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Occurrence, reproductive rate and identification of the non-native Noble false widow
spider
Steatoda nobilis
(Thorell, 1875) in Ireland
Author(s): Michel M. Dugon, John P. Dunbar, Sam Afoullouss, Janic Schulte, Amanda
McEvoy, Michael J. English, Ruth Hogan, Collie Ennis and Ronan Sulpice
Source:
Biology and Environment: Proceedings of the Royal Irish Academy,
Vol. 117B, No.
2 (2017), pp. 77-89
Published by: Royal Irish Academy
Stable URL: http://www.jstor.org/stable/10.3318/bioe.2017.11
Accessed: 18-09-2017 20:22 UTC
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77
OCCURRENCE, REPRODUCTIVE RATE
AND IDENTIFICATION OF THE
NON-NATIVE NOBLE FALSE WIDOW
SPIDER STEATODA NOBILIS (THORELL,
1875) IN IRELAND
Michel M. Dugon and John P. Dunbar, with Sam Afoullouss,
Janic Schulte, Amanda McEvoy, Michael J. English, Ruth Hogan,
Collie Ennis and Ronan Sulpice
ABSTRACT
The noble false widow Steatoda nobilis (Thorell, 1875) has established thriving populations in
urban centres throughout England and Wales since it was accidentally imported from the Canar y
Islands and Madeira to Britain over a centur y ago. In recent years, Steatoda nobilis has colonised
parts of Wester n Europe, California, Chile and the Middle East. In Ireland, Steatoda nobilis was
fi rst recorded in 1999 from a single location in Co Wicklow. The present study examines the
current range and main habitats of Steatoda nobilis in Ireland and assesses its potential as an inva-
sive species by documenting its reproductive rate. Additionally, we present photographic material
illustrating the intraspecifi c phenotypic variations exhibited by Steatoda nobilis to assist in correct
identifi cation of this species by the public. Our data shows that Steatoda nobilis is an ext remel y pr o-
lifi c, resilient species with distinct synanthropic affi nities. This species currently occurs in at least
sixteen Irish counties with the largest populations observed in the greater Dublin area, where it
has become widespread in buildings and on street furniture. Steatoda nobilis seems to be currently
absent from natural, undisturbed habitats such as woodlands, bogs and grassland. We suggest that
due to its comparatively fast reproductive rate, long life span and year-round activity, Steatoda
nobilis might have a detrimental impact on native urban-dwelling spiders.
INTRODUCTION
The fi rst Ir ish record for the noble false widow
spider Steatoda nobilis (Thorell, 1875) occurred in
Bray, Co Wicklow, in 1998 (Nolan 1999). This alien
species is of particular interest in Great Britain and
in Ireland as it has been involved in the only case
of systemic envenomation (steatodism) reported in
these islands (Warrell et al. 1991). Additionally, stud-
ies suggest that Steatoda nobilis might have a negative
impact on populations of native arthropods in areas
it has colonised (Kulczycki 2012).
The geographical expansion of Steatoda nobilis
has been fairly well documented for over a century,
thanks to its relatively large size, conspicuous mark-
ings and superfi cial resemblance to the black widows
of the genus Latrodectus (Walckenaer 1805). Steatoda
nobilis is thought to originate from the Atlantic ar-
chipelagos of Madeira (Thorell 1875) and the Ca-
naries (Bristowe 1929). In 1879, Steatoda nobilis was
recorded for the fi rst time outside its native range;
Rev. Pickard-Cambridge identifi ed a sub-adult
female collected a few years earlier by Rev. Ham-
let Clark near Torquay, Devon (Pickard-Cambridge
1879). This confi rms that Steatoda nobilis reached the
British Isles—at least as an occasional visitor—well
before the turn of the twentieth century. In 1906,
A.R. Jackson came into the possession of at least one
adult female collected by a third party on a cliff in
southern England, away from man-made structures
(Jackson 1907). Jackson concluded that the specimen
was unlikely to be a mere alien ‘visitor’, and implied
that a population may have already been established
in southern England by the early 1900’s. Referring
to Pickard-Cambridge’s work, Bristowe (1929) sug-
gested that Steatoda nobilis may have been imported
occasionally from the Canary Islands in shipments of
bananas but rejected the idea that Steatoda nobilis had
established sustainable colonies at the time of publica-
tion. Steatoda nobilis was later recorded at closer inter-
vals in the southern half of Britain: Hampshire (Jones
1979; Jones 1987), Dorset (Snazell and Jones 1989),
Received 02 February
2017. Accepted 26
July 2017. Published
04 September 2017.
Michel M. Dugon
(corresponding
author; email:
Michel.dugon@
nuigalway.ie), Room
214 - Zoology,
The Ryan Institute,
National University
of Ireland, Galway,
Co Galway, Republic
of Ireland; John
P. Dunbar, Sam
Afoullouss, Janic
Schulte, Amanda
McEvoy, Michael
J. English, Ruth
Hogan, Collie Ennis
and Ronan Sulpice,
Venom Systems and
Proteomics Lab,
School of Natural
Sciences, National
University of Ireland
Galway.
Cite as follows:
Dugon, M., Dunbar,
J.P., Afoullouss, S.,
Schulte, J., McEvoy,
A., English, M.J.,
Hogan, R., Ennis,
C. and Sulpice, R.
2017 Occurrence,
reproductive rate
and identi cation of
the non-native Noble
false widow spider
Steatoda nobilis
(Thorell, 1875) in
Ireland. Biology
and Environment:
Proceedings of the
Royal Irish Academy
2017. DOI: 10.3318/
BIOE.2017.11
DOI: https://doi.org/10.3318/BIOE.2017.11
BIOLOGY AND ENVIRONMENT: PROCEEDINGS OF THE ROYAL I RISH A CADEMY, VOL. 117, N O. 2, 77–89 (2017). © ROYAL IRISH A CADEMY
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BIOLOGY AND ENVIRONMENT
78
tweezers or a Katcha™ Bug Buster Spider Vacuum
and then placed in 50ml falcon tubes. Locations
were systematically recorded. In those instances
when they occurred, predation events involving
Steatoda nobilis were recorded and photographed.
