Little larvae that love leaves

As you may know, I specialise in leaf beetles (Chrysomelidae) and quite often get sent specimens to identify as I run the national recording scheme for this family. These are usually adults, but now and again juvenile stages which are more difficult, but also useful reference material, especially as I (eventually) intend to write a guide to their identification. Some months ago I was sent some larvae preserved in alcohol to see if I could confirm whether they were Chrysolina marginata. It took me a while to find the time for this (it's been a busy year), but here's the process.

Tube of preserved larvae.

Contents of the tube. The larvae are of different stages (instars) and the largest ones are around 7-8mm long. The anal proleg is visible (especially in the specimen top right) and this is a feature of Chrysolina.

Sensory structures on the head. There are no compound eyes, but in Chrysolina there are six ocelli (simple eyes) on each side of the head as indicated by green arrows, four in a rough square and two the other side of the antenna which is circled in blue. The segmentation of the small antenna is clearly visible, including the small segments/structures at its tip.

Side view of one of the larger larvae. The blue lines show the joints between segments. The green lines show sclerites (hardened patches) arranged in irregular rows.

The end of one of the legs, showing the tarsal claw. The inset shows that the outline (solid) has no protrusion at the base. This is a feature of C. marginata with some other species having a protrusion (dotted line).

Close-up of the body surface. Sclerites are shown in green circles. The pale blue arrows show intermediate secondary bristles with small dark patches at the base of each. Between these there are tiny dark dots of microsculpturation as shown within the dark blue outlines. This mixture of features is seen in C. marginata.

So, the combination of features, along with the keys in Marshall (1979) and Zaitsev & Medvedev (2009) confirms that these larvae are C. marginata - easier than larval identification often is, and provides information that is due to be used in a report later this year.

References

Marshall, J.E. (1979). The larvae of the British species of Chrysolina (Chrysomelidae). Systematic Entomology 4: 409-417.
Zaitsev, Y. M. & Medvedev, L.N. (2009). Larvae of Leaf-beetles of Russia. KMK Scientific Press, Moscow. [In Russian]

This is why I geek those beetles

If you are a regular here, you'll know I spend a lot of time peering closely at small invertebrates in order to identify them, like here. For those interested in taxonomy and morphology (like me), that can be an end in itself - I find small creatures fascinating and I like to know what they are. I geek them, and do so proudly - plus I'm a professional entomologist/ecologist so there's the academic-kudos and getting-paid aspects. However, there is more to it than that.

I have been asked more than once why we need to identify species - and it's a fair question; after all, the beetles don't care whether we can name them, and individual ones would probably prefer not to be fatally sampled for the greater good. However, without identification (which often requires a dead specimen), there can be no survey, monitoring or collection of distribution data; and without these, we don't know what needs conservation effort. In an ideal world, their habitats would be fine, biodiversity would not be threatened, and conservation (if needed given the previous points!) would have limitless funding. Sadly these things are very very much not the case. So, samples are taken, species are identified (along with date, location etc) and data sent to recording schemes/centres, or now added to online systems such as iRecord to be validated by hard-working volunteers such as myself...

Once the data has made its way to the recording scheme database, it can be downloaded, interrogated - in short, used. This could be for any number of purposes - planning, research, amatuer interest, and so on. However, during the winter of 2013/14 I was lucky enough to be contracted to use this data to write a status review of the Chrysomelidae (leaf beetles), the group I specialise in. This meant looking at the change in distribution of all the British species and allocating them to categories such as 'Least Concern', 'Endangered' and 'Vulnerable'. Thus, scarce and threatened species could be identified and highlighted with extra information focusing on these, such as summaries of habitats, distribution, threats and conservation measures. This is important as it will inform conservation efforts, survey work, policy decisions and other activities. It's also part of a wider project with different specialists covering their groups of choice such as Carabidae (ground beetles) and is a major update to status review work published in the 1990s (e.g. Hyman & Parsons, 1992) some of which is now considerably out of date.

I won't go into any more detail here, but if you want to look at the report, it's called A review of the scarce and threatened beetles of Great Britain: The leaf beetles and their allies and is free to download here along with data covering the key species.

Reference

Hyman, P.S. & Parsons, M.S. (1992). A review of the scarce and threatened Coleoptera of Great Britain 1. JNCC, Peterborough.

