A Mayfly in December

Mayfly

It has been a a mild winter here in Ireland, especially considering the arctic conditions of two and three years ago. It is therefore not unusual to see a few strange phenological events occurring, such as plants in full flower and moths on the wing. One of the oddest, yet most delightful that I have seen recently is most certainly an adult mayfly, on the wing, not eleven days ago some 17 km from Cork city. It was odd because, as the name suggests, mayflies tend to emerge around May. Yet the emergence period for some species can from March to October. Still, seeing one a little over a week from Christmas was a little peculiar.

This sighting is also of interest as it brings to mind the recently published Red List of Irish Ephemoptera (1), detailing a check-list of the Irish species and their conservation status. Ireland is home to 33 species of mayfly, quite a low number in comparison to that of mainland Europe (350 species, (2)). However, even this relatively low number of species contributes greatly to their associated aquatic habitats. Mayflies spend the majority of their life in nymphal form (in some cases up to three years), and the feeding of these nymphs contributes greatly to the cycling and availability of nutrients in aquatic habitats (3). Such feeding can also greatly contribute to the cleansing of water systems and help maintain their integrity. On emergence from the nymphal stage the mayfly, uniquely in the insect world, passes through two terrestrail adult stages: the winged subimago and the winged and sexually mature imago. The life of these two stages is quite short in comparison to the nymphs (little more than a couple of hours in some stages), but large scale, synchronous emergence of adults results in significant movement of nitrogen and phosphorus from aquatic to terrestrial environments (3).

Check-list of Irish Mayflies. Key: CR = Critically Endangered, EN = Endangered, VU = Vulnerable, NT = Near Threatened, lc = least concern dd = deficient data.

Species	Conservation Status
Siphlonurus armatus	CR
Baetis atrebatinus	EN
Ephemerella notata	EN
Rhithrogena germanica	VU
Procloeon bifidum	VU
Leptophlebia marginata	VU
Kageronia fuscogrisea	NT
Ameletus inopinatus	NT
Baetis fuscatus	dd
Alainites (Baetis) muticus	lc
Baetis rhodani	lc
Baetis scambus	lc
Baetis vernus	lc
Caenis horaria	lc
Caenis luctuosa	lc
Caenis macrura	lc
Caenis rivulorum	lc
Centroptilum luteolum	lc
Cloeon dipterum	lc
Cloeon simile	lc
Ecdyonurus dispar	lc
Ecdyonurus insignis	lc
Ecdyonurus torrentis	lc
Ecdyonurus venosus	lc
Electrogena lateralis	lc
Ephemera danica	lc
Heptagenia sulphurea	lc
Leptophlebia vespertina	lc
Paraleptophlebia cincta	lc
Rhithrogena semicolorata	lc
Serratella ignita	lc
Siphlonurus alternatus	lc
Siphlonurus lacustris	lc

In Ireland, six species of mayfly are listed as critically endangered, with two more near threatened (1). All of these species have restricted distributions and it is unfortunately unsurprising that they are classed as such. The are species found in streams and rivers, which points to the increased pressures of pollution that these habitats have had, and unfortunately continue to have (1).

References:

1. Kelly-Quinn and Regan, 2012. Ireland Red List No. 7: Mayflies (Ephemeroptera). National Parks and Wildlife Service, Department of Arts, Heritage and the Gaeltacht, Dublin, Ireland
2. Brittain, Michel Sartori, 2009. Encyclopedia of Insects pp. 328-334
3. Burian, 2009. Encyclopedia of Inland Waters pp. 299-314

A Winter-time Orange

Yellow Brain Fungus, Tremella mesenterica

Trees denuned of their leaves can make for many a forlorn vista at this time of the year, but they do provide the opportunity to spot some strange fruit indeed. Arboreal fungi that would otherwise remain obscured are quite visible among the bare branches. One of the most obvious is the shocking-orange coloured Yellow Brain Fungus (Tremella mesenterica). For all the world looking like somebodies discarded worryingly luminous bubblegum, T. mesenterica is (like all members of the Tremella genus) an obligate parasite of other fungi. In Ireland it is most commonly encountered on Gorse (Ulex spp.), where its host is most commonly found growing, fungi of the genus Peniophora. Indeed, T. mesenterica is often found growing on the upper part of a Gorse branch with the Peniophora species producing fruiting bodies on the underneath of the branch (1).