The collection of live specimens for lab-based
experiments took place after sunset (when Steatoda
nobilis is most active) in the larger Dublin area
between September 2015 and October 2016.
Online-based records
Records of Steatoda nobilis sightings were compiled fol-
lowing a web search on four wildlife recording websites
(brc.ac.uk/irecord/; biodiversityireland.ie; ispotnature.
org; nbnatlas.org/) and two online social media groups
(facebook.com/groups/BritishSpiderIdentifi cation/;
facebook.com/groups/insectsinvertebratesire/).
Webpages were searched using the following key
words: Steatoda, nobilis, false widow, spider, Theridiidae,
cobweb, comb-footed. A list of messages containing
positive photographic identifi cation of Steatoda nobilis
was compiled. Photographers were contacted by the
authors to confi rm recorded sightings and to obtain
photographic voucher material. Additionally, the au-
thors posted public messages on the two social media
webpages aforementioned, inviting group members
to submit photographic material of new sightings.
Records were subsequently compiled and locations
were mapped to their nearest 10km grid using ArcGIS
v10 (ESRI, California, USA).
REPRODUCTIVE STUDY
Previous studies (Hann, 1990) suggest that the high
reproductive rate of the invasive Steatoda capensis
(Hann 1990) in New Zealand is a contributing
factor in the displacement of the native Latrodec-
tus katipo (Powell, 1871). Following Hann’s lead,
we investigated the reproductive rate of Steatoda
nobilis in captivity and compared it with existing
data on the reproductive rate of the missing-sec-
tor orb weaver Zygiella x-notata (Clerck, 1757), a
common urban dweller in Ireland (Wherry and
Elwood 2009).
Steatoda nobilis caught in Co Dublin were kept
individually in 80mm x 50mm cylindrical plastic
containers with shredded paper as substratum. Spi-
ders were stored in chest incubators at a constant
20°C, watered and fed weekly on a diet of commer-
cially available crickets (Gryllus assimilis, Fabricius,
1775) and fruit fl ies (Drosophila melanogaster, Meigen,
1830). Each spider was individually coded to facili-
tate records of egg-laying. Egg sacs were consistently
removed from the mother in the 24 hours follow-
ing egg-laying. Each egg sac was individually coded,
measured and incubated at 20°C in a 25ml falcon
tube containing wet cotton to avoid dehydration. Egg
sacs were either left to hatch or processed for further
developmental investigations. Hatchlings were kept
Essex (Smith 1992; Merrett 2001), Sussex (Warrell
et al. 1991), Warwickshire (Bate 2005), Glamorgan-
shire (Jones, 2006), Leicestershire (Daws 2008) and
Lincolnshire (Binding 2014). Further afi eld, the dis-
tribution range of Steatoda nobilis has been continu-
ously expanding since the turn of the twenty-fi rst
century. Steatoda nobilis has become widespread in
coastal urban centres in France (Kovoor and Munoz-
Cuevas 2000), Belgium (Van Keer 2010), Italy (Kul-
czycki 2012), Spain (Déjean 2013), Portugal (Cardoso
2000), California (Vetter and Rust 2012; Vetter et al.
2015) and Chile (Taucare-Rios et al. 2016; Faúndez
and Téllez 2016). Eastward, Steatoda nobilis has been
observed in Germany (Reiser 2013), Turkey (Turkey
and Mergen 2007) and as far as Iran (Zamani et al.
2015).
Although Steatoda nobilis is thought to have
spread in many parts of Ireland since Nolan’s origi-
nal report (1999), the occurrence and the ecological
impact of this species at the national level have not
been assessed yet. The aims of the present study are
threefold: 1) assess if Steatoda nobilis has expanded
its Irish range since it was fi rst recorded; 2) doc-
ument the reproductive rate of Steatoda nobilis; 3)
document the intraspecifi c phenotypic variations
exhibited by Steatoda nobilis in Ireland to assist in
correct identifi cation by the public.
MATERIALS AND METHODS
DISTRIBUTION STUDY
New distribution records were compiled either di-
rectly by the authors during habitat surveys or by
screening wildlife-recording and social media re-
sources for photographic records posted online by
amateur arachnologists.
Field inspection and spider collection
Surveys took place between September 2014 and
February 2017 as part of a series of student-led
arthropod surveys held by the National University
of Ireland Galway Discipline of Zoology. Urban-
ised areas, woodlands, coastal habitats, bogs, mead-
ows and a cave system were inspected across nine
Irish counties for the presence of alien arthropods,
including Steatoda nobilis. Depending on habitats,
survey methods included visual inspection, net
sweeping, beating trays, pitfall traps and cryptozoic
traps. The latter consisted of 40cm-wide pieces of
cardboard wrapped around tree trunks and checked
weekly for a period of three weeks. Coordinates,
habitats, dates and sampling methods for each sur-
veyed location are detailed in Table 1.