Floodplain meadows are the new amenity

Our local playing fields are, ecologically speaking, not much more than a green desert - heavily 'improved' amenity grassland with barely a 'weed' in sight. Or at least they were until last winter's ongoing storms caused a local river to burst its banks.

February 2014 - playing fields underwater.

The fields are part of a floodplain and are below the level of the surrounding river channels, some of which have been built up and were used as canals decades ago. The floods seem to have surprised a lot of people, though I'm never really sure why the term 'floodplain' isn't seen as self-explanatory. Anyhow, not all the local residents minded...

A colony of black-headed gulls soon moved in to use the unplanned wetland - other species such as mute swans were also regularly seen.

The fields are also a popular dog-walking location - the shallow 'lagoon' soon became a well-used destination for humans-and-canines as well as avians.

The water persisted for some months but of course dried up when warm weather came. After a hot summer, the ground flora was looking very different to the near-monoculture present only a year ago.

Tall herbs such as fleabanes competing with the grasses.

Meadow plants such as butterbur are already abundant.

Now, I appreciate that leisure is a valid use for playing fields, but this wetted area covers a minority of the total area and the site's use for football and rugby continues unaffected. The newly floral patch is not only popular with invertebrates, but also with walkers (with or without dogs) as a path has been mown around the edge. I hope that it will be left to develop as a 'wild' patch rather than being mown back to amenity grassland status as the leisure-wildlife balance seems excellent currently, but time will tell.

What's in a spider-skin?

I often write about the identification of small invertebrates, but every now and again I take a slightly more basic approach - maybe a particular structure, or a close look at a more familiar species. So, when I found a moulted spider-skin, it seemed like a good opportunity to look at some general spider anatomy.

Moulted spider-skin, about 6.5mm long from the jaws to the tip of the abdomen (i.e. not including legs or palps). Note how the jaws are dark as they are the most heavily chitinised part. Also, only one pair of legs points backwards.

Zooming in on the jaws, the fangs are clearly seen as overlapping hooked structures - the hole at the end is even visible where venom is injected. Other mouthparts are also visible - the thicker part the fang is attached to is the 'chelicera'. Underneath the base of this (this is a view from beneath) and towards the side, is the 'endite' to which the palp is attached, and between the bases of these is the 'labium'. Behind each fang, protruding forwards of the labium, the 'maxilla' has a 'scopula' of bristles pointing inwards, and right in the middle is the mouth. Essentially, the fangs stab and are moved by the chelicerae, the maxillae manipulate, and the labium provides a surface for them to work against when feeding.

Close-up of a section of leg. As well as the covering of small hairs, there are a few long, dark bristles. The green bars indicate these and their number and arrangement can be important features for the identification of some spiders.

The skin showing that the spider emerged with a split between the eyes (circled) and the base of the chelicerae. The sternum surrounded by leg-bases (coxae) is clearly visible.

The arrangement of eyes in three pairs. The lines indicate the six eyes, showing that the eyes in the outer pairs are closely connected with a shared base, and the central pair are also very close together. This arrangement suggests it is a member of the family Segestriidae (a juvenile male I think), though this is not certain. The two crosses indicate structures that look like eyes but are not (they are artefacts of the photo and were not visible down the microscope - probably just light reflecting off part of the carapace).

As you can see, I've focused mainly on the head as this is where a number of possibly unfamiliar structures are located that are hardened, and therefore remain in shed skins. There are many other structures of interest, but those in the abdomen are lost as it is soft and shrivelled. Also, this is a static specimen - in a live spider, the eyes are actually more-or-less tubular and moved by small muscles - what you actually see here are just the lenses - and of course the mouthparts would be mobile.

If you want to know more about spider identification in Britain, I've given details of a few books below, and there is a 'UK Spider Identification' facebook group, plus of course the British Arachnological Society.

Further reading

Jones, D. (1989). A Guide to Spiders of Britain and Northern Europe. Hamlyn, London.
Jones-Walters, L.M. (1989). Keys to Families of British Spiders (AIDGAP Guide). Field Studies Council, Preston Montford.
Roberts. M.J. (1987). The Spiders of Great Britain and Ireland (3 vols.). Harley, Colchester. [compact 2-volume paperback edition published in 1993, but still £100+ so maybe only for the truly keen!]
Roberts. M.J. (1995). Spiders of Britain and Northern Europe. HarperCollins, London. [plus later editions]

Black beauty - no, not the horse.