Yellow Brain Fungus, Tremella mesenterica

T. mensenterica's almost cartoonish colour belies an organism that has shown itself to have a number of surprising and useful applications. For example, fruiting bodies of the fungus fed to rats with diabetes have been shown to have a significant effect on the disorder (2). It also posses extracellular polysaccharides that have been shown to have immunomodulatory properties and thus may have potential in anti-tumor and anti-inflammatory treatments (3). Specifically, it has been shown to surpress the production of hormones (human chorionic gonadotropin) associated with tumor cells and therefore may have a role in the chemotherapeutic treatment of certain forms of cancer in the future (4).

References:

1. Roberts, 1995. Mycologist 9 pp. 110-114
2. Hui-Chen et al., 2006. Life Sciences 78 pp. 1957-1966
3. Nan-Yin et al., 2006. Food Chemistry 99 pp. 92-97
4. Yen-Wen et al., 2006. Life Sciences 79 pp. 584-590

The Holly and the Ivy... and the Ivy

The two leaf forms of ivy (Hedera helix), cordate (left) and palmate (right)

Its Christmas time, and all around the house... people have placed a variety of plants to add to create a festive spirit about. Poinsettias have become quite popular in this part of the world (and make a convenient, low risk present for neighbours), but the traditional Christmas trees and garlands of holly and ivy are still the most popular. All three of these now Christian traditions arose from older traditions (1): ivy (Hedera helix) in particular was considered a sybol of female fertility because of its late flowering period (September to November) and production of berries (around this time of the year) (2). Although it can be quite an invasive pest in some parts of the world, these two facts make it an important source of nectar and pollen for insects in late autumn/early winter and an equally important source of food for birds later in the year in its native range.

However, one of the most striking features of holly is that two distinct, different leaf shapes will be seen on the one plant - a five lobed, palmate form and a cordate form that shows little to no lobing. The lobed leaf is found on the climbing, juvenile stems of the plant, with the cordate form on the flowering stems. This is known as heteroblasty, a phenomenon that is found in many plant species, but that is most famously illustrated in ivy. It was first described by Karl Goebel in 1898, who noted that as plants grow they add new modules (stem with attached leaf) which show gradual changes of form in most cases (3). However in some species, such as ivy, the changes are more dramatic. The reasons for this are still unclear but defence against herbivory and nutrient and water supply differences have been suggested as causes (3). Indeed, Ivy has been shown to produce palmate leaves in low light conditions and cordate leaves in high light (4).
 

References:

1. Miles, 2008. Christmas in Ritual and Tradition, Christian and Pagan p. 275
2. Phillips, 1977. Wild Flowers of Britain p. 172
3. Zotz et al., 2011. Botannical Reviews 77 pp. 109–151
4. Rogler and Hackett, 1975. Physiologia Plantarum 34 pp. 141–147

Hiding Out With The Cuttlefish

Common Cuttlefish (Sepia officinalis)

The ability of cephalopods to vary their colour has been known since antiquity and while most species can achieve impressive colour changes, few can match the common cuttlefish (Sepia officinalis) for sheer dramatic quality. This is in part due to the size (1.5 mm in diameter) and density (50 per square mm) of the chromatophores (1), the neurally controlled colour bearing organs that can change the pigmentation and hence appearance of the animal with incredible detail. However in part it is, as the chromatophores are just one movement in the symphony that makes each animals body pattern.

Body pattern change is used in feeding feeding, avoiding predators and communication, and is therefore an integral part of S. officinalis life history. Its most striking aspect are the chromatophores, organs that are unique in the animal kingdom to cephalopods. Body pattern is controlled in a hierarchical fashion in S. officinalis: behaviour will dictate body pattern and hence organ response. Body pattern is constructed using four components, such as coloration of which chromatophores play a part. However, they are aided by organs such as leucophores which scatter light of all waveslengths and iridiphores, which produce interference colours when viewed from certain angles, often giving pink and iridescent greens and blues (1). The other three components are textural (the smoothness or papillation of the skin), postural (the orientation of the body parts) and locomotor (the action of the animal, e.g. resting, burying, scuttling, etc.). These components are themselves divided into units which are in turn divided into elements, such as the previously mentioned chromatophores. This complex hierarchy of organisation allows for the wide variety of body shapes observed in S. officinalis.
 

Such an intricate response mechanism is under tight control of the central nervous system and is driven by visual stimuli. Environmental cues taken in by the eye and transferred to the optic lobe where information is processed and transferred to the lateral basal lobe which will control motor response (1). Amazingly, these neural areas are already well developed upon hatching in S. officinalis and newly emerged cuttlefish are immediately able to conceal themselves from predators (2). They use strategies such as colour resemblence, disruptive coloration, obliterative shading, shadow elimination, disguise and adaptive behaviour to avoid becoming a meal from fish such as the Comber (Serranus cabrilla).
 