When sightings were made, the subsequent area
was extensively searched by the authors and Steatoda
nobilis were collected using either a pair of fl exible
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THE FALSE WIDOW STEATODA NOBILIS IN IRELAND
79
Table 1—Habitats surveyed for the presence of the noble false widow spider Steatoda nobilis. Surveys took place between September 2014 and
February 2017 across six Irish counties. Coordinates were obtained from the National Biodiversity Data Centre, Waterford (http://maps.
biodiversityireland.ie/#/Map). Cryptozoic traps refer to 40cm wide pieces of cardboard wrapped around ten tree trunks and checked weekly for a
period of three weeks. Pitfall traps consisted of fi ve plastic cups of 7.7cm diameter and 10.6cm height fi lled with a saline solution. Traps openings
were covered with plastic lids secured into the ground with two nails, leaving a 1cm gap between the rim of the cup and the lid. Pitfall traps were
relieved weekly for a period of three weeks. The Transect belt consisted in a 20m long ribbon laid on the fl oor. The survey area extended one meter
on each side of the ribbon, vegetation up to approximately 1.8m in height was searched. Surveys were typically two to two and a half hours long
and involved one to six surveyors. (*) Surveys / collection performed after sunset; all other surveys were performed during daytime.
Location Coordinates Habitats Sampling methods Number of visits / Sampling dates Specimens caught
Co Galway - Galway City
Docks
130127, 224953 Apartment complex
outdoors
Visual inspection First sighting in Galway
November 2011
1
Co Galway – Galway City
City centre
129986, 225191 Parking lots Visual inspection Three visits
September 2014
4
Co Galway - Galway City
Southpark
130005, 224475 Sandy shore / coastal
meadow
Visual inspection
Sweeping net
Three visits (weekly)
October 2014
0
Co Galway - Galway City
NUI Galway campus
129340, 225689 Mix trees / buildings Visual inspection
Cryptozoic traps
Three visits (weekly)
September–October 2014
0
Co Galway – Galway City
Terryland Forest Park
129863, 226223 Peri-urban mixed decidu-
ous woodland
Cryptozoic traps
Pitfall traps
Visual inspection
Sweeping net
Seven visits (weekly)
September–November 2014
0
Co Galway – Knocknacarra
Rusheen Bay
125847, 223820 Sandy shore / coastal
meadow
Visual inspection
Sweeping net
Three visits (weekly)
September–October 2014
0
Co Galway – Barna
Barna Woods
124380, 223775 Deciduous woodlands Cryptozoic traps
Pitfall traps
Visual inspection
Three visits (weekly)
September–October 2014
0
Co Galway - Barna
Barna bog
122467, 227026 Blanket bog Pitfall traps
Visual inspection
Visual inspection
Three visits (weekly)
September–October 2014
0
Co Galway - Monivea
Monivea Woods
153980, 236403 Mixed woodlands Cryptozoic traps
Pitfall traps
Visual inspection
Sweeping net
Three visits (weekly)
September–October 2014
0
154284, 236034 Thickets of Prunus lauro-
cerasus exclusively
0
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BIOLOGY AND ENVIRONMENT
80
Table 1 (Continued)
Location Coordinates Habitats Sampling methods Number of visits / Sampling dates Specimens caught
Co Galway – Coole
Coole Park
143731, 205117 Mixed deciduous and
coniferous woodlands
Cryptozoic traps
Pitfall traps
Visual inspection
Sweeping net
20m transect belt
Three visits (weekly)
September – October 2014
0
143387, 204757 Turlough shores /
meadows
0
Co Galway - Salthill
Quincentenary Rd
128344, 223833 Apartment complex
Indoors
Report from the public –
collected by MD
One visit (collection)
November 2014
1
Co Galway - Galway City
Newcastle Street
128915, 226361 Semi-detached houses
Indoors and outdoors
Report from the public –
collected by MD
One visit (collection)
March 2015 1
Co Galway - Galway City
Terryland Retail Park
129980, 226058 Industrial estate
Indoors and outdoors
Visual inspection Three visits (weekly)
September 2015 0
Co Galway - Oranmore
Gurraun North
137019, 226188 Peri-urban bungalow Visual inspection
Sweeping net
Three visits (weekly)
September– November 2015 0*
Co Galway – Oranmore
Claregalway Rd
138500, 227034 Peri-urban bungalow Visual inspection
Sweeping net
Three visits (weekly)
September– December 2015 0*
Co Galway – Oranmore
Tudor Vale
137936, 225423 Hotel complex
Outdoors
One visit
September 2016 4
Co Mayo – Ballina
Belleek Castle Park
125127, 320744 Mixed deciduous and
coniferous woodlands
Visual inspection
Sweeping net
20m transect belt
One visit
May 2015 0
Co Sligo – Ballimote
Kesh cave system
170587, 312149 Limestone cave system Visual inspection Two visits
June 2016 & January 2017 0
Co Roscommon - Ballymurray
Mote Park
190563, 261296 Mixed deciduous and
coniferous woodlands
Visual inspection
Sweeping net
20m transect belt
One visit
September 2015 0
Co Tipperary – Clogheen 195749, 113229 Farmland, inside dry shed Visual inspection One visit
October 2016 1
Co Longford –
Edgeworthstown
224682, 273918 Across the dashboard on
the registration plate, wing
mirrors and oil cap of a car
Visual inspection Two visits
October 2015 5
Outside between wall of
house and drain pipe
July 2016 1
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THE FALSE WIDOW STEATODA NOBILIS IN IRELAND
81
Table 1 (Continued)
Location Coordinates Habitats Sampling methods Number of visits / Sampling dates Specimens caught
Co Westmeath –
Mullingar
245211, 253612 Indoors, inside a garden
shed
Report from the public –
collected by JD
One visit (collection)
October 2016 3
Co Kildare – Maynooth
NUI Maynooth Campus
292997, 238528 Indoors on walls, outdoors
on windows, concrete and
steel structures
Visual inspection Four visits
August 2015 to September 2016 34*
