Wednesday, March 2, 2022

Unarmed by an Unarmed Stick Insect

Unarmed Stick Insect, Acanthoxyla inermis

The routes of introduction of non-native species into the island of Ireland are many, with the vast majority of those in the past 200 years being mediated by human activities. Many have been deliberate, with the species' adaptability to Irish conditions often leading to their proliferation, such as the catastrophic establishments of the invasive plants Rhododendron ponticum, Japanese Knotweed (Reynoutria japonica) and Winter Heliotrope (Petasites fragrans). Other instances have been accidental, and the happenstance of their presence have been as surprising as the species themselves.

One such example is the Unarmed Stick Insect, Acanthoxyla inermis. While the order of stick insects is distributed worldwide, Europe has only 17 species of native stick insects, with none being present on the island of Ireland. That is, however until late in the 19th century when Samuel Thomas Heard began to lay out his garden in Rossdohan Island in Kenmare, Co. Kerry.

Born in Cork, Samuel was an Indian Army Surgeon-Major until his retirement, when he bought the island of Rossdohan in Kenmare Bay in 1873. He proceeded to turn this uninhabited island of closely cropped vegetation into an exotic garden. His interest in gardening began in his youth, with many collections begin amassed in places such as Fota, Castlemartyr and Doneraile near his family seat at Ballintober, near Kinsale Co. Cork. This was further fuelled in Paris, a city he spent some time in upon graduating in medicine. There, the experiments in bedding out subtropical plants in the city's parks by Jean-Pierre Barillet-Deschamps were causing a stir worldwide. During his time in India, Samuel also became familiar with the Madras Horticultural Gardens. However probably his greatest influence when it came to laying out his garden in Rossdohan was his wife Kate Bradley, whom he married in 1862. Kate was from New South Wales in Australia and this inspired the import of many Australasian florae. It was the importation of plants and soil from New Zealand that is linked with the establishment in the area of the Unarmed Stick Insect, A. inermis. This  the source of which was Treseders Nursery in Truro, England. James Treseder took over the running of the nursery in 1820 and quickly developed the business. His sons all unsuccessfully tried their luck in the Australian gold fields but soon gave this up to run a successful nursery in Sydney. James' son John began the export to Europe of plants from Australia, New Zealand and Tasmania that he, correctly, though would be hardy enough to withstand the different climate. 

A. inermis, along with many other species of Phantasmids, reproduces parthenogenetically with males being virtually non-existent in established colonies. Several hundred eggs are laid by females in summer and early autumn so plant and soil material containing these can readily establish a new colony if transported elsewhere. The adults are polyphagious and slow moving with therefore little inclination to move elsewhere which means that colonies tend to be localised. This is very much the case with the population in Ireland, which is restricted to pockets around Kenmare. These areas are either associated with materials source directly from New Zealand (such as the colony in Derreen Gardens) or with the taking of material from Rossdohan and Derreen: the house at Rossdohan was burned down in 1923 and the estate all but abandoned for a period after Irish independence, leading to plants being taken from there by locals. A. inermis is now established at a garden centre in Kenmare, increasing the likelihood that its range will be extended further as material is disseminated from there.

While I was aware of its presence in the Kenmare area, it did come as a pleasant shock for me to find an individual in a suburban garden in Cork City. On the 16th of March, 2021, I found a juvenile wandering about some potted strawberry plants near some brambles in my back garden. The size of the individual and the time of the sighting indicates that it had hatched close-by, most likely from material source from Kenmare. The garden in question is closely bordered by a number of others all of which share the same bramble hedges. 

Juvenile Unarmed Stick Insect seen in Cork City

A. inermis grows to 90-125mm in length making them easily the largest insects on the island of Ireland. The body is smooth, although a few small tubercles may be present. The cerci are rounded. Body colour varies from green to brown, with brown specimens ranging from yellow to almost black. They feed on various members of the Rosaceae family, of which at least two were present near where this juvenile individual was found. It displayed a trait for which the A. inermis is well known, namely swaying from side to side as it moved. This is thought to aid camouflage by coping the movement of foliage in the wind.


