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A history of accidental widow spider (genus Latrodectus )
introductions on the island of Ireland with a new irish
record for Latrodectus hesperus (Chamberlin and Ivie, 1935),
and additional records of Latrodectus geometricus (C.L.
Koch, 1841).
B.L. Collier, M.M. Dugon, M. Nolan, A. Fort, K. Healy, A. Vitkauskaite, K.
Lyons, E.J. Munnelly, L. McSharry, J.P. Dunbar
Biology and Environment: Proceedings of the Royal Irish Academy,
Volume 123B, Number 3, 2023, pp. 111-120 (Article)
Published by Royal Irish Academy
DOI:
For additional information about this article
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https://doi.org/10.1353/bae.2023.a915306
https://muse.jhu.edu/article/915306 Creative Commons Attribution 4.0 International License.
Received 26 May 2023.
Accepted 9 October 2023.
Published 24 November 2023
B.L. Collier
(corresponding author;
email: b.collier2@
universityofgalway.
ie. ORCID iD: https://
orcid.org/0000-0002-
0709-9678), Ryan
Institute, University
of Galway; M.M.
Dugon, Ryan Institute,
University of Galway;
M. Nolan, Natural
History, National
Museum of Ireland;
A. Fort, Department
of Pharmaceutical
Sciences and
Biotechnology,
Technological University
of the Shannon:
Midlands Midwest; K.
Healy, A. Vitkauskaite,
K. Lyons, E.J. Munnelly,
L. McSharry and J.P.
Dunbar, Ryan Institute,
University of Galway.
Cite as follows: Collier,
B.L., Dugon, M.M.,
Nolan, M., Fort, A.,
Healy, K., Vitkauskaite,
A., Lyons, K., Munnelly,
E.J., McSharry, L. and
Dunbar, J.P. 2023 A
history of accidental
widow spider
(genus Latrodectus)
introductions on the
island of Ireland with
a new irish record for
Latrodectus hesperus
(Chamberlin and Ivie,
1935), and additional
records of Latrodectus
geometricus (C.L.
Koch, 1841). Biology
and Environment:
Proceedings of the
Royal Irish Academy
123B (3).
111
Biology and EnvironmEnt: ProcEEdings of t hE royal irish ac adE my, vol . 123B, no. 3, 111–120 (2023). © thE authors
this is a n OPEn AccEss Articl E und Er t hE t Erm s of t hE crEati vE commons attriBution licEns E, which PErmits usE, distriBution
and rEProduction in any mEdi um, Provi dEd t hE original wor k is ProPE rly cit Ed. oP En acc Ess funding P rovidE d By irEl.
A HISTORY OF ACCIDENTAL WIDOW
SPIDER (GENUS LATRODECTUS)
INTRODUCTIONS ON THE ISLAND
OF IRELAND WITH A NEW IRISH
RECORD FOR LATRODECTUS HESPERUS
(CHAMBERLIN AND IVIE, 1935), AND
ADDITIONAL RECORDS OF LATRODECTUS
GEOMETRICUS (C.L. KOCH, 1841)
B.L. Collier, M.M. Dugon, M. Nolan, A. Fort, K. Healy, A. Vitkauskaite,
K. Lyons, E.J. Munnelly, L. McSharry and J.P. Dunbar
ABSTRACT
The widow spiders of the genus Latrodectus (Araneae: Theridiidae) have a well-documented global
medical significance due to the potent venom many of them possess. This medical importance par-
tially stems from the global range expansion the genus has undergone, facilitated in part by human
trade. This expansion has had an impact on human health in countries where Latrodectus spiders
establish populations. Ireland has a detailed report history of accidental widow spider introductions,
spanning over 30 years, which assists in understanding the potential such species have for establish-
ing. Here we present three additional cases: a second and third record of Latrodectus geometricus (C.L.
Koch, 1841) and the first record of Latrodectus hesperus (Chamberlin and Ivie, 1935). We also review
all published reports of Latrodectus introductions in Ireland and discuss the potential for populations to
establish. While case histories suggest that L. hesperus and L. geometricus can survive Irish winters, it is
not certain that they can complete an egg-to-egg life cycle or even reproduce. Nevertheless, it seems
possible they could do so in favourable micro-habitats in anthropogenic habitats such as hot houses.
Identification of instances of Latrodectus introductions into Ireland is essential to prevent potential
establishments that could lead to envenoming cases.
INTRODUCTION
In Ireland and Britain, there are 19 genera of comb-
footed spiders (Araneae: Theridiidae) encompassing
58 native and non-native species (Bee et al. 2020).