Co Dublin – Tallaght 310309, 227410 Indoors under kitchen
units, inside garden shed,
greenhouse and outdoors
around windows
Visual inspection One visit
February 2016 20
Co Dublin – Tallaght
Tallaght Business Park
308322, 227041 Indoors Report from the public
Collected by MD and JD
One visit
February 2016 20
Co Dublin – Dublin City
Merrion St
316434, 233550 Metallic railing Visual inspection One visit
June 2016 2
Co Dublin - Clondalkin, Green
Isle hotel
306471, 229989 Outdoors on boundary
railings
Visual inspection One visit
Junes 2016 4
Co Dublin – Lucan public park 304694, 234684 Public park boundary wall
and railings
Visual inspection One visit
July 2016 54*
Co Dublin - Stephens Green 315880, 233507 Public park boundary
railings
Visual inspection One visit
July 2016 3
Co Dublin - Raheny 321695, 238343 Indoors on a blanket and
outdoors on garden wall
Visual inspection Two visits
August 2016
September 2016
1
4
Co Dublin - Lucan 305265, 234054 Inside and outside of
garden shed, along garden
walls and furniture
Visual inspection Eight visits
August 2015
October 2015
February 2016
March 2016
September 2016
October 2016
December 2016
February 2017
15
71*
50*
1*
150*
172*
1*
160*
Co Dublin – Bawnogue,
Clondalkin
305363, 231769 Outdoors - Inside and
outside a wheelie bin
Visual inspection One visit
October 2016 7
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BIOLOGY AND ENVIRONMENT
82
specimen. Four of the 32 locations surveyed by the
authors yielded single specimens and 14 yielded
multiple specimens. The remaining 16 locations
surveyed did not yield any specimen. At the na-
tional level, a majority of specimens were sighted
in coastal areas as opposed to the midland coun-
ties (Fig. 1). The authors observed mature Steatoda
nobilis throughout the year regardless of ambient
temperatures, both outdoors and indoors (Table 1).
STEATODA NOBILIS HABITAT
Urbanised areas, woodlands, coastal habitats, bogs,
meadows, turlough shores and a cave system were
investigated for the presence of Steatoda nobilis. Adult
specimens were exclusively found on steel, concrete or
timber structures in heavily urbanised areas. Such hab-
itats included sheds, steel fencing, concrete walls, cel-
lars, room ceilings, skirting boards and window ledges.
All locations surveyed in and around Dublin yielded
at least one specimen on each visit. Over a period of
18 months, 620 specimens were obtained from a single
row of semi-detached houses in Lucan, Co Dublin.
Meanwhile, not a single Steatoda nobilis was found in
the ten non-urbanised locations we surveyed.
A total of six juveniles were sighted on vegetation
in two locations. In Lucan, Co Dublin, two specimens
were collected in a public park, on webs built amongst
the branches at c. two meters high and less than ten
meters away from the parks’ outer boundary railings
which contained large numbers of adult specimens.
An additional four juveniles were observed in Oran-
more, Co Galway on the leaves of a large Hydrangea
contiguous to the glass wall of a heated swimming
pool located in the courtyard of a hotel complex.
PREDATION RECORDS
While sampling, several predation events were ob-
served, consisting of nine diet items and two preda-
tors of Steatoda nobilis. Diet items included a variety
of Irish native invertebrates belonging to three ar-
thropod subphyla. The subphylum Insecta was most
represented with six, comparatively medium to large
prey items, including a Coleopteran (Ocypus olens
Müller, 1764), a Dermapteran (Forfi cula auricularia
Linnaeus, 1758), a Hemipteran (Palomena prasina
Linnaeus, 1761), a Hymenopteran (Vespula vulgaris
Linnaeus, 1758) and two Dipterans, (Calliphora vom-
itoria Linnaeus, 1758 and a smaller non-identifi ed
specimen). Two additional prey items belonged to
the class Arachnida (subphylum Chelicerata) (Er-
atigena atrica Koch, 1843 and Araneus diadematus
Clerck, 1758). Woodlice ( subphylum Crustacea)
seem to be the commonest prey of all. In two in-
stances we recorded adult Steatoda nobilis falling
prey to common suburban spiders: the cellar spider
Pholcus phalangioides (Fuesslin, 1775) and the lace-
webbed spider Amaurobius fenestralis (Ström, 1768).
communally for the fi rst week after emerging from
the sac. They were then separated, kept individually in
1ml Eppendorf tubes and fed Drosophila melanogaster
(a stock of the wingless mutant for ease of handling)
twice weekly. The number of eggs or hatchlings for
each egg sac was recorded.
IDENTIFICATION CHART: PHOTOGRAPHY
AND CARAPACE MEASUREMENTS
Photographs of Steatoda nobilis were taken using
a Nikon AF-P DX NIKKOR 18–55mm f/3.5–
5.6G and a Nikon AF-S DX Micro Nikkor 40mm
f 2.8G lenses mounted on a Nikon D5200 DSLR
camera. Macro-photographs were taken using a
Sigma 105mm Macro lens mounted on a Canon
5DS camera. Pictures were manually adjusted for
light, contrast and colour using IrfanView 3.92
(1996–2004 Irfan Skijan; Vienna University of
Technology).
To investigate the mean size of individuals
within the Irish population of Steatoda nobilis, we
measured 102 mature specimens collected between
September 2015 and October 2016 in Co Dublin.
Specimens were placed in a gas chamber and ex-
posed to CO2 for two minutes until anaesthetised.
Spiders were then placed lying fl at on their ventral
aspect. Carapace length was measured using a preci-
sion analogue calliper and measurements rounded to
the closest 0.1mm. Carapace length was determined
by measuring each specimen from the proximal ar-
ticle of the chelicerae (in ‘normal’ resting position)
to the base of the spinnerets. Eggs and hatchlings
were measured with a ruler reticle mounted on an
Olympus SZ61 stereomicroscope.
