Can you dig it?

The grasshoppers (Orthoptera) is a large order of insects and a familiar one. The Orthoptera contains two sub-orders, the Ensifera (crickets and katydids) and the Caelifera (grasshoppers and locusts). These suborders can be distinguished by the length of the antennae, mechanisms of sound production and the ovipositor shape in females. Within the Ensifera are the Grllotalpidae, also known as mole crickets. These fascinating insects are the subject of this blog.

Mole crickets are large insects, being 4-5cm long and 2-5g in weight, and are dark brown with velvety hairs. Their subterranean lifestyle is betrayed by their spade-like forelegs, modified for digging. Adults can fly, with the exception of the short-winged mole cricket Scapteriscus abbreviatus, though the wings of males and females are different.

Mole crickets have a hemimetabolous lifestyle - incomplete metamorphosis with no pupal stage. As an example, female Gryllotalpa gryllotalpa lay 100-300 eggs in a chamber curing the summer. They exhibit maternal care as the nymphs move through 6-8 stages, with it taking more than a year for them to complete development. The adults are nocturnal and hibernate over the winter.

The burrow system of mole crickets in complex. The network has a horn entrance (A), where the male can also amplify his 'voice' as he sings. There is the nest chamber (5), grazing areas linked by horizontal tunnels 6), hideaways at the end of vertical tunnels (7) and at least another horn entrance, which can act as an escape route (B).

The Gryllotalpidae are distributed across the USA, South America, Europe, North Africa, Asia and New Zealand. The European mole cricket Gryllotalpa gryllotalpa comprises 13 sibling species/chromosaomal races through Europe and North Africa.

Whilst native species are not generally seen large-scale pests (though they formally were in the UK), some introduced species are serious pests, mainly in the south eastern USA.

• Gryllotalpa gryllotalpa - European mole cricket (not a major pest)
• Scapteriscus abbreviatus - short-winged mole cricket
• Scapteriscus borellii - southern mole cricket
• Scapteriscus vicinus - tawny mole cricket (major pest)  

Mole crickets are seen as pests because of the damage they cause through their tunnelling behaviour, whilst tawny and short-winged mole crickets also feed on crops. Control of pest species uses soil applied insecticides and a range of biological controls - nematodes, fungal pathogens, Tachinid flies, Sphecid wasps and Bombardier beetles (which feed on the eggs).

In the UK, the European mole cricket Gryllotalpa gryllotalpa is a conservation priority. They are on the Red List, and protected under Schedule 5 of the Wildlife & Countryside Act 1981. Their population declined due to habitat degradation, with the last native sighting in Wareham, Dorset in 1981. Species recovery programmes were run by English Nature, though these were not successful and have now finished.

In 2014 a small population was found in the New Forest , Hampshire. This is suspected to be from imported insects, though it is not clear which species is involved and taxonomic study is needed to establish the species and the origin. 

Potential future conservation action would involve a captive breeding programme, from suitable foreign populations, with a relaease programme and raising public awareness.

The ice crawlers

I have recently been learning about the Grylloblattodea, one of the smallest and the most threatened insect orders on earth. These fascinating insects are given the fantastic colloquial names of ice or rock  crawlers, and are found in cold mountainous areas of the Western USA and Asia.

In looking into the species in more detail, I found an excellent blog by Piotr Naskrecki, which is highly recommended reading here.

Grylloblatta campodeiformis - Piotr Nascrecki

Grylloblattodea get their name from the combination of features similar to Orthopteran (Grylloid) insects - external sword shaped ovipositor in the female, tentorium 'skull' structure - and Blattodean (cockroach) insects - five-segmented tarsi, multiarticulate cerci, assymetric male genitalia. There are number of features that can be used to distinguish the Grylloblattodea:

• long and slender antennae
• reduced (or absent) compound eyes, with no ocelli (simple eyes) present
• apterousness (being wingless)
• metathoracic spine (unique in the hexapods)
• eversible sac on first abdominal sternum
• long and slender legs, adapted for walking
• long, multiarticulate cerci (at the rear of the animal)
• long, sword-shaped female ovipositor (almost as long as cerci)
• assymetric male genitalia
• simple, chewing, foreward-facing mouthparts

Typical habitat in Western USA - Piotr Naskrecki

These are hemimetablous insects, meaing that they have an incomplete metamorphosis and their life cycle is a quite simple one of egg to nymph to adult. They are long-lived, with a lifespan of around five years, though this is thought to range to up to ten years. As typical of long-lived insects, the nymphal stage takes two years to mature.