Human ability to distinguish symmetrical objects easily and quickly lead to the assumption that the use of these behaviours would be greatly enhanced by the use of asymmetrical patterns. However, it has been demonstrated that in cryptic behaviour, S. officinalis will exhibit a high degree of bilateral symmetry (3). This seems counter-intuitive: symmetrical objects would stick out much more obviously in a random, asymmetrical environment. Yet S. officinalis is notoriously difficult to spot in its native environment. This may be due to a number of factors (3). Predators of S. officinalis may not use symmetry as a visual clue. Also the orientation of the axis of symmetry is important, as unless the axis is horizontal or vertical, symmetry becomes less apparent to the viewer. Alternatively, symmetry may play a vital role in concealment. By highlighting a symmetrical pattern on its body, S. officinalis may be taking the emphasis off its own body shape, making it seem just an interesting but inedible artifact to its predators.

References:

1. Hanlon and Messenger, 1998. Cephalod Behaviour pp. 31-46
2. Langridge, 2006. Proceedings of the Royal Society Series B 273 pp. 959-967
3. Hanlon and J. B. Messenger, 1988. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 320 pp. 437-487

Cuttlefish picture taken at Galway Atlantiquaria, Salthill, Co. Galway.

First Irish Record for the Southern Oak Bush Cricket

Ireland is home to 12 species of breeding orthopterans (grasshoppers and crickets), with five of these being classed as crickets or bush crickets (1). It is only in the last thirty five years that three of these have been recorded, with Pholidoptera griseoaptera, the Dark Bush Cricket, being first recorded as 1983 (2). This trend may be due to the lack of attention that Irish orthopterans have been paid in the past, or may be a phenomenon that has been seen in European dragonflies, that of the spread of certain species from the center of mainland Europe to its peripheries.

Female Southern Oak Bush Cricket, Meconema meridionale

This is most evident in the case of the Southern Oak Bush Cricket, Meconema meridionale. This species was thought to be an exclusively Southern European species, but has extended its range and during the 1990's was to be found in France, Holland and Belgium (3). In 2001 it had reached Britain (4), being discovered in three localities in England from where it has steadily spread. This introduction was though to have been via imported horticultural material and given the strong trade links between Britain and Ireland it is assumed it can only be a short time before M. meridionale reaches Irish shores. And so it has proved to be. On the 9th of November last, I spotted a female adult M. meridionale on a limestone pillar at the entrance to a building on the Western Road in Cork city. The weather at that point had been unseasonably warm and when I first saw it I assumed it was the closely related (and Irish native) the Oak Bush Cricket (Meconema thallasinium), a species often seen close to houses and other buildings. However this individual was lacking in the distinctive long, green wings associated with M. thallasinium and was in fact brachypterous (having abnormally small wings). This is the distinguishing feature of the otherwise almost identical M. meridionale. This may be an errant traveling individual, but the species recent range expansion points to the discovery of a breeding population in Ireland being a very distinct possibility in the not too distant future.

References:

1. Haes and Harding, 1997. Atlas of grasshoppers, crickets and allied insects in Britain and Ireland
2. O'Connor and O'Connor, 1985. Entomologists' Gazette 36 pp. 229-232
   Maclean, 2010. Silent Summer: The State of Wildlife in Britain and Ireland p. 533
   Hawkins, 2001. British Journal of Entomology and Natural History 14 pp. 207-213

Hold On

Common Limpet, Patella vulgata

Probably the most familiar intertidal organism on western European coastlines is the Common Limpet, Patella vulgata. Its conical shell can often be seen in enormous numbers on rocky shore of all degrees of wave action, and numbers are maintained by the relatively long life of certain individuals. Where conditions promote slow growth, some individuals can live up to 17 years of age (1). For a sedate looking animal, often encountered encrusted with algae and barnacles, they are voracious feeders. Although they have been reported to consume a wide variety of micororganisms (2), algae of the intertidal zone is the food of choice. And what a choice; P. vulagata feeds a plethora of different species, including Fucus spp., Ulva spp. and red encrusting algae (1). This is all facilitated by the iron and silica hardened teeth on the radula, which rasp the algae with incredible efficiency. In situations where P. vulagata have been artificially removed form shorelines, Ulva spp. have quickly covered the rocks.