Of the identified non-native species, those from
the subfamily Latrodectinae (Petrunkevitch, 1928)
known as ‘false’ widows (genus Steatoda Sundevall,
1833) are closely related to the highly potent ‘true’
widows (genus Latrodectus Walckenaer, 1805) (Daly
et al. 2001), and are also of known medical signif-
icance (Dunbar et al. 2018a; Dunbar et al. 2020;
Dunbar et al. 2022b; Isbister and Gray 2003; Kham-
torn et al. 2022). In Ireland, four species of Steatoda
have been recorded: Steatoda nobilis (Thorell, 1875),
Steatoda grossa (C.L. Koch, 1838), Steatoda bipunctata
(L.) and Steatoda triangulosa (Walckenaer, 1802). Of
these species, S. grossa has the widest range, occur-
ring in at least eleven counties, while S. bipunctata is
only known from two counties and S. triangulosa is
limited to a single imported specimen, having not
yet established on the island of Ireland (Dunbar et al.
2018b). While S. grossa and S. bipunctata have been
present in Ireland’s synanthropic habitats for over a
century, their ranges and population densities differ
significantly to that of S. nobilis, which has estab-
lished dense populations across the island since its
discovery in 1998 (Nolan 1999). Similarly, several of
the 34 species in the closely related genus Latrodec-
tus have a history of establishing populations outside
of their native range (World Spider Catalog 2023),
and two species with significant invasive impact on
human health and native species; Latrodectus geo-
metricus, prevalent in Austral Africa, and Latrodectus
Bio lo g y An d En v i ro n m E nt
112
remnants of a dead spider in a punnet of grapes he
had purchased at a Dublin retail outlet within the
previous few days. He forwarded the remnants to
MN, and they were found to be squashed and some-
what desiccated. The epigyne and internal genital
structures were, however, entirely intact, and it was
possible to identify the specimen as Latrodectus geo-
metricus (Levi 1959) by comparing it with a speci-
men that had previously turned up in Ireland (Nolan
2012). The genitalia of this species are quite distinct,
and the two specimens matched very closely. The
grapes had originated from Peru.
Case 5.
Latrodectus geometricus – Co. Derry
On 18 February 2018, a spider was discovered in
a punnet of grapes by A. Campbell in Co. Derry
after purchasing it from a local supermarket. The
spider was alive but was accidentally killed after it
ran out of the container (Fig. 1A). Upon further
inspection, an unopened egg sac was found to be
attached to the grapes (Fig. 1B). The remains of
the spider and the egg sac were sent to the au-
thors and were identified as Latrodectus geometricus
by the form of the sac and by DNA analysis (see
below). This punnet of grapes had also originated
from Peru.
Case 6
Latrodectus hesperus – Co. Meath
On 17 October 2019, one of the authors, JPD, was
contacted by a commercial food truck restoration
company based in Piercetown, Co. Meath and
asked to identify two spiders found in a vintage
hasseltii (Thorell, 1870), widespread in Australia, have
extended their range in the Northern and Southern
hemispheres (Taucare-Ríos et al. 2016; Vetter et al.
2012; Vink et al. 2011). For example, L. hasseltii has
established large populations in Japan (Luo et al.
2022), which have created a novel public health
crisis due to human envenomings and the need
for antivenom (Hifumi et al. 2016; Kobayashi et al.
1998). Additionally, L. geometricus populations shown
targeted aggression and displacive potential toward
other Latrodectus species in the Southern United
States (Coticchio et al. 2023; Vetter et al. 2012).
In Ireland, two species of Latrodectus (Latrodec-
tus mactans (Fabricius) and L. geometricus) have been
previously reported (Nolan 2012; O’Connor and
Holmes 1993; Ross 1988), discussed chronologically
here as Cases 1–3. We present three new cases (4–6
chronologically) of accidental introductions of La-
trodectus into Ireland and review published cases of
Latrodectus introductions into Ireland. While there is
no evidence of established populations on the is-
land of Ireland, we discuss the potential for Latrodec-
tus species to become established here and possible
medical implications.
CASE PRESENTATIONS
THREE NEW CASES OF LATRODECTUS SP.
INTRODUCTION IN IRELAND
Case 4.
Latrodectus geometricus – Co. Dublin
On 5 January 2015, one of the authors, MN, was
contacted by D. O’Donnell who had noticed the
Fig. 1—A specimen of Latrodectus geometricus discovered in Co. Derry (February 2018). (A) the
remains of the spider and (B) the egg sac attached to the grapes in the package it arrived in.
A h is t ory o f A cc i de n tA l Lat ro d ec t u s in t ro d uc t io ns
113
malnourished and dehydrated (Fig. 3A). The spider
was successfully captured on site, and then housed
by J.P.D. (Fig. 3B, 3C, 3D).