The Grylloblattodea are cryophilic, meaning that they are adpated to cold environments. Their optimal temperature range is just 1-4 degrees C, though they can tolerate between -8 and 10 degrees C (and species in Asia can apparently tolerate even higher temperatures of 9-15 degrees C).

They are found at high elevations on glaciers, where they are mainly nocturnal, or at lower elevations in caves with permanent ice. Given the extreme environments in which they are found, their diet is quite broad, they probably cannot be too choosy. Species can be omnivorous scavengers of dead insects as well as plants, fungi and detritus.

The order Grylloblattodea contains one family - the Grylloblattidae. This contains  around 26 species (probably more) in five genera.

• Grylloblatta - 11 species found in the USA
• Grylloblattella - 2 species, found in China
• Grylloblattina - 1 species, found in Siberia
• Namkungia - 1 species, found in Korea
• Galloisiana - 12 species, found in Japan and China

Galloisiana nipponensis, a blind species from Japan - Piotr Naskrecki

The populations of species in Grylloblatta have been reaersched in the Western USA. They are found in the Cascade mountain range, streching from British Columbia to Oregon, and the Sierra Nevada in California. In these areas they have been found in high altitude ice caes (300m-1000m) and north-facing talus and glacial margins (1500-3000m). Migration is limited, and they certainly cannot move at lower elevations, mneaning that populations are isolated.

Because of their limited ability to move, narrow environmental niche and small distribution, the insects are very vulnerable. The impacts of habitat loss and global warming are seen as strong threats to many species. SPecies in the order are placed in the IUCN red list in the near threatened, vulnerable, endangered and critically threatened categories.

Whilst the Grylloblattodea have successfully occupied particular niches through becoming specialists, habitat changes ate global warming pose a significant threat. This is an example of how specilaist species can be more extinction-prone that generalists. 

Scaffold

We have builders in again, but this provided a bit of an impromptu opportunity for moth recording yesterday. On my afternoon coffee break I noticed a plume moth high on the side of the house, but within reach of the scaffolding. So I clambered up, feeling a little shaky with my morbid fear of any height that inolves my feet leaving the ground, and managed to pot it.

New moth observation platform

The moth proved to be a Beautiful Plume Amblyptillia acanthadactyla, only the scond I have recorded here in Batch Valley. Remarkably, this small moth hibernates and reappears in the late spring. It was very atcive, so I had to settle for this in-the-pot photograph.

Beautiful Plume Amblyptillia acanthadactyla

I took a stroll around the garden to recover from the excitement, and was delighted to find this Grey Dagger Acronicta psi larva in a hawthorn (Crataegus). I regularly catch Dagger moths in the summer, but it is impossible to identify whether these are Grey or Dark Dagger A. tridens without resorting to dissection. Fortunately, the caterpillars are completely distinctive. This is the second Grey Dagger larva I have found in the garden, so I am still not sure whether Dark Dagger occurs.

Grey Dagger larva Acronticta psi

A Hitchhikers Guide

On Wednesday I arrived home from a long day working in Birmingham to a plastic box by the back door. Being known as the village entomologist (or possibly the village weirdo) means I get given a wide variety of interesting invertebrates by neighbours (and sometimes inanimate objects that resemble something living), so this in itself was not a surprise.

Jo also collects anything interesting she sees in the garden, and I soon discovered this was in fact a welcome home present from her. She had found a beetle in an old plant pot whilst gardening and thought that I would want to see it. The beetle in question was this Dor Beetle Geotrupes stercorarius. 

Dor Beetle Geotrupes stercorarius

This species looks almost identical to the Common Dumble Dor G. spiniger, although Dor Beetles tend to have more distinct ridges on the wing cases. To check the identification you really need to look at the ventral surface of the abdominal tergites, or in laymans terms you turn it on its back and look at its bottom. G. stercorarius has hairs and punctures across the width of the tergites, as can be seen in the picture below, whilst these are much less extensive in G. spiniger.