Common Limpet Home Scar

A rocky shore is not for the faint of heart, with waves action dislodging anything not firmly attaced to its surface. Organisms need to be firmly attached to the rock, and P. vulgata is truly a master at this. Depending on where the animal is to be found on the rock face, the shell height will vary. Those at high shore levels have tall shells with a small shell length, while individuals at a low shore levels have shorter but longer shells, which keeps them closer to the rock (1). P. vulgata attaches to their substrate by using a combination of suction and glue like adhesion (3). The specific mode of attachment is dependant on their location at the time. At high tide, when P. vulgata is at its most active feeding, suction is employed. This involves decreasing the pressure under the foot of the animal which forms a tight seal with the substrate. At low tide, when foraging does not occur due to the increase risk of predation, P. vulgata employs a glue-like secretion from its foot which creates a seal that is stronger than that created by suction, however it is more permanent and does not allow movement for foraging. At rest, P. vulgata also employs a home scar, a depression created in the substrate by chemical action and abrasion by the shell of the animal. This is returned to after each foraging excursion as it increases the adhesion power significantly (4).

References:

1. Fish and Fish, 2011. A Student's Guide to the Seashore pp. 205-206
2. Jenkins and Hartnol, 2001. Journal of Experimental Marine Biology and Ecology 30 pp. 123-139
3. Smith, 1992. Journal of Experimental Marine Biology and Ecology 1600 pp. 205-220
4. Smith, 1991. Journal of Experimental Biology 161 pp. 151-169

Punk Moth

Pale Tussock Moth Larva, Calliteara pudibunda

With its bleached-blonde mohawk, running halfway down its yellow and black body and a shocking-red spike of tail hair, the larvae of the Pale Tussock Moth (Calliteara pudibunda) is nothing if not an attentions seeker. Yet its wildly flamboyant appearance serves an important role for the caterpillar. Its long body hairs will cause irritation upon handling, and in some cases can cause severe damage to human skin (1). It is therefore avoided by most predators, a fate that the less hirsute adults are unfortunate to avoid, being food for a variety of birds. It is found throughout Europe, and is most common in the south and west of Ireland (2).

Pale Tussock Moth Larva, Calliteara pudibunda

C. pudibunda is a polyhpagous insect, feeding on a range of plants including including hops, birch, elm, flowering cherry, hazel, hornbeam, oak, poplar, pussy willow and walnut (3). Beech is a particular favourite and large numbers have been known to occur that put immense stress on commercial beech plantations. Commercial, monocultural forests such as these are remarkable only for their lack of invertebrate biodiversity due to their lack of floral diversity (4), so lack of competition is partly responsible for such outbreaks. However, the introduction of only a small number of other tree species has been shown to reduce the numbers of C. pudibunda significantly (5). Chemical volatiles emitted from Norway Spruce grown in co-culture with beech will mask the signals that attract egg laying females to the host beech trees. Such inhibition has lead to a 25% reduction in numbers of C. pudibunda in commercial forests.

References:

1. Backshall, 2007. Venom: Poisonous Animals in the Natural World p 49
2. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 112
3. Alford, 2012. Pests of Ornamental Trees, Shrubs and Flowers p. 320
4. Christensen and Jens Emborg, 1996. Forest Ecology and Management 85 pp. 47-51
5. Heiermann and Schütz, 2008. Forest Ecology and Management 255 p. 1161-1166

Blog Awards Ireland Finals

From left to right: Sally from Register 365, John from 21stcenturynaturalist (me), Nicola from The Sequin Cinderella and Steve from Register 365.

 A great night was had by all at the finals of the Blog Awards Ireland on Saturday the 13th last in the Osprey Hotel in Naas. Unfortunately 21stcenturynaturalist didn't take home any prizes, but the Science/Education awards went to the truly excellent Science Calling!, a most deserved winner. Congratulations to Maria Delaney on a blog that always excites and educates me.

Foreground, from left to right:  Nicola from The Sequin Cinderella, John from 21stcenturynaturalist (me), and Steve from Register 365.

Best Blog was awarded to Wise Words, while Best Blog Post (presented by the wonderful people at Register 365) went to Head Rambles for "A friendship of a lifetime". A full list of winners is available here.

Oxtongue in the City

Bristly Oxtongue, Picris echioides

Urban, and for that matter suburban, landscapes are often thought of as ever changing, ever moving. The commonly held opinion is that building works, cleaning and development in such areas make dynamic habitats that only the most adaptable and durable organisms can make anything close to a permanent home in. Rural habitats, which seem to experience less human interference other than agriculture, should be far more suitable for a larger range of organisms. And generally these two statements can be held to be broadly true. However, as always, there are a few delightful anomalies.