RESULTS
COUNTY DISTRIBUTION OF STEATODA
NOBILIS
During the study that took place between Septem-
ber 2014 and February 2017, Steatoda nobilis was
identifi ed in 54 geographically distinct locations
across 16 Irish counties, of which a total of 15 are
new county records (Fig. 1). The social media-based
inquiries produced 36 of the new geographic loca-
tions (67%) across 13 counties, some dating back as
far as 2009 (Table 2). The remaining eighteen loca-
tions (33%) were registered by the authors between
2014 and 2016 across six counties (Table 1). As of 1
April 2017, our search on online wildlife recording
websites did not return any record for Ireland.
A total of 23 sighting locations (43%) were in
Co Dublin, where Steatoda nobilis was found in the
highest number and appears to be the most com-
mon species in and around street furniture. Thirty
of the 37 social media-based records were of a single
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THE FALSE WIDOW STEATODA NOBILIS IN IRELAND
83
Fig. 1—Occurrence of the Noble false widow Steatoda nobilis in Ireland. 36 positive reports across
13 counties were obtained from online social media. 32 additional locations across nine counties
were surveyed by the authors between September 2014 and February 2017. A total of 14 locations
in six counties yielded at least one specimen of Steatoda nobilis. The fi rst Irish sighting in Bray,
Co Wicklow (Nolan 1999) is marked by a star.
IDENTIFICATION CHART
Male and female Steatoda nobilis were photographed
at various stages of their development to help with
identifi cation. Steatoda nobilis displays a wide range
of variation in overall size, opisthosomal shape,
colouration and dorsal markings, making identifi -
cation very diffi cult to the untrained eye (Fig. 2).
Those variations do not seem to correlate with geo-
graphical origins or relatedness: specimens collected
centimetres apart and siblings born from the same
egg sac can display widely different dorsal patterns
(Figs. 3A–3D).
In Ireland, Steatoda nobilis can be consistently
distinguished from other local spiders (including
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BIOLOGY AND ENVIRONMENT
84
Table 2—Noble false widow spider Steatoda nobilis sightings in Ireland based on online reports
retrieved from two social media interest groups (facebook.com/groups/BritishSpiderIdentifi cation/;
facebook.com/groups/insectsinvertebratesire/). All reporters were contacted to obtain precise
location, details on habitat, dates of observation and photographic voucher material. Only reports
accompanied with unambiguous photographic material were retained. Coordinates were retrieved
from the National Biodiversity Data Centre, Waterford (http://maps.biodiversityireland.ie/#/Map).
Location Coordinates Habitats Observation dates
Co Dublin – Tyrellstown 307202, 241771 On a garden fence July 2009
Co Dublin – Balbriggan 320305, 263918 Outdoors - Garden wall October 2014
Co Dublin – Balbriggan 320371, 263938 Outdoors - On a fl ower pot September 2015
Co Dublin – Portmarnock 324224, 243176 Indoors September 2015
Co Dublin – Santry 316959, 240469 Outdoors - On stone pavement 2016
Co Dublin – Baldoyle 323986, 239991 Indoors - Window frame May 2016
Co Dublin - Glasnevin 314638, 237366 Outdoors - on garden wall May 2016
Co Dublin - Churchtown 315625, 228650 Indoors June 2016
Co Dublin - Skerries 324632, 259875 Indoors July 2016
Co Dublin - Coolock 319396, 239360 Outdoors August 2016
Co Dublin - Knocklyon 312220, 227546 Indoors - On wooden structure September 2016
Co Dublin - Shankill 324975, 221856 Outdoors - On a garden rock September 2016
Co Dublin - Sutton 325135, 239555 Outdoors - In garden September 2016
Co Dublin - Swords 319036, 246777 Outdoors - Garden wall October 2016
Co Donegal - Bundoran 182121, 358977 In arm pit of wet suit March 2016
Down – Bangor 350722, 378692 Indoors December 2016
Meath Kells 274762, 275309 Indoors - On a wall July 2014
Meath – Ratoath 302166, 251766 Indoors - Window frame October 2016
Kildare – Leixlip 300209, 235770 Outdoors November 2015
Laois – Clonkeen 243768, 196040 Indoors 2016
Wicklow – Hollywood /Donard 293708, 197630 Indoors on skirting board 2016
Wicklow – Greystones 328949, 212314 Indoors June 2016
Wicklow – Arklow 324208, 173379 Indoors October 2016
Wexford – Gorey 315525, 159179 Inside garden shed October 2010
Wexford – Wexford town 304477, 122145 Indoors November 2015
Wexford – Taghmon 291884, 119945 Indoors on a blanket September 2016
Wexford – Courttown 319446, 157427 Indoors - On window frame October 2016
Tipperary – Kilcash, Clonmel 231489, 128155 Indoors - On a wall July 2016
Waterford – Waterford City 262304, 110758 Indoors - On wooden fl oor September 2015
Waterford – Cherrymount 206328, 82579 Indoors March 2016
Waterford – Dungarvan 225932, 93016 Outdoors 2016
Carlow – Tullow 285544, 172950 Outdoors - on stone 2016
Kerry – Tralee 86865, 115194 Outdoors, on concrete February 2015
Cork – Cobh 178777, 67245 Indoors May 2015
Cork – Curraghbinny Woods 179281, 62036 Indoors - Window frame October 2016
Cork – Glanbeg 164119, 50847 Indoors 2016
other members from the genus Steatoda) by the pres-
ence of a cream crescent on the antero-lateral part
of the opisthosoma (Figs. 2B and 2E), an intricate
pentagonal or hexagonal cream-coloured pattern on
the dorsal aspect of the opisthosoma (Figs. 2A–2H)
and sturdy reddish to orange legs banded with black
markings (Figs. 2D and 3E). The prosoma is consis-
tently solid black in mature specimens but it may be
light yellow to cream colour in immature and freshly
moulted specimens (Fig. 2B). The cuticle of the
opisthosoma bears four small depressions on the dor-
sal aspect (Figs. 2D and 2F). Mature males are easily
distinguished from mature females due to the pres-
ence of a pair of palpal bulbs on the distal end of the
pedipalps (Figs. 2C, 2E and 2G). The size and shape of
the opisthosoma varies from short and slender (Figs.