Lee, M. (2006) The Stick-insects of Great Britain, Ireland and the Channel Isles. Phasmid Study Group Newsletter 107: 20‒27
Lee, M. (2007) The Naturalised Stick-insects in South-west England. Atropos 32: 31-37
Malins, E. and Bowe, P. (1980) Irish Gardens and Demesnes from 1830 Barrie & Jenkins

Monday, April 27, 2020

Moth Eared

As the summer is about to begin, one of the large lepidoperan larvae currently visible is that of the Lesser Yellow Underwing Moth, Noctua comes. These larvae have emerged from an overwintering period and will restart feeding on the wide variety of plants that are typically consumed by this polyphagous species. Adults emerge from July to mid autumn from pupation in the soil, in an earthen chamber. While generally nocturnal, the larva can be seen in suburban gardens due to their varied diet which includes weeds and commercial bedding plants.
Lesser Yellow Underwing, Noctua comes, larva

The adults get their name from their orange-yellow hind wings that re generally not visible when at rest. While it is widely distributed throughout Europe, it is also established in North America where it was first recorded in 1984. Since then, it has proved to be a pest of grapes and tobacco which the larvae feed on to often quite damaging result.
As a night flying moth, N. comes is a major component of the diet of the European bat fauna. Hunting by echo location, the bats obviously emit sounds that the insects either cannot detect or do not respond to. However, often bats are ringed as part of conservation methods and sometimes there may be two rings close to each other. When these rings touch in flight a sound is created which alerts the moth, actuating evasive manoeuvers.

Arlettaz et al., Animal Behaviour 57 1999 pp. 829-835
Alford, Pests of Fruit Crops: A Color Handbook 2007 pp. 369-370
Copley and Cannings, Journal of the Entomological Society of British Ccolumbia 102 2005 pp. 83-84

Thursday, January 7, 2016

The First Irish Trees

The wettest winter on record has finally brought us a cold snap. Temperatures that were touching the mid-teens have finally reverted to the winter norm and started to approach zero, bringing with them the long missed pleasure of the crisp, dazzlingly bright morning. Blue skies frame naked trees, an architecture that is all too absent from the Irish landscape. Despite having a reputation for being a verdant land, Ireland has long had the lowest area of forestry in the EU. Only 10.5% of the country is covered in forest (1). And while this is estimated to be at its highest level in 350 years (in 1928 the percentage cover was a measly 1.2%), more than three quarters of this are non-native coniferous plantations. The methods of cultivation of these forests, namely close and intensive planting which discourages lateral branching to maintain the bulk of the timber in one solid piece, renders such forests as areas of monoculture (predominantly Sitka Spruce, Picea sitchensis (1)) with a very low level of biodiversity. What we would refer to as native woodlands account for only a small fraction of Irish forests, but even calling them native is rather misleading as many of these are also themselves deliberately planted, such as Powerscourt estate in Co. Wicklow which dates to the first half of the 18th century (2). In truth, even trees in Ireland unmolested by humankind can only date from the after the most recent global glaciation period, when the vast majority of the island of Ireland was covered in ice.

Yet the history of Irish trees does extend back beyond the ice age, back into the mists of the Devonian period, some 350 million years ago when Ireland, as we know it now, was to be found near the equator. The present Irish landmass which had been previously divided by an ocean, now began to develop small lakes (3). These were surrounded by what many people believed to be the first tree, Archaeopteris, specifically Archaeopteris hibernica. Paleobotanical evidence points to plant species prior to this as tending to be ground covering. This was also thought of A. hibernica when it was first discovered, as the leaf like fronds were described separate to its woody trunk (called Callixylon) (4). This Callixylon could grow to impressive sizes, with fossils one meter in diameter and ten meters in length often being unearthed. Yet it was incorrectly identified as a Late Devonian conifer in when described in 1911. It took nearly 50 years for the link between Callixylon and Archaeopteris to be made. A chance discovery of a section of Archeaopteris with parts of the woody stem attached by Charles Beck allowed both Archaeopteris to be given the title of tree and the establishment of the extinct group of plants the progymnosperms (4). He was able to section an immaculately preserved sample and show that the attached wood was indeed Callixylon.