I've posted a few times about my stick-insects - Macleay's Spectres (Extatosoma tiaratum) and can report I now have a lot (like, a pint!) of eggs. They were certainly fecund. I'm not currently raising these however, as I have a different species after a friend sent me a batch of eggs of Black Beauty stick-insects (Peruphasma schultei).

Whereas E. tiaratum are fairly common, P. schultei are not, at least not in the wild. They come from northern Peru and are known only from a 5-hectare area at 1200 - 1800 m altitude in the Cordillera del Condor, a mountainous area known as one of the world's biodiversity hotspots. There they feed on pepper-trees (Schinus spp.) but in captivity, are happy with privet, lilac and honeysuckle (and probably some other small shrubby trees too). They prefer drier conditions (40-60% humidity or thereabouts) than species from more humid areas of the tropics and should be fairly straightforward to keep without expensive equipment. They were only discovered and described in 2002 (Conle & Hennemann, 2005) and relatively little is known about them, although tyhey are popular and are cultured and shared around the world without being collected from the wild. 

This means that although there are plenty of care-sheets on the web, they tend to say exactly the same thing based on not-that-much hard evidence - so, amendments and new info is always useful. For example, I have since found out that they are remarkably good at dying. As the hatchlings tend to hide during daylight, they sometimes crawl beneath things, get stuck and starve. So, no more newspaper in the bottom of the hatchery. Some simply failed to thrive, while others were eaten by a larger specimen that turned cannibal despite having plenty of leaves. They are now segregated more carefully and I'm raising a second batch of eggs alongside the original cannibal. Problems aside, they are rather splendid - velvety black except for reddish mouthparts (and when mature, wing-flaps) and yellowish eyes - they are sometimes called golden-eyes stick-insects. Here they are:

New hatchling. Note the white bands near the tips of the antennae.

Side view of about a 3rd instar nymph looking for something to climb onto. The kinked antennae are due to a problem during the most recent moult.

Good view of the reddish mouthparts and yellow eyes.

In 'scorpion' posture. Note the wing-buds.

Reference

Conle, O. V. & Hennemann, F. H. (2005). Studies on neotropical Phasmatodea I: A remarkable new species of Peruphasma Conle & Hennemann, 2002 from Northern Peru (Phasmatodea: Pseudophasmatidae: Pseudophasmatinae). Zootaxa 1068: 59-68.

March of the green vomit-grubs

As you may know, I am a stakeholder in a nearby community farm, here in the sometimes-sunny south of England. We grow many different crops and one of these is a small patch of asparagus. So, I was interested to see some beetle larvae eating the leaves and stems. Fortunately they don't seem to be affecting the asparagus growth noticeably so they've been left where they are (we don't use pesticides but could remove them by hand if they become a problem). Handily, I specialise in chrysomelids (leaf beetles) and recognised them as larvae from this family: the small shiny head capsule, and the body widening towards the rear then coming to a blunt point is typical. I've been looking at writing a guide to juvenile chrysomelids so in this case, knew they were larvae of the asparagus beetle Crioceris asparagi, and the presence of the distinctively colourful adults confirmed it.

Larvae of Crioceris asparagi along an asparagus stem. Adults in the background.

Late instar larva of C. asparagi eating an asparagus stem. This mature larva is close to pupating and shows a typical chrysomelid larval shape (though some differ greatly especially the tortoise beetles in the subfamily Cassidinae).

Larvae such as this are clearly potential prey for insectivorous predators that like juicy grubs. However, while some chrysomelid larvae hide and protect themselves with shields of their own faeces and shed skins, this species has a different approach. When threatened, it arches backwards, raises its head and regurgitates a droplet of partly digested food onto its attacker. This might not do much to a human but could be noxious to a smaller organism, causing the larva to be avoided or giving it time to drop off the plant to safety.

C. asparagi larva with a regugitated droplet on its head.

C. asparagi larva having used its droplet against my threatening finger.

In contrast, a chrysomelid larva (unidentified) with a shield of faeces and shed skins.