Bristly Oxtongue, Picris echioides

Bristly Oxtongue (Picris echioides) is a large and often quite branched annual or biennial of dry, disturbed ground (1). A common plant in southern England and Wales (2), it is of rare and local occurence in Ireland, being found only with any frequency in the South and South-East (1), and is considered to be nationally rare (3). Such low frequency may be explained by its status as an introduced species, being a native of the Mediterranean (4). P. echioides certainly earns its common name, Bristly Oxtongue as it is is covered in bristles arising from small white blisters all over the plant. In the past the leaves were boiled and eaten (2), possible for medical reasons as there is anecdotal evidence that it has an effect on stomach complaints (5). There may be some truth in this, as the aerial parts of the plant contains sesquiterpene lactones, some of which are seemingly unique to P. echioides (6). Its flowers, which from a distance resemble a number of other yellow Asteracea, reveal upon inspection the most wonderfully delicate sepals.

Bristly Oxtongue, Picris echioides

As it is such a scarce plant, it was with great surprise that I received most welcome correspondnace from one Mr. Pat Dunne of Cork city outlining not one, but two locations for this flower in the city. The first is on the docks of the river Lee, near to the city center. At once this area was a very busy access point for the various industries within the city, but with their disappearance or relocation the docks have become less used and this undisturbed habitat has seemingly proved ideal for P. echioides. Similarly, the second site (located in the city suburb of Ballyphehane) is a small section of waste ground in a now disused factory. While this site was in the past tended when the factory was operational, this no longer seems to be the case, which is, again, a boon for the plant. So while cities as a whole may be never ceasing monuments to progress, there are parts of them that remain refreshingly static and a refuge for wonderful organisms.

References:

1. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 252
2. Philips, 1977. Wild Flowers of Britain p. 94
3. O'Mahony, 2009. Wild Flowers of Cork City and County p. 73
4. Preston et al., 2002. New Atlas of the British and Irish Flora p. 928
5. Hooper, 1817. A New Medical Dictionary p. 629
6. Marco et al., 1992. Phytochemistry 31 pp. 2163-2164

A Sighting of the Kidney Spotted Ladybird from Cork

Kidney Spotted Ladybird, Chilocorus renipustulatus

Ireland is home to 18 species of ladybirds, 15 of which are considered resident here (1). All of these species are also present in Britain along with 8 more (2), so it is therefore feasible to think that some of these 'extra' species may appear from time to time in Ireland as migrants. Nonetheless, I was still quite surprised to see an individual Kidney Spotted Ladybird (Chilocorus renipustulatus) on branch of some low growing willow in an unused quarry about 18 km from Cork city center on the 19th of September last. C. renipustulatus is not recorded as being present in Ireland, even though it is of common occurence in England (though less so in Wales and very rare in Scotland). 

Kidney Spotted Ladybird, Chilocorus renipustulatus

The ladybird possessed the characteristic domed elytra which were rimmed at their edges and demonstrated defensive behaviour typical of C. renipustulatus, namely clamping tightly against the surface of the branch it had been moving along. The site at which the ladybird was spotted is quite close to a large ferry port, which may account for its presence there. It may also, however, be a symptom of global warming that has lead to an increase in the numbers of species of dragonfly found in Ireland.

Kidney Spotted Ladybird, Chilocorus renipustulatus

References:

1. http://www.habitas.org.uk/ladybirds/
2. http://www.ladybird-survey.org/default.aspx

A Flying Swimmer

Rhantus sp. Predatory Diving Beetle

A wet, wet, wet summer has given way to a pleasingly dry Autumn here in Ireland, with some of the southern counties experiencing their driest September in 26 years. This has lead to some water bodies which remained swollen throughout the year to finally experience something of a drought. Some of the more temporary examples have began to dry up and with this disappearing of certain bodies, so the predatory diving beetles, the Dytiscidae, take to the wing in search of new hunting grounds. Voracious hunters, they are found in a variety of fresh water habitats such as streams, ditches, canals and lakes, although usually in shallow water (1). Their prey are quite varied, consisting of a wide number of invertebrate larvae as well as tadpoles and worm species (2), and are excellent swimmers with large back legs perfectly adapted to pursue these prey in the water. These are lined with hairs that spread out when the leg is drawn back (in a rowing motion) and then lie flat when the leg is pushed forward, reducing drag (3). Drag is further reduced by the shape of the of the beetle's body which is streamlined for rapid movement through the water. This is tempered somewhat with the need for stability, giving Dytiscids excellent maneuverability.