2E and 2G) to large and bulbous (Fig. 2C). Old speci-
mens—particularly females—may present a small and
shrivelled opisthosoma with faded or absent dorsal
and antero-dorsal markings (Figs. 2G, 2H).
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THE FALSE WIDOW STEATODA NOBILIS IN IRELAND
85
Fig. 2—Identifi cation chart for various life stages of Steatoda nobilis collected in Ireland. Variations
in opisthosoma markings are presented in each frame. (A) Unsexed second instar juvenile
specimen; (B) Unsexed sub-adult specimen hours after ecdysis. Notice the pale colour of the
prosoma and legs in contrast to other specimens. (C) Male specimen at the penultimate
developmental stage; (D) Mature female with reduced opisthosomal markings; (E) Mature male
displaying mature palpal bulbs on the distal end of the pedipalps; (F) Large mature female with
round, bulbous abdomen and reduced opisthosomal markings; (G) Mature male with slender,
discoloured opisthosoma and mature palpal bulbs on the distal end of the pedipalps; (H) Old
mature female, with a missing frontal leg, slender, shrivelled abdomen. The opisthosomal
markings are barely visible.
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BIOLOGY AND ENVIRONMENT
86
the egg sac resembles a spherical or pear-shaped
mass 5–12mm in diameter, suspended by threads
inside the brooding chamber (Fig. 4). After an av-
erage of 18 days at 20°C, spiderlings emerge from
their chorion, and remain within the egg sac, where
The average body length (prosoma +
opisthosoma) was 10.5mm for mature females
(N=90) and 9.4 mm for mature males (N=12).
The largest mature female measured 13.7mm and
the largest mature male measured 11.6mm. When
hatching, juveniles measure 1.7mm (N=15) and the
sexes are indistinguishable from each other.
REPRODUCTIVE RATE
For the present study, females and males were housed
separately in the lab; over a period of 11 months, 40
wild-caught females produced a total of 50 egg sacs
in captivity. Each egg sac contained on average 94
eggs (range 34 to 208 eggs). The most prolifi c spider
produced four egg sacs within four months.
Prior to oviposition, the female produces an
irregular silky brooding chamber approximately
3–4cm in diameter which does not possess any en-
trance. After two to ten days spent in the brood-
ing chamber, a spherical or pear-shaped egg sac
is produced. Eggs are laid in quick succession and
clumped together into a spherical mass. A fi rst layer
of loose silk is produced around the egg mass, fol-
lowed by a second layer of denser silk. Ultimately,
Fig. 3—(A–D) Sibling second instar Steatoda nobilis hatched from the same egg sack. Note the
wide variations in the intensity and shape of the opisthosomal markings. (E) Mature female S.
nobilis with four prominent dimples on the dorsal aspect of the opisthosoma, characteristic of
the genus Steatoda. Note the reduced dorsal markings but the presence of a cream band on the
antero-lateral aspect of the opisthosoma.
Fig. 4—Captive mature female Steatoda nobilis
guarding her egg sac suspended in a brooding
chamber made for that purpose. The egg mass
is visible through the silk as the faint yellow
circular shape at the centre of the egg sac.
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THE FALSE WIDOW STEATODA NOBILIS IN IRELAND
87
they undergo a fi rst ecdysis. Two to four days after
the fi rst moult, spiderlings emerge from the egg
sac and collectively produce a long clump of silk
threads along which they settle as a group. At this
stage, the spiderlings are capable of capturing and
consuming small live prey (e.g. Drosophila melano-
gaster). Dispersal occurs several days later, at which
point the spiderlings display increasing cannibalistic
behaviour against their siblings.
DISCUSSION
IRISH DISTRIBUTION
Considering its conspicuous dorsal markings, over-
all body size and synanthropic affi nities, it is unlikely
(but not impossible) that Irish populations of Ste-
atoda nobilis passed unnoticed for several years prior
to Nolan’s report (1999). Van Helsdingen (1996),
did not include the species in his extensive literature
review on Irish spiders. Rapid colonisation event by
Steatoda nobilis has been reported before from Cal-
ifornia, where the species has become widespread
within three years of the fi rst sighting (Vetter and
Rust 2012; Vetter et al. 2015).
Although we did not survey each of the 32
Irish counties, the present study shows that since
Nolan’s report (1999), Steatoda nobilis has expanded
its range that now includes at least sixteen counties.
Within the last two decades, Steatoda nobilis has es-
tablished thriving colonies in major port towns on
the eastern, southern and western coasts of Ireland
and, to a lesser extent, in the midland counties. Most
sightings recorded during the course of this study
occurred in cities or along major transport routes
across Ireland, with the exception of a single spec-
imen captured in a bungalow located in Curragh-
binny Woods, near the coastal village of Crosshaven,
Co Cork. Surveys of coastal habitats, meadows and
woodlands in Cos Galway, Mayo and Roscommon
did not yield any additional specimen. There is no
doubt however that a comprehensive, nationwide
survey would yield many more additional positive
records.
The evident distribution pattern that emerges
from our survey is the distinct preference of Steatoda
nobilis for man-made structures: all sightings were
made in and around houses or on street furniture.
