Thursday, 28 April 2016

Sawflies

Sawflies (Symphyta) are a very understudied group of insects. They belong to the Hymenoptera, which includes Wasps, Bees and Ants, but the female has a saw instead of a sting, hence the common name. The saw is used to cut slots in leaves, and she then lays her eggs into the slots as an anchor to hold them in place, often laying many eggs on a single leaf. The larvae look very much like the caterpillars of moths and butterflies, but they have more prolegs and are generally more tapered, with wider 'shoulders' and narrower rear ends. They also have very simple ocelli on the larger eyes, only a single dot rather than multiple dots as found on moth larvae.

Larva of Arge gracilicornis
The eggs are laid on particular plants, sometimes a single species of plant, but often within a closely-related family of plants. Some species are leaf miners and some others make galls, although the majority of larvae are free-ranging.

I'm not quite sure why Sawflies are so studiously ignored by many entomologists. True, there are many species and many are very similar to each other, often requiring a specimen and a microscope to identify accurately, but other groups are like this, so I'm not quite sure why they are seen as 'difficult'. I suppose it must be a lack of literature: there is very little out there: the main key (Benson in 3 volumes) is now over 60 years old, but I have found the key to be no more difficult than other groups such as beetles or flies. One difficulty is the larvae: they go through a series of moults (instars) as they grow, and can vary their colour pattern quite substantially when they do so. So in order to identify the larvae we need to know all the variations for each species. Cameron's four-volume monograph, written in the late 19th century, includes coloured drawings of some larvae. A further difficulty is that we don't yet have a full knowledge of which larvae turn into which adults. With moths and butterflies, the match is more or less complete, since a great deal of work has been done with them and they are relatively easy to breed through in captivity, but with sawflies the life cycle can sometimes be a bit more complex, and many attempts to raise them in controlled conditions have failed. So we have a situation where some larvae are as yet unidentified, and the larvae of some of the adults are unknown. Clearly, much work needs to be done here.

Adult sawflies can be difficult to distinguish from other groups, but they always have a thick waist like bees, rather than a narrow one like wasps. The thorax is often strongly sculptured.

Tenthredopsis nassata
 
Tenthredo livida, male
Larvae often adopt a tail-up stance when disturbed. The movement is quite sudden, and I have seen parasitoids being propelled through the air if they approach too closely. This is the larva of Nematus pavidus, which is a common Willow feeder:

Larva of Nematus pavidus

The differences between species are often microscopic, and we need to examine a specimen under magnification. With some species we need to see further details, such as the shape of the teeth on the saw. This is the (2 mm,) saw of a Tenthredo:

Saw of a female Tenthredo sp. Sawfly

A few years ago I studied a series of colonies of Nematus pavidus on my local Willow and it is documented here.

Sawflies certainly need attention, and I intend to focus on them this year.

Monday, 18 April 2016

Leaf-miner recording scheme for Ireland

Last week the National Biodiversity Data Centre in Waterford launched a national recording scheme for leaf miners. I have been working on a national checklist for miners for several months and the scheme allows recorders to enter records of leafminers and upload images for verification.

Leaf-miners are a largely ignored group of insects from four groups: micromoths, flies, sawflies and beetles, and hopefully the scheme will raise awareness and produce many records for these groups and perhaps result in some new species for Ireland.

I also produced an introduction to leaf miners which will help people to identify their finds. The introduction and checklist can both be downloaded from here.

Leaf miners are the larvae of insects, and they can be detected by the track they make as they feed inside the leaf. Since they spend all of their larval life inside a leaf, they are very small: some of the adults are only 2-3 mm long.

Mines are identified primarily by knowing the host plant: many miners feed on a single plant or family of plants, so knowing the host plant immediately reduces the number of miners to be considered. Once we know the host plant, then further identification relies on shape of the mine, pattern of the frass (dung) in the mine and perhaps details of the larva or pupa.