Rhantus sp. Predatory Beetle

Its something of a shock therefore to see these masters of the waterways barreling through the air with all the grace of a carelessly tossed stone. Moving to new territories, Dytiscids fly with a refreshing directness, generally only halted by the water they come seeking (the individual pictured just managed to avoid me on its approach flight). The fact that many species are of considerable size (up to 4 cm long) makes seeing them a little alarming. This propensity towards large size is linked to reduction of drag in the water, with larger bodies animals experiencing much less drag than their smaller relatives (3). Ireland is home to quite a number of Dytiscidae, with 86 species being recorded here (4).

References:

1. McGavin, 2005. Insects and Spiders of Britain and Europe pp. 86-87
2. Aditya and Saha, 2006. Limnologica - Ecology and Management of Inland Waters 36 pp. 251-257
3. Nachtigall, 2009. In Encyclopedia of Insects pp. 972-975
4. Ferriss et al., 2009. Irish Biodiversity: a taxonomic inventory of fauna p. 98

Finalist in the Blog Awards Ireland

The finalists for the Science & Education section of the Blog Awards Ireland have been announced: and 21stcenturynaturalist has been named as one of the top 6! Again, thank you all for your support, I couldn't have done it without you. Results are to be announced at a gala event on the 13th of October at the Osprey in Naas, Co. Kildare so fingers crossed!

Yellow Bartsia Makes an Appearance

Yellow Bartsia, Parentucellia viscosa

In the past, the hemiparasitic Yellow Bartsia (Parentucellia viscosa) was a very common member of the flora of damp pastures through out south west Ireland (1). Unfortunately the prectice of draining such paludal habitats throughout the 20th century led to a dramatic reduction in its numbers in the Cork and Kerry and it can now only be found with any sort of frequency on the islands of Roaringwater Bay off Cork's west coast.

Yellow Bartsia, Parentucellia viscosa

All of which means I was very surprised and delighted to see two plants at a disused quarry just 17 km from Cork city center, the same quarry mentioned in my previous post on the Red Veined Darter. The plants were at the side of what was once the road leading to the main quarry, their wonderful cascade of yellow flowers immediately standing out from the surrounding scrub. The discovery of this scarce native in such an undisturbed demonstrates how our ever decreasing biodiversity could be maintained by the thoughtful management of our surroundings.

References:

1. O'Mahony, 2009. Wildflowers of Cork City and County pp. 97-99

Red Veined Darter at the Quarry

Female Red Veined Darter, Sympetrum fonscolombii

Human activity often leads to dramatic changes in our landscapes (1). These changes in turn can lead to often irreversible damage to our freshwater habitats. The building activity in Ireland during the boom in the 2000's involved drainage and development of sites that directly and indirectly lead to the destruction of many of the countries wetlands habitats. The crazed excesses of the so called "Celtic Tiger" are not wholly to blame however, as wetland destruction has been a feature of the Ireland's changing ecology for some years. For example the extensive wetland complex located around the Douglas and Tramore rivers near Cork city was replaced with the municipal dump for over 20 years. Such destruction generally leads to a homogenisation of biodiversity and the local extinction of many plants and animals (1).

Ballyhemiken Quarry

However this is not always the case. Sometimes human induced changes on the landscape have a positive effect on biodiversity. A prime example of this is unused quarries. When in use, water entering these sites is drained or pumped away. When no longer in use, this water is allowed to collect, forming wetlands that are not naturally present on Ireland (2). One such site is located in Ballyhemiken, a townland about 17 km from Cork city center. Unused for a number of years, this quarry has many shallow pools that provides the perfect habitat for odonates. A number of species have been recorded here, namely Beautiful Demoiselle (Calopteryx virgo), Emerald Damselfly (Lesta sponsa), Variable Damselfly (Coenagroin pulchellum), Common Blue Damselfly (Enallagma cyathigerum), Common Bluetip (Ischmura elegans), Large Red Damselfly (Pyrrhosoma nymphula), Migrant Hawker (Aeshna mixta), Emperor Dragonfly (Anax imperator), Four Spotted Chaser (Libellula quadrimaculata), Ruddy Darter (Sympetrum sanguineum), Black Darter (S. danae) and Common Darter (S. striolatum) (2).

Shallow Pond at Ballhemiken Quarry

On a recent visit to the quarry I was lucky to spot several Red Veined Darters (S. fonscolombii). This is a rare sighting for Ireland, as it is only seen here as a migrant, and seldom at that with only twenty records for Ireland, mostly near the coast. As far as I can tell, the record reported here is the westernly most sighting for S. fonscolombii in Ireland. All individuals were female, and two consecutive visits showed no males. They were very wary and took to wing upon my approach, flying a short distance before alighting on the surrounding Yellowworts, mint, low growing willow, Reed Mace and rushes. When undisturbed, the females congregated around shallow pools, some of which had dried up.