This is in contrast to its native range where Steatoda
nobilis occupy mixed habitats consisting of natural
features (e.g. plants and rock crevices) and man-
made structures. In Italy, Steatoda nobilis occurred
fi rst in urban areas and then spread to the surround-
ing countryside (Kulczycki et al., 2012) while in
the northern part of its new range, Steatoda nobilis
appears to be restricted to man-made habitats. This
pattern suggests a climate-dependent colonisation:
Steatoda nobilis is an exclusively synanthropic species
in Ireland, and its current long-range expansion is
highly dependent on human activity rather than
natural dispersal methods such as ballooning. Un-
intentional human-led introductions are believed
to have been the main factor in the introduction
of over 87 species of non-native spiders in Europe
between 1850 and 2000, of which 71% live synan-
thropically (Kobelt and Nentwig 2008).
INTRAGUILD COMPETITION, REPRODUCTIVE
RATE AND POTENTIAL IMPACT
The impact of alien spiders on native Irish ecosys-
tems has not been investigated yet but some ob-
servations can be drawn from our dataset. Steatoda
nobilis appears to be a generalist feeder, preying on a
wide range of arthropods, as long as the prey can be
immobilised and consumed. The few interactions
between Steatoda nobilis and native (or naturalised)
spiders recorded here show that large numbers of
Steatoda nobilis might have a negative impact on
local populations of common urban dwellers such
as the missing sector orb weaver Zygiella x-notata.
This species occurs in habitats which are also fa-
voured by Steatoda nobilis (e.g. street furniture, rail-
ings and stone walls) and competition between both
species is therefore likely. Although Zygiella x-notata
and Steatoda nobilis have been observed side by side
during our site inspections, it seems that Zygiella x-
notata is not as widespread in those areas colonised
by Steatoda nobilis than in locations where we did
not observe the presence of Steatoda nobilis. Inter-
specifi c competition for prey items is a possible fac-
tor for this observation, as it has been shown that
prey availability is a major factor for the successful
establishment or the displacement of Zygiella x-no-
tata colonies (Wherry and Elwood 2009).
Differences in reproductive rates may bring
additional stress on local species that are unable to
compete with the larger, more productive Steatoda
nobilis. Zygiella x-notata has been shown to pro-
duce one–three egg sacs per year, each containing
c.10–70 eggs (Wherry and Elwood 2009). In com-
parison, our data shows that Steatoda nobilis can pro-
duce much larger egg sacs containing between 34
and 208 eggs (98 eggs in average per clutch), every
month, over a period of several months. Previous
reports show that Steatoda nobilis can still produce
viable clutches 18 months following fertilisation
(Locket 1979). Additionally, Zygiella x- notata does
not lay eggs during the coldest month of the year
(Wherry and Elwood 2009) while female Steatoda
nobilis are cold tolerant (Jones 1979) and active
throughout the year. In our study, Steatoda nobilis
captured outdoors in the middle of winter were
capable of producing viable egg sacs days only after
being established in the lab. In addition, Steatoda
nobilis has a remarkable life span: a specimen kept
in a sheltered environment free of predators can
live over fi ve and a half years (Snazell 1993) against
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BIOLOGY AND ENVIRONMENT
88
twelve months on average for Zygiella x-notata
(Yoward 1999). Considering the preference of Ste-
atoda nobilis for sheltered habitats where it has few
to no predators, it is likely that ‘wild’ specimens are
almost as productive and long-lived as the speci-
mens kept in captivity. If this is the case, Steatoda
nobilis may well have the potential to outcompete
native urban dwelling spiders. Further fi eld-based
studies and long-term surveys will be needed to
monitor the range expansion of Steatoda nobilis
and to assess if this occurs at the expense of native
species.
ACKNOWLEDGEMENTS
The authors would like to thank P and J Dun-
bar, Emma Lawlor, Dylan O Moore, Nicholas
Irani, James Dunbar, Eoin MacLoughlin and Craig
Curry for assistance dur ing fi eld work; Milca Gabb
and Andy Wilson (MIAN Photography and Train-
ing) for their help with photography; Dr Margaret
Flaherty for her assistance with GIS data and Prof
Wallace Arthur for kindly reviewing this man-
uscript before submission. This work has been
fi nanced through an Irish Research Council post-
doctoral fellowship held by Michel Dugon and a
NUI Galway College of Science PhD scholarship
held by John Dunbar.
REFERENCES
Bate, R. (2005). Steatoda nobilis in Warwickshire. Spider
Recording Scheme 80, 15. Newsletter of the British
Arachnological Society, 131.
Binding, A. (2014). Steatoda nobilis, the fi rst record from
Lincolnshire. Spider Recording Scheme 41, 8. News-
letter of the British Arachnological Society.
Bristowe, W.S. (1929). The Distribution and Dispersal of
Spiders. Proceedings of the Zoological Society of London,
99, 633–657.
Cardoso, P. (2000). Portuguese spiders (Araneae): a pre-
liminary checklist. Ekológia (Bratislava), 19, 19–29.
Daws, J. (2008). Steatoda nobilis in Leicestershire. Spider
Recording Scheme 62, 18. Newsletter of the British
Arachnological Society, 113, 18.
Déjean, S. (2013). Quelques observations d’araignées
(Arachnida, Araneae) dans les provinces de Castillon
et de Valence (Espagne). Revista Ibérica de Aracnología,
23, 133–140.
Faúndez, E.I. and Téllez, F. (2016). Primer registro de
una mordedura de Steatoda nobilis (Thorell, 1875)
(Arachnida: Araneae: Theridiidae) en Chile. Arquivos
Entomolóxicos, 15, 237–240.