SUMMARY OF PREVIOUS CASES OF
LATRODECTUS RECORDED IN IRELAND
Case 1
The first noted observation of Latrodectus on the
island of Ireland was made in 1988 (Ross 1988).
It was documented that a live black spider was
discovered amongst a consignment of Southern
Californian grapes in a shopping centre in Bally-
mena, Co. Antrim. This live specimen was sent to
the Zoology Research Division, Belfast where it
was identified as an ‘adult female American black
widow spider’ L. mactans. Mr J. Devlin, who spotted
the spider, had been aware of reports of live spec-
imens of black widows turning up in grape con-
signments in several places in England (Ross 1988),
so he thought to report the specimen. Ross notes
that the British Museum had acquired several of
the specimens and reports, also, that it had recently
received a specimen of Steatoda (Theotoda in the
text) which had been recently imported from the
eastern Mediterranean in similar grape consign-
ments (Ross 1988). While Southern California is
outside the typical range of L. mactans (Schraft et
al. 2021), the species has a well-documented po-
tential for expansion throughout the United States,
including the temperate West Coast (Deevey 1949;
Mote and Gray 1935), and could survive in the
warmer climate of Southern California (Sadir and
Marske 2021).
van imported from California to Ireland in January
2019. Restoration work began nine months after
it had arrived in Ireland, and a black spider (Fig.
2B) was discovered on the engine. The spider was
accidentally injured and died shortly after. Further
inspection revealed another spider within a web
on the door panel (Fig. 2A, Supplementary Data,
Video 1), which retreated when disturbed and
could not be found in a subsequent search. Both
spiders were similar in size and appearance, and
each had a red hourglass marking on the ventral
surface of the opisthosoma (Fig. 2A, 2C). The re-
mains of the deceased specimen were collected by
the authors and identified as L. hesperus by DNA
analysis (see below). Juvenile specimens of Steatoda
nobilis were also discovered in the van, and while
the species is established in Ireland, they too might
have originated from California where the species
has also established itself (Vetter et al. 2015; Vetter
and Rust 2012). Within the van and nearby where
the L. hesperus specimen was found, the remains
of a giant house spider, Eratigena sp. (C.L. Koch,
1843), were discovered wrapped in silk within a
web (Supplementary Data, Video 2). It is not cer-
tain which species present in the van captured and
wrapped the E. atrica specimen, but the proximity
to L. hesperus could indicate it as a possible prey
item prior to discovery. Subsequently, work on the
van halted and it was left parked on the property
for another year.
On 23 October 2020, after work commenced
on the van yet again, a spider matching the descrip-
tion of the previous spiders discovered a year prior
was found on the door panel of the same van (Fig. 3).
The specimen was alive but appeared to be slightly
Fig. 2—Two specimens of Latrodectus hesperus discovered in the vintage van in Co. Meath (October
2019). (A) The specimen on the door panel that evaded capture, and (B,C) the captured specimen
that later died.
Bio lo g y An d En v i ro n m E nt
114
Case 2
This record is from 1992 in Walkinstown, Co. Dub-
lin when a spider resembling that of a black widow
was found in a consignment of empty beer contain-
ers imported from North America (O’Connor and
Holmes 1993). The specimen was alive on discovery
but was deemed to be in a ‘not active’ state; its legs
were observed twitching before it eventually died.
The remains of the spider were sent to the National
Museum of Ireland in Dublin and was identified as
Latrodectus mactans by Dr James O’Connor (O’Con-
nor and Holmes 1993). The specimen was retained
in the national collection NH:1992.8.1.
Although the specimens presented in Ross
(1988) and O’Connor and Holmes (1993) were iden-
tified as Latrodectus mactans (Table 1), it is unclear if
these identifications were correct as female L. mactans
and Latrodectus hesperus cannot be clearly differentiated
by morphological characteristics that separate females
of other Latrodectus species (Cabrera-Espinosa and
Valdez-Mondragón 2021). Because the ranges of L.
hesperus and L. mactans may (but do not usually) over-
lap in parts of Southern California (Sadir and Marske
2021), it is possible that either species could have been
involved in the records designated L. mactans by Ross
(1988) and O’Connor and Holmes (1993).
The female was re-examined by MN, the epi-
gyne photographed and the internal genitalia cleared
to reveal the form of the copulatory ducts. These ad-
nexae showed the typical v-form of the paired sper-
mathecae and four loops to the copulatory ducts on
each side (Fig. 4). Cabrera-Espinosa and Valdez-Mon-
dragón (2021), