES, London. [free download here]

Bioblitz bits AKA things in other things

I've done a couple of bioblitzes as entomological geek-in-residence for the day, identifying things that are a little tricky, and the most recent was just a couple of days ago in Southampton, around the Southampton University campus. This involves me looking for specimens myself, but during busy periods such as when groups come back from recording sessions, I'm at a table with a microscope and a pile of books. A lot of different species passed through my hands that day, but here are a couple of less familiar one that are both endoparasites...

The species of interest here isn't the aphid, but the disc-shaped structure below it. The aphid is a mummified husk at this stage because it has been parasitised by the small wasp Discritulus planiceps. This lives inside the aphid, then exits through the body wall and develops into an adult inside the disc-like cocoon it builds beneath the host skin. Wasps of the genus Praon do something similar but their cocoons are tent-shaped.

This cluster of pupae was attached to the underside of an oak leaf. They are each a few millimetres long and have small blobs of what I assume are dried faeces at one end. A bit of research indicated that they are probably wasps of the genus Eulophus. They are now in my hatchery to see if I can confirm the species once they emerge. They will have emerged from a caterpillar host before pupating and the fragments to the left of the cluster are probably where it was attached before falling off the leaf. A more familar species is the braconid wasp Apanteles glomeratus that has a similar lifestyle, parasitising the caterpillars of white butterflies like Pieris.

A close-up of a Eulophus pupa - various structures are quite clearly visible such as eyes and mouthparts.

At the end of the day, Lizzy from HBIC announced the total number of species recorded on the day - 257, an increase of about 30 on last year's event, although more records will trickle in a specimens like the Eulophus above are identified.

Smelly, slimy and slithering

We have a wildlife-friendly garden, and part of that is a pesticide-free compost heap. When it needs to be turned over, the usual creatures are plentiful - earthworms, slugs, woodlice and so on - but sometimes something less familiar appears, brought to me by my loving wife...

A mass of about 20 worm-like creatures attached to a decaying slug.

I usually deal with invertebrates with legs, but I like a challenge so, holding my nose (the slug-remains were highly fragrant!) looked more closely.

One of the 'worms' off exploring.

It was clear very quickly that these weren't leeches. Although they moved like them, they didn't have the segmentation or mouthparts - instead they were a type of flatworm. A quick look at Jones (2005) told me they were Kontikia ventrolineata, an Australian species introduced through the ornamental plant trade.

Kontikia ventrolineata - the pair of grey lines on the dorsal surface is a key identification feature.

Kontikia ventrolineata - the series of light and dark bands on the ventral surface is another key identification feature, and give it its specific name.

The garden plant trade has introduced several Australasian flatworms to Britain,and some such as the Australian flatworm Australoplana sanguinea and the New Zealand flatworm Arthurdendyus triangulatus can be problematic as they are predatory and hunt earthworms, and may impact on populations of our native species which are so important for soil quality. Fortunately K. ventrolineata is probably less troublesome as it feeds on small snails and possibly slugs, as well as (in this case) scavenging. As yet, I am unaware if it has an impact on our native molluscs, though it is widespread in southern and southwestern England (and as I understand it has been found as far north as Scotland, although the NBN currently holds no records). So, observations and data are always welcome, and if you see this species in England or Wales, let Hugh Jones know via the Natural History Museum in London (scroll down, he's a Scientific Associate), or in Scotland, you'll want Brian Boag who works on introduced and invasive species.

Reference

Jones, H.D. (2005). Identification: British land flatworms. British Wildlife 16(3): 189-194.

In spring the pond goes sproing

After a long, cold early spring, the last couple of weeks have been warm, dry and sunny - and the season has leapt at the opportunity. Butterflies are flying, birds are nest-building, bees are pollinating. All good things. As a microcosm of this rapid seasonal burst of activity the denizens of our garden pond have been distracting me from computer-based tapping and drawing me out to sit by and watch, camera in hand. Our pond's not huge, but a lot of care was taken to ensure variety of structure (and thus habitat) - here are a few of the occupants taking advantage of it.

The fly Elgiva cucularia. It is a member of the family Sciomyzidae that specialise in hunting snails - of which we have plenty. This species is associated with boggy conditions and I have recorded it several times on our pond vegetation, so the shallow, algae filled section is clearly doing its job.

A Large Red Damselfly Pyrrhosoma nymphula posing obligingly on my finger.

One of at least six smooth newts living in our pond. This shot was taken with a waterproof endoscope which I'm still new at using.

Some of this year's batch of frogspawn.

Two pond snails busily engaged in making more snails. The whitish structure top-right is indeed a snail penis AKA 'love-dart'.

Unexpected egg-flies

Back in January, my wife showed me a blackbird egg she'd found in the garden. It looked whole, but was incredibly fragile and broke almost as soon as I picked it up, clearly already being cracked. I expected maybe a whiff of something nasty, but there was more going on than I expected...

Inside the egg... lots of invertebrate action.

Naturally, instead of saying 'yuk' and throwing it away, I had a closer look. The orange inveretebrates are mostly fly pupae plus a few larvae. The black shapes are pupal skins of something already emerged, and the large larva in the middle something else entirely. A quick look in Smith (1989) jogged my memory that the smaller ones were probably juveniles of the Psychodidae, also known as moth-flies or owl-midges. The larvae of many species are associated with decaying organic matter, so the inside of a failed egg is a plausible hiding/feeding place whether the goo insode is egg material or something else that had seeped in. Beyond that I couldn't tell, so I put them in a hatchery and waited. After not too many days this is what I found...

Pupae, pupal cases and adults of a psychodid fly.

In total there were 15 pupae and these soon started to emerge as adults. The small size, their shape, and their hairy/feathery wings mean they don't look like typical flies, but that is exactly what they are - as you can see below, they have a single pair of wings, the other pair reduced to drumstick-shaped balance-organs (halteres). Psychodidae are not an easy group to work on (especially if you are not that familiar with them), and identifiying the flies to genus, let alone species, would require time, a microscope, and a copy of Withers (1989). I won't go through all the steps, but here are a few key features:

There are two veins (dashed lines) between the two main forks in the wing veins (circled).

The arrow indicates the eye-bar - an extension of the eye above the antenna. The circle indicates the pale haltere mentioned earlier - yes, these realy are flies!

 The antennae are an important feature too, but take care when keying out genera and species...

The key asks whether the antennal segments are barrel-shaped or have an elongated stalk. These look barrel-shaped but...

...if you remove a segment you can see that the barrel-shape in this case is formed of hairs that hide the real shape - the dark segment clearly has a stalk.

So, after quite a bit of deliberation, this keyed out as the genus Psychoda. I'm less certain about the species (not only can they be difficult to separate, but the taxonomy of Psychoda needs to be revised), but it might be P. alternata (the stripy larva in the first photo matches this, as does the foul habitat). Withers (1989) doesn't list Hampshire for this species, but the Psychodidae are under-recorded, and he does mentioned Wiltshire and Sussex, so it wouldn't be a surprise. That's enough for now - I shall leave you with some more juveniles, feeding/hiding merrily in the goo...

Psychoda - three pupae (complete with a pair of pupal horns for breathing) and a larva.

References

Smith, K.G.V. (1989). An Introduction to the Immature Stages of British Flies. Handbooks for the Identification of British Insects 10(14): 1-280.
Withers, P. (1989). Moth Flies. Diptera: Psychodiae. Dipterists Digest 4: 1-83.

Ghosts in the shell

You probably don't know, but I have a pet giant African land snail (Achatina fulica) called 'Chickpea' because that's what s/he (the species is hermaphrodite) looked like when young. S/he's now a bit larger and 'Brazilnut' might be more accurate.

Chickpea the not-yet-giant African land snail.

However, the keeping of exotic invertebrates is not today's topic. While cleaning Chickpea's tank, I noticed some tiny white dots moving rapidly around the snail's foot and disappearing behind it. Of course, I grabbed a camera and then went online. It didn't take long to find out that this was an infestation of Riccardoella mites, probably R. limacum.

Riccardoella mites.

More Riccardoella mites.

I use the word 'infestation' because these are parasitic. They were previously though to be commensal, feeding harmlessly on mucus, but are now known to be blood-feeders. This may not be too much of a problem unless they are numerous, but their feeding can lead to secondary infection via the tiny wounds. They are also difficult to remove as they are very swift and hide in the pneumostome (breathing pore). Rinsing the snail with water is likely to help limit them, and if lucky may remove them all eventually, but the only other known option is to buy the predatory mite species Hypoaspis miles which will target them, although these mites are only available in large quantities for use across whole gardens, allotments and so on up to larger scales. It is likely that the mites came in with the soil used in Chickpea's tank and they are common in the wild, being found on various native slugs and snails. So, I will see if washing works, and if not, maybe a 'mite-share' scheme will do the job. Until then, I don't have access to electron microscopy, but if you'd like more info and some excellent images, I recommend this page.

Focusing on the familiar: butterfly wings

It's a while since I've written anything (workload, the evil flu of doom etc etc), so I thought I'd resume service with a look at something that everyone's at least broadly familiar with, even if not in detail - butterfly wings. You may know that the insect order Lepidoptera (butterfles & moths) means 'scaly wing', and that's because the wings are covered in many tiny scales that effectively work like pixels to make up the overall pattern.In December a very fresh looking peacock butterfly Inachis io was roosting in our house, presumably hibernating, so I took a couple of pictures.

Peacock butterfly Inachis io

One of the 'eyes' in the wing pattern - individual scales are clearly visible.

Near the base and front edge of the wing - again you can see individual scales.

I could put the wing under a microscope and get more detail, but I didn't want to disturb the butterfly while it was roosting - instead, there is a light microscope image here, and electron microscope images (which I can't produce!) here (x1000) and here (x5000). The last one is important becuase it shows one way that scale colours are formed.

Browns and blackish colours are formed by melanin pigments in the scales - the same type of pigment that we have in our skin, hair and the irises of our eyes. However in most cases the brighter colours - reds, greens, blues and so on - occur because of iridescence caused by the microstructure scattering light in different wavelengths depending on the precise fine structure. If you have a microscope, the scales brush off easily without damaging the wing (you could use a small soft paintbrush then transfer them to a slide) so why not have a look at the scales - if you don't want to disturb a live butterfly or moth, you can wait until a dead one turns up. Happy scaling...