Archaeopteris hibernica fossil

Archaeopteris plants were non-seed bearing, producing spores much like modern day ferns on fronds that were arranged on branches. These extruded horizontally and in a helical pattern from a single trunk (5). Branching patterns were quite complex and longer living in comparison to other plants at the time allowed Archaeopteris to occupy more space, more efficiently. Indeed, it shares many of these features phylogenetically with modern seed plants (5). Its success was such that it was the pre-eminent vegetation of forests in the Late Devonian period though to the Mississippian.

Recreation of Archaeopteris hibernica

In old Devonian Ireland, A. hibernica was dominant. Wonderfully preserved examples of the fronds have been recovered from the Devonian-Carboniferous Kiltorcan Formation in Co. Kilkenny. Study of this area reveals a swamp like environment, with meandering streams feeding into pools surrounded by dense growth of A. hibernica (6).

  1. Teagasc.,2014. Irish Forests -  Annual Statistics.
  2. Pilcher and Hall, 2004. Flora Hibernica. Collins Press, Cork.
  3. Clayton et al. 1979. Journal of Earth Sciences. Vol. 2, pp. 161-183.
  4. Bora, 2010. Principles of Paleobotany. Mittal Publications.
  5. Meyer-Berthaud et al. 1999. Nature 398 pp. 700-701.
  6. Jarvis, 2000. Geological Society, London, Special Publications 180 pp. 333-341.

Tuesday, February 10, 2015

A Barrel of Pain

A common jellyfish found off the Irish coast, the Barrel Jellyfish, Rhizostoma pulmo, has quite an extensive range. It is distributed in the Irish Sea, the Bay of Biscay, the North Sea, the Black Sea and is found extensively throughout the Mediterranean, so much so that it commercially fished (albeit on a small scale) off the coast of Turkey (1). It has even been found off the coast of Pakistan, where a record again associated with commercial fishing of the jellyfish was reported in 2007 (2). It is quite a striking animal, with a robust appearance and an ethereal, blushed mauve coloration. Despite their their relatively large size (up to 60 cm in diameter), and possibly due to an underreporting of cases, it was assumed for many years that this species was harmless to humans (3). However, this is no longer the case (4).
Barrel Jellyfish, Rhizostoma pulmo
R. pulmo, like all jellyfish, is contradictory animal being as it is a relatively simple organism with quite a complex life cycle. This begins with the production of pelagic planulae by sexually mature adult that settle as polyps on hard substrates on the sea bed. These then metamorphose into strobilae, which reproduce asexually to form 8-rayed ephyrae. Up to eight of these may be produced per strobila. These detach to roam the pelagic zone where they mature into the adult medusae (5).
Barrel Jellyfish, Rhizostoma pulmo
Adults produce Rhizolysin, a cytolysin, from their nematocysts for subduing prey. This has cytotoxic, hemolytic and clastogenic activity against human cells, which leads to irritation and the production of lesions upon contact with the skin (4, 6). Such lesions last for a few hours, but the subsequent pain can last for a period of days, causing considerable discomfort.

  1. Omori & Nakano, 2001. Hydrobiologia 451 pp. 19–26.
  2. Muhammed & Sultana, 2007. JMBA2 Biodiversity Records (Published on-line) pp. 1–3.
  3. Addad et al, 2011. Marine Drugs 9 pp. 967-983.
  4. Kokelj & Plozzer, 2002. Contact Dermatitis 46 pp. 179-180.
  5. Fuentes et al, 2011. Marine Biology 158 pp. 2247-2266.
  6. Allavenaa et al, 1998. Toxicon 36 pp. 933–936.