Hann, S.W. (1990). Evidence for the displacement of an
endemic New Zealand spider, Latrodectus katipo
Powell by the South Afr ican species Steatoda
capensis Hann (Araneae: Theridiidae). New Zealand
Journal of Zoology, 17, 295–307.
Jackson, A.R. (1907). On some rare arachnids captured
during 1906. Report and Proceedings of the Chester So-
ciety of Natural Science, 6, 1–8.
Jones, D. (1979). Steatoda nobilis (Thorell) 1875, its occa-
sional appearance in Britain. Newsletter of the British
Arachnological Society, 24, 3–5.
Jones, D. (1987). The return of Steatoda nobilis (Thorell).
Newsletter of the British Arachnological Society, 49, 7–8.
Jones, G. (2006). Steatoda nobilis (Thorell 1875) a spider
new to Wales at Barry, Glamorgan (VC41). Spider
Recording Scheme 55, 20. Newsletter of the British
Arachnological Society.
Kobelt, M. and Nentwig, W. (2008). Alien spider intro-
ductions to Europe supported by global trade. Journal
of Diversity and Distribution, 14, 273–280.
Kovoor J. and Muñoz-Cuevas A. (2000). Diversité des
Arachnides dans les îles d’Hyères (Porquerolles et
Port-Cros, Var, France). Modifi cations au cours du
XXe siècle. Zoosystema, 22, 33–69.
Kulczycki, A., Simeon, E., Legittimo, C.M. and Di
Pompeo, P. (2012). New Records of Steatoda no-
bilis (Thorell, 1875) (Araneae, Theridiidae), an in-
troduced species on the Italian mainland and in
Sardinia. Arachnology, 15, 269–272.
Locket, G. H. (1979). Some notes on the life history of
Steatoda nobilis (Thorell). Newsletter of the British
Arachnological Society, 25, 8.
Merrett, P. (1989). Twelve hundred new county records
of British spiders. Bulletin of the British Arachnological
Society, 8, 1–4.
Nolan, M. (1999). Three spiders (Araneae) new to Ire-
land: Bolyphantes alticeps, Oonops domesticus and
Steatoda nobilis. The Irish Naturalists’ Journal, 26,
200–202.
Pickard-Cambridge, O. (1879). On some new and rare
British spiders, with characters of a new genus. An-
nals and Magazine of Natural History, 5, 190–215.
Reiser, N. (2013). Einschleppung und Einwanderung von
Spinnentieren (Araneae; Opiliones) in Deutschland.
Bachelorarbeit zur Erlangung des akademischen
GradeSteatoda Hochschule Neubrandenburg Fach-
bereich Landschaftswissenschaften und Geomatik
Naturschutz und Landnutzungsplanung.
Smith, C. J. (1992). Steatoda nobilis Spider Recording
Scheme 15, 7. Newsletter of the British Arachnological
Society.
Snazell, R. and Jones, D. (1993). The theridiid spider Ste-
atoda nobilis (Thorell, 1875) in Br itain. Bulletin of the
Bitish arachnological Society, 9, 164–167.
Taucare-Ríos, A., Mardones, D., Zúñiga-Reinoso, A.
(2016). Steatoda nobilis (Araneae: Theridiidae) in
South America: a new alien species for Chile. The
Canadian Entomologist, 148, 479–481.
Thorell, T. (1875). Diagnoses Aranearum Europaearum
aliquot novarum. Tijdschrift voor Entomologie, 18,
81–108.
Turkey, T. and Mergen, O. (2007). The comb-footed spider
fauna of the central Anatolia region and new records
for the Turkish fauna (Araneae: Theridiidae). Serket,
10, 112–119.
Van Helsdingen, P. J. (1996). The county distribution of
Irish spiders, incorporating a revised catalogue of the
species. The Irish Naturalists’ Journal, 25: 1–87, 89-92.
This content downloaded from 140.203.255.58 on Mon, 18 Sep 2017 20:22:59 UTC
All use subject to http://about.jstor.org/terms
THE FALSE WIDOW STEATODA NOBILIS IN IRELAND
89
Van Keer, K. (2010). An update on the verifi ed reports of
imported spiders (Araneae) from Belgium. Nieuwsbrief
van de Belgische Arachnologische Vereniging, 25, 210–214.
Vetter, R.S. and M.K. Rust. (2012). A large European comb-
foot spider, Steatoda nobilis (Thorell, 1875) (Araneae:
Theridiidae) newly established in Ventura County, Cal-
ifornia. The Pan-Pacifi c Entomologist, 88, 92–97.
Vetter, R.S., Adams, R.J., Berrian, J.E. and Vincent,
L.S. (2015). The European spider Steatoda nobilis
(Thorell, 1875) (Araneae: Theridiidae) becoming
widespread in California. The Pan-Pacifi c Entomolo-
gist, 91, 98–100.
Warrell, D.A., Shaheen, J., Hillyard, P.D. and Jones, D.
(1991). Neurotoxic envenoming by an immigrant
spider (Steatoda nobilis) in southern England.
Toxicon, 29, 1263–1265.
Wherry, T. and Elwood, R.W. (2009). Relocation, repro-
duction and remaining alive in an orb-web spider.
Journal of Zoology, 279, 57–63.
Yoward, P. (1999). Sedentary monogamy and geri-
atric persistence of existence in the spider Zy-
giella x-notata (Clerck, 1757). Spider Recording
Scheme 84, 6. Newsletter of the British Arachnological
Society.
Zamani, A., Mirshamsi, O., Jannesar, B., Marusik, Y.M.
and Esyunin, S.L. (2015). New data on spider fauna
of Iran (Arachnida: Araneae), Part II. Zoology and
Ecology, 25, 339–346.
This content downloaded from 140.203.255.58 on Mon, 18 Sep 2017 20:22:59 UTC
All use subject to http://about.jstor.org/terms