Female Red Veined Darter, Sympetrum fonscolombii

There are no record of S. fonscolombii ever breeding in Ireland, however in Britain there has been an increase in numbers breeding. It is predicted that Ireland may follow suit and the numbers of sightings may increase in the future (3).

Female Red Veined Darter, Sympetrum fonscolombii

References:

1. Dolný and Harabiš, 2012. Biological Conservation 145 pp. 109-117
2. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies p. 391
3. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies pp. 301-305

Perching for Prey

Four Spotted Chaser, Libellula quadrimaculata

Other than the ubiquitous Common Darter (Sympetrum striolatum), probably the most common dragonfly encountered in Ireland is the Four Spotted Chaser (Libellula quadrimaculata). This is due to its incredible aggressive behaviour. Both males and females move with an almost frantic speed around their territory and will challenge and fight any other odonates that encroach (1). The individuals pictured were observed around a c. 20 x 10 m pond in a dune slack which was 1 m at its very deepest. The pond had cluster of low growing willow (1 m above the waterline at its highest) at its center, ideal for the dragonflies to perch. L. quadrimaculata was observed to patrol the pond at high speed and challenge both the S. striolatum and Blue Emperors (Anax imperator) that were also present at the pond. A. imperator is considerably larger than L. quadrimaculata, but this did not deter it from the challenge. L. quadrimaculata was also seen to patrol the areas bordering the pond and to chase prey. One individual was seen to catch and eat a Comon Blue butterfly (Polyommatus icarus), taking the prey to the grasses in the surrounding dunes to consume it, as is illustrated in the photograph. After patrolling, L. quadrimaculata was seen to perch either among the willow in the middle of the pond or among the grasses in the surrounding dunes.

Four Spotted Chaser, Libellula quadrimaculata, feeding on a Common Blue butterfly, Polyommatus icarus

When perching, L. quadrimaculata held their bodies at a seemingly awkward angle (often 45°) in relation to the perch, even though resting their abdomens against the perch was often an option. The reason for this is not related to the animals body , but to its eyes. The compound eye of odonates, and many other insects, can be divided into dorsal and ventral areas where the structure of the fovea varies (2). In many odonate species, the different areas of the eye are quite easily distinguished from each other, with the dorsal side being much lighter in colour due to the presence of screening pigments (3). The dorsal fovea exhibits a high spatial resolution as well as a high degree of sensitivity to short wave resolution. This makes it ideally suited to the detection of prey flying against a blue sky. Therefore L. quadrimaculata perches in such a way that its dorsal fovea is exposed to the maximum amount of blue sky (4).

References:

1. Nelson and Thompson, 2004. The Natural History of Ireland's Dragonflies pp. 259-267
2. Kral, 2002. European Journal of Entomology 99 pp. 1-4
3. Labhart and Nilsson, 1995. Journal of Comparative Physiology 176 pp. 437-453
4. Sauseng et al., 2003. European Journal of Entomology 100 pp. 475-479

Common Blue Butterfly Second Brood

Second brood male (top) and female Common Blue butterfly (Polyommatus icarus), mating

In June, I reported on the first brood of the Common Blue butterfly (Polycommatus icarus) in Ireland, with an example of a mating pair. As was reported then, P. icarus has a second brood in August/September (1) and the butterfly can now be seen throughout the Irish coast, but also inland where its food plant, Common Bird's Foot Trefoil grows. The mating pair pictured were seen at some coastal dunes on the south coast. At least 6 other individuals were also seen in the vicinity.

Second brood male Common Blue butterfly (Polyommatus icarus)

References:

1. Nash et al., 2012. Ireland's Butterflies A Review pp. 156-158

Shortlisted for Blog Awards Ireland 2012

The Blog Awards Ireland Shortlist has just been announced - and 21stcenturynaturalist is on the shortlist for Best Science / Education Blog! Thanks for all your support! Again, results will be announced at the Blog Awards Ireland 2012 ceremony on the 13th of October.

Also, 21stcenturynaturalist is now on Facebook, so if you are interested in further natural science features and pictures, you can join us here.

Roads for the Ringlet

The Ringlet, Aphantopus hyperantus

As a wet, wet summer turns to autumn, one of the butterflies that remained flying despite of the rain will soon be gone until next year. The Ringlet (Aphantopus hyperantus) is on the wing from mid-May to the beginning of September in Ireland, but is most populous from the start to the middle of July. It is one of the most common species in Ireland and its preference for damp areas and ability to continue flying in light rain (1), unlike most other butterflies, means that this summer it was the species I personally encountered most often. Its larval food plants are almost exclusively grasses, such as Cocksfoot and False Brome, and it is around such grasses that adults are most likely to be encountered (1).