Dor Beetle Geotrupes stercorarius with a species of phoretic mite

Dor Beetles are alternatively known as dung beetles. They will dig a tunnel under a suitable piece of dung and line this tunnel with the dung for the larvae to feed on. The horse field opposite my house is a potential breeding ground for Dor Beetles, though the horse dung tends to be collected up religiously every morning to rot down into horse manure! Apparently Dor Beetles have also been recorded using decaying fungi and rotting plants in woodland habitats in a similar manner.

The other noticeable feature of Dor Beetles, as the pictures show, is that they are often infested with mites. This individual was no exception, and was living up to one the best colloquial names of all insects, the Lousy Watchman. It would be easy to assume that these mites are parasites that cause the beetle harm, perhaps they are eating it alive? In fact the truth is far more interesting and remarkable.

These are a species of phoretic mite, and so belong to the same class as ticks, spiders and harvestmen - in other words they are Arachnids. Phoretic mites use the strategy of hitching a lift on the bodies of beetles and bumblebees to travel between food sources. They do not harm their host, this would not be a sensible evolutionary strategy, unless perhaps they are so numerous that they weight it down. This seemed to only be a mild infestation, so are probably not causing this beetle too much of an inconvenience.

Dor Beetle Geotrupes stercorarius with a species of phoretic mite

These mites belong to the Acari taxon, a large group comprising mites and ticks. The Acari are comparatively little studied. In fact, according to the Natural History Museum, there are at least 54,000 species worldwide, with many hundreds surely yet to be classified. They have roles in agroecosystems and potential uses as archaeological indicators of change. There are no easily available resources for identification, but NHM are currently producing these, which will surely make this group more accessible.

Given this, getting an identification for the Dor Beetle's travelling companions is a bit of a challenge. However, after a bit of research these mites appear likely to be Peocilochirus carabi. A check on the NBN gateway shows just how under recorded this group is. For this species, which is surely widespread and common, there are only records from two adjacent 10km squares in East Anglia, and no others at all in the UK. This makes these mites a potential VC40 first. I have contacted those working on the NHM project to see if they can confirm identification, and will provide an update if they can help.

This goes to show that sometimes a closer look at one insect, can reveal something else unexpected, but often quite fascinating.

Autumn colours

Moths often seem to match the seasons. Moths in the summer can be colourful and bold, those flying in the winter are typically dingy grey and those in autumn are often muted shades of orange, brown, yellow and green. It was much an orange and brown feel in the moth trap this morning. Again the Lunar Underwings Omphaloscelis lunosa dominated, but there were a few other subtle surprises.

Lunar Underwing Omphaloscelis lunata

This Beaded Chestnut Agrochola lychnidis is the first record for my Batch Valley garden. It is apparently particularly attracted to mercury vapour light traps, and as my first autumn with an MV perhaps I can expect this be become a regular autumnal feature.

Beaded Chestnut Agrochola lychnidis

The closely related Brown-spot Pinion Agrochola litura was also present. I catch small numbers of this lovely moth each autumn and it is typically found in woodland, scrubland and mature gardens.

Brown-spot Pinion Agrochola litura

I also had a coople of interesting insects in the by-catch. There was this attractive Mirid bug Pantilius tunicatus, which is a late season species found on the lower branches of a variety of trees. A shame that my camera refused to focus on it!

Pantilius tunicatus

There was also this small Empididae fly, which I have been seeing around the garden. It is one of the Rhamphomyia species but the specimen will need detailed examination to get to species level.

Rhamphomyia species

On the rampage

A regular sight resting on the walls of the house at the moment are these craneflies, with distinctively patterned wings held closed over the body. There are a few species flying at this time of year, but this species is Tipula confusa.

Tipula confusa

This is a late flying species, typically found from September to November. The larvae live in moss across a variety of habitats, which I suspect are not in short supply around the Shropshire Hills. There has been a lot of talk in the press in recent weeks about 'rampaging' craneflies. Not sure that I am too worried.

Pick'n'mix

One of the typical autumn moths is the Lunar Underwing Omphaloscelis lunosa. For a few weeks in September and October this species will dominate the moth trap, sometimes being the only species.

A trap for the unwary or inexperienced, this moth comes in a wide variety of flavours, with colours ranging from yellowish-orange to dark brown, as this mornings catch demonstrates.

Lunar Underwings Omphaloscelis lunosa

This species is one of those that overwinters as a larvae, feeding on various grasses. This may be somewhat surprising, given the late appearance of this species in the year.