Assuming the larvae survive to pupate and emerge from their soil cocoons as adults, their defence changes greatly as they are colourful, warning potential predators that they are (or in the case of this species, are pretending to be) toxic - something known as 'aposematic mimicry'.

C. asparagi adult.

C. asparagi adults creating the next generation.

So, for now I'll enjoy these interesting beetles - hopefully they won't become too numerous...

Nest of tiny delights

Wow - a month since my last post - there has been no shortage of wildlife to write about, just no 'spare' time to do the writing. However, the paid stuff is quiet for a few days at least, so I thought I'd share some observations of the small and hidden, to be precise what I found lurking within a used-and-the-young-fledged robin's nest.

The robin's nest before dismantling.

You never know what'll be hiding in a nest (whether bird or mammal) - there's always the possibility of some under-recorded parasites, plus the array of small invertebrates that simply use the structure as their own. So, a white tray, various tweezers and pins and some time later, this is what I found, along with quite a few Collembola (springtails) and Psocoptera (barklice) which I didn't collect on this occasion as I knew I would have time to work through the identification.

One of three similar pupae a few mm long, currently in my hatchery.

Another pupa, also a few mm long.

A very young spiderling, highly active and I think one of the wolf spiders (Lycosidae)

A tiny dead wasp, probably one of the Pteromalidae, possibly predated by a spider.

The exuvia (skin) of, well, I'm not sure...

Alive and active, the larva of what is probably a 'carpet beetle' (Dermestidae).

So, not much in the way of definite identifications - with juvenile stages, that tends to be difficult, though if any are successfully raised to adulthood, I will as ever update the post. Also, no parasites, but there was good evidence of a thriving community of small invertebrates potentially living out their whole life cycle in the structure of the nest with larvae, pupae, evidence of emergence, predators and prey.

Little soft machine

It's been hot and sunny lately and lots of people have been watching damselflies and dragonflies, including the species that visit garden ponds. One of these is the large red damselfly Pyrrhosoma nymphula and I'd recently seen nymphs, adults and exuviae (empty skins) in and around our pond. However, I hadn't expected to see this when inspecting an exuvium attached to the emergent leaf of a water-soldier plant - a very freshly emerged, pale and soft ('teneral') adult.

Teneral P. nymphula with its exuvium

Teneral P. nymphula showing the pale colour and hardening wings.

 This is a risky time for the damselfly - it is soft, unable to fly and prone to predation. The legs will have hardened first to allow it to grip the plant and leave the evuvium (you can see they are already patterned). Body fluids are then pumped into the wings to expand them from their crumpled wing-bud shape. As you can see, that has happened here and the fluid's colour is the reason for the faint greenish tinge they have. The fluids are them pumped into the abdomen to expand it and give the body its shape. If the wings or body are impeded they may harden in the wrong shape, meaning the damselfly either dies or is unable to fly (and so starves and/or can't find a mate). Even a heavy (relatively speaking) insect can make holes in the wing membrane, as can raindrops. The damselfly's only real defence is to stay hidden - when I got close it quickly flipped behind the leaf to hide itself. As the leaf is spiny and I didn't want it to damage itself, I kept out of the way after these couple of photos were taken.

If all goes well, within an hour, the adult has dried and is likely to disperse once the flight muscles are warm. Sexual maturity may take a few days during which they stay away from aggressive mature males. After this, they join the great mating game!

Portrait of a mature P. nymphula

Long-legged lovers from lakeside leaves

After holidays, after the backlog of work I returned to... it's time for flies - in particular the genus Dolichopus in the family Dolichopodidae (long-legged flies). As well as long legs, most male 'dolis' have very large genitalia, but a post title focusing on that feature might reach the wrong audience... Anyhow, I was watching what I think is D. popularis (there are several similar species in the genus) when I noticed courtship behaviour - so, out came the camera to document a romantic photo-story...

A single Dolichopus

Two males court one female (on the left)

One male is driven off, the other courts the female by standing on long legs over her and rapidly beating his wings.

He tried to mate but was rebuffed (he would dart behind her, but she moved away and turned round), so back to the courting.

This time his efforts were sufficient and the female permits mating.

Female post-mating.

Male post-mating - the large structure bent down from the rear of the abdomen is his genitalia.

Male post-mating.

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!