Here's a shot I took of the fly miner Phytomyza ranunculi on Lesser Celandine:

Phytomyza ranunculi on Lesser Celandine


There are two main possibilities for this mine, the other being Phytomyza ranunculivora, which has the frass in more discrete lumps:

Phytomyza ranunculivora on Creeping Buttercup


Although Phytomyza ranunculivora hasn't been found in Celandine in UK or Ireland, it does use that plant in other parts of Europe, so it's always wise to check in case we can add a new foodplant for that species. The photograph above shows it on Creeping Buttercup, which is closely related to the Celandine, and was the first (and still only!) Irish record when I found it in 2010.


Friday, 15 January 2016

10 years for an id

Back in December 2005, I encountered a hair-like ice formation on grounded twigs in Steeple wood. I thought it might be related to some kind of fungus, since the twigs were clearly rotted to some extent, but I couldn't get an id. In July 2015, Swiss scientists discovered that the 'Hair Ice' is caused by the crusting fungus Exidiopsis effusa, but only when a precise set of conditions is met.

It seems that water is drawn into the twig, saturating it, and the crust fungus exudes the water through pores. When the temperature, humidity and air are exactly right, the extruded water freezes and forms the hair-like structures we see in these photographs.

'Hair Ice' caused by Exidiopsis effusa 

'Hair Ice' caused by Exidiopsis effusa 

There is one previous record of the fungus from Ireland, made in 1993, but I suppose that must have been the original crust, rather than the 'Hair Ice'. So I have to settle for a second Irish record, with a Donegal first.

10 years for an id isn't too bad I suppose.

Coincidentally, we are experiencing the first cold snap of the winter, with lying snow and sub-zero temperatures. This was the view from my front window this morning as the sun rose behind falling snow:


Wednesday, 14 October 2015

Sunflower (part two)

The Sunflower continues to attract butterflies. This Red Admiral is the third species I have seen nectaring after the Small Tortoiseshell and Peacock last week. A passing Speckled Wood didn't seem so interested. I have seen  this butterfly on the flower for three consecutive days, now.

Red Admiral on the Sunflower
Red Admirals have two generations each year. The first generation is migrant from France (or perhaps even further south) in springtime, and their offspring feed on nettles, emerging from late August to October and then heading south. In recent years, however, adults have been found overwintering in the south of Ireland (and England), So, as warming takes hold, we're seeing a transition from solely migrant to partially resident populations.

Phenology has also changed in some moths. Some species were described by their flying (or emerging) dates. So we have August Thorn, September Thorn, Winter Moth, November Moth, December Moth, etc. But in the couple of hundred years since they were named, weather patterns have changed, and their names are not so accurate nowadays. This August Thorn is a new species for my list, and can be separated from the September Thorn by the kink in the rear band of the forewing (arrowed).

August Thorn moth
This is a locally common moth, feeding on larger broad-leaved trees.

I suppose it's worth pointing out that the season for September Moth often starts earlier than the August Moth! Of course, it isn't just moths that are altering emergence and migration patterns. Birds like the Redstart and Fieldfare that used to arrive as winter visitors have become very scarce nowadays, since they stay in situ and overwinter further north. Flowering plants are also extending their flowering season. Have a look in plant books from a few decades ago, and their 'flowering seasons' will surprise you.

Friday, 2 October 2015

Sun!

Our summer has been one long stream of anticyclones coming in over the Atlantic, bringing high winds and rain for almost four months. As a result, flying insects have been far less frequent than usual, with hedgerows and verges almost deserted for much of the year. Flowering plants don't seem to suffer quite as much, but perhaps the number of blossoms is down.

Late September and early October have seen the arrival of a high-pressure system that has 'stuck' in place over the UK and Ireland, bringing dry days and colder nights. The circulating wind has brought warm southerly air to Ireland, leading to an influx of European species to supplement the meagre numbers of locals. At one point last week I had 7 specimens of Silver Y moth in my greenhouse.

By a strange coincidence, this is the time of year for the second generation some of our native butterflies to emerge and prepare for hibernation. A large Sunflower which I grew this year has been very attractive to Small Tortoiseshell and Peacock butterflies:

Small Tortoiseshell

Peacock
These will hibernate until March or April next year, when they will emerge to lay eggs, and the first 2016 generation will start. Both of these species use Nettles as their sole foodplant.