The Ringlet, Aphantopus hyperantus

Unfortunately, changes in agricultural practices and development have lead to a destruction of the semi-natural grassland habitats where these plants thrive, putting pressure on populations of A. hyperatus. Not all such development is without some benefit, however. Roadside verges and intersections have become home to many of the plant species associated with these habitats (2). It has been shown in a study on Finnish roads that the correct management of these areas through practices such as mowing can maintain populations of A. hyperantus and provide an alternative habitat for the butterfly (2). Intensive mowing should be avoided and mowing in mid-summer should only take place if road safety dictates. Even then only partial mowing in mid-summer is preferable, with a total mowing in late summer.

References:

1. Nash et al., 2012. Ireland's Butterflies a Review pp. 205-207
2. Valtonen and Saarinen, 2005. Annales Zoologici Fennici 42 pp. 545-556

Strawberry Trees Forever

Flowers of the Strawberry Tree, Arbutus unedo

As an island, Ireland has less plant species than Britain, which in turn has less than continental Europe. It would stand to reason then to expect all the botanical species present here to be present in Britain, and then some. Yet this is not the case, with Ireland being home to a number of plants not present in the wild in Britain. There are three main classes of such plants, based on the regions that they are characteristic of, namely the Atlantic flora, the American flora and the Mediterranean-Atlantic flora (1). Of the last group, the most intriguing member has to be the Strawberry Tree, Arbutus unedo. As a member of the Ericacea family, it has wonderful bell shaped, heather-like flowers. The fruit give the plant its common name, being shaped like strawberries. These take a year to reach their full ripeness, and so the tree often has both flowers and fruit present, as was the case in the specimen pictured. It is of common occurrence throughout the Mediterranean (to the extent that it features on the coat of arms of the city of Madrid) where it tends to grow as a low shrub. Its range in Ireland extends along the west coast, with extant sites in Kerry, West Cork and Sligo (1). Here, it is more likely to be found as a tree and can grow up to 10 meters in height (2). A. unedo seemingly had a much wider distribution in Ireland in the past as it was a protected species under Brehon Laws here in the eight century. It was then known as "Caithne" and this is still present in many Irish place names (1).
 

Strawberry Tree, Arbutus unedo

So why is this plant present in Ireland but not Britain? The theory behind Ireland's floral distribution is that the communites we have with us now began arriving after the last major glaciation event c. 15,000 years ago from mainland Europe. Since sea levels were much lower at that time, the coast lines of Ireland and Britain must have been very different from what they are now and possible landbridges between these two islands and Europe may have existed (3). The exact nature of these is considered to be a possible reason for the presence of A. undeo in Ireland but not Britain. Post-glacial movement by human populations may similarly have brought the tree to Ireland, bypassing Britain (4).

Fruits of the Strawberry Tree, Arbutus unedo

However, the idea of Ireland being a clean slate for plant species after the last glaciation event has been challenged by recent genetic evidence from the Fringed Sandowort (Arenaria ciliata). This low growing plant, found in mountainous habitats is found in only one location in Ireland, on top of the mountain Ben Bulben in Co. Sligo. Analysis of a number of European populations has shown that the Irish plants in this location survived the last glaciation event and have been present here for at least 100,000 years (5). The presence of such a refuge indicates that other areas in the country may have similarly avoided the ice sheet, providing the possibility that A. unedo may have been in the country for a similar length of time. There is also the possibility that A. unedo was present in Britain prior to the last major glaciation event, but the next either left no refuges as were left in Ireland or, more likely, left refuges that were in areas where no populations of A. unedo existed.
 

Strawberry Tree, Arbutus unedo

And yet all of this is supposition and the real origins of A. unedo in Ireland remains a mystery. This may become lessened in the near future, however, as a research project being spearheaded by Colin Kelleher of the Irish National Botanic Gardens is sampling A. unedo plants from Ireland and from areas within its European to try to elucidate what the relationships are between populations. Results of this work will certainly help to bridge some of the gaps in our knowledge of this wonderful plant.

References:

1. O'Mahnoy, 2009. Wildflowers of Cork City and County pp. 118-138
2. Sterry, 2004. Collins Complete Guide to Irish Wildlife p. 188
3. Pilcher and Hall, 2001. Flora Hibernica pp. 1-17
4. Teacher et al., 2009, Heredity 102 pp. 490–496
5. Dang et al., 2012. Molecular Ecology Resources 12 pp. 894–908