Wednesday, February 13, 2013

A Personable Little Bug

Firebug, Pyrrhocoris apterus
As I progress through life, my opinions and outlook has changed, in a way that I would like to think is more mature. One thing that has not changed about me though is how I tend to be led by my stomach. When I'm hungry I need to eat. Otherwise I get irritable and withdrawn. People often mistake it for some deep troubles within me, but its just a primal need to fill my belly. However I have learned to deal with it though in the simple possible way: regular eating. And sometimes the joys are not only culinary. Recently hunger grabbed me in Cork city and I made my way into the nearest cafe, a wonderful vegan eaterie (I'm an omnivarian, I'll eat anything at all, and don't mind if there is no meat with my meal as many carnivores often do). While tucking into my felafel and salad (which was smashing, if you were wondering), my eye was caught by something small and red on the Crassula plant that was in front of me. I was a Firebug (Pyrrhocoris apterus), a species that if not native to Ireland and a species that, as far as I can ascertain, has not been reported here before. The mature adult had been there at least one week, according to the staff, and may have arrived in one of the many deliveries of vegetables that they receive every week from continental Europe where P. apterus has its base. A flightless bug, it feeds on Lime trees and tree-mallows, and is most associated with its swarming behaviour whereby numerous individuals clamour together. Its common name, Firebug comes from its wonderful crimson colour that contrast wonderfully with the black markings on its abdomen creating an almost face-like effect.

As with all insects, P. apterus goes through a series of ecdyses through out its life, five in all from hatching to adulthood. Interestingly it has been shown that at different stages of moult, individuals show distinctly different personalities. Larvae differed from adults in general in that they were bolder, explored their environment more thoroughly and seemed to be more active before final ecdysis (1). This raises the intriguing concept of personality differences between individual organisms as inherited traits. In an environment, it is argued, if fitness payoffs are dependent on an organisms behavioural history and the frequencies of competing strategies then personality differences can be selected for (2). It certainly is an interesting idea and is supported by evidence from diverse sources as lab rats, where heavier newborns are braver and more explorative (3), field crickets, where personality changes at maturity (4), and squid, where size determines personality. How exactly the behavioural changes take place in P. apterus is not know, but it may be due to hormonal reorganisation.
So perhaps my apparent grouchiness due to lack of food is just my inheritance...

  1. Gyuris et al., 2012. Animal Behaviour 84 pp. 103-109
  2. Dall et al., 2004. Ecology letters 7 pp. 734-739
  3. Rödel and Meyer 2011. Developmental Psychobiology 53 pp. 601-613
  4. Niemelä at al., 2011. Functional Ecology 26 pp. 450-456
  5. Sinn and Moltschaniwskyj, 2005. Journal of Comparative Psychology 119 pp. 99-110

Thursday, December 27, 2012

A Mayfly in December

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.
SpeciesConservation Status
Siphlonurus armatusCR
Baetis atrebatinusEN
Ephemerella notataEN
Rhithrogena germanicaVU
Procloeon bifidumVU
Leptophlebia marginataVU
Kageronia fuscogriseaNT
Ameletus inopinatusNT
Baetis fuscatusdd
Alainites (Baetis) muticuslc
Baetis rhodanilc
Baetis scambuslc
Baetis vernuslc
Caenis horarialc
Caenis luctuosalc
Caenis macruralc
Caenis rivulorumlc
Centroptilum luteolumlc
Cloeon dipterumlc
Cloeon similelc
Ecdyonurus disparlc
Ecdyonurus insignislc
Ecdyonurus torrentislc
Ecdyonurus venosuslc
Electrogena lateralislc
Ephemera danicalc
Heptagenia sulphurealc
Leptophlebia vespertinalc
Paraleptophlebia cinctalc
Rhithrogena semicoloratalc
Serratella ignitalc
Siphlonurus alternatuslc
Siphlonurus lacustrislc

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).

  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

Wednesday, December 26, 2012

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).
  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