This is the first year for my new greenhouse and I tried different plants to see how they got on. I noticed after a while that pollination was largely being performed by a single male Episyrphus balteatus hoverfly:

Male Episyrphus balteatus
He was seen most days for perhaps 3 weeks, and made no attempt to escape through open vents or doors. Seems he was content to have a monopoly of the tomatoes, cucumbers, peppers and melons.

Sunday, 16 August 2015

Tattynure bioblitz

A return trip to one of my favourite locations. The land is being very sympathetically 'encouraged' for support of wildlife, and it's showing. The site is yielding either first Irish, first Northern Irish or scarce species in good numbers, and I always expect to find something new.

One particular area is very good for leaf miners. I found the micromoth Stigmella magdalenae, which is the second NI record, and the first since 1995:

Mine of the micromoth Stigmella magdalenae on Rowan

On the same tree I also found Stigmella nyrandriella:
Mine of Stigmella nyrandriella on Rowan

The main difference between these two species is the frass pattern: very narrow in magdalenae and more dispersed in nyrandriella.

Both new to my Species Index.

Some leaves on Bog Myrtle are very small, but I noticed mines on even the smallest leaves. It's Stigmella salicis, which mines Willows and Bog Myrtle:

Mine of Stigmella salicis on Bog Myrtle
I deliberately left my fingers in the shot for scale: the mine is around 15 mm. from left to right, and the adult moth is 4-6 mm. wingspan.

Also new to my  Species Index.

Another stunner is the parasitic fly Tachina grossa. This fly is one of the largest flies in Europe, and is larger than most queen bumblebees. These parasitise larger moth larvae: the host must be large enough to support multiple larvae of this huge insect.

The parasitoid fly Tachina grossa
Also new to my  Species Index.

I'm not quite sure if the epithet 'grossa' refers to its size or its appearance.

As an aside, I'll mention that the fungal season has well and truly started in Northern Ireland. We found several mature fungi in good condition.

Wednesday, 8 July 2015

More from Murlough

Bioblitz at Murlough:

I had set people the task of bringing back any leaf galls that they found, and my workbench was soon loaded down with specimens.

The first specimen brought in was Aceria pseudoplatani made by a gall mite on Sycamore:

Aceria pseudoplatani on Sycamore
The gall is on the underside of the leaf, but is visible from the top as a yellow depression which makes it quite obvious. There is one previous record from Dublin last year. Murlough is also on the east coast, so I suspect it might just be newly colonising from the UK.

This Phanacis hypochoeridis (wasp) gall on Catsear was locally very common: I saw it in a couple of separate locations and almost every plant seemed to be galled. It's described as rare, so it must be very local. First Irish record was submitted last week after I identified the specimen! Each gall is a series of chambers, each one containing a yellow larva.
Phanacis hypochoeridis on Catsear 
New to my Species List
Bombus lapidarius - Red-tailed Bumblebee isn't rare, but I have never seen it on my patch. Here it is gathering pollen on a new flower for me: Restharrow

Bombus lapidarius on Restharrow

Both new to my Species list


This Yellow Shell moth flew over my shoulder and hid under a stile step. So this shot is taken with me lying on my back facing upwards at the underside of the step. Flash used. 
Yellow Shell moth
New to my Species List (which is badly in need of an update now!)

I'm getting lots of reports of the excellent hoverfly Volucella pellucens at the moment:

This was also taken at Murlough:

The hoverfly Volucella pellucens

This Cixiid landed on my recording sheet and I managed to get a couple of shots rattled off before it flew. It isn't the much more common Cixius nervosus, and seems to match Cixius cunicularius very closely.

Cixius cf. cuniculariu

Cixius cf. cunicularius
I can't find any previous records for this local species in Ireland.

I think my personal species tally for Murlogh was around 200, with 2-3 new records for NI and perhaps one new species for Ireland. I'm awaiting confirmation of id's before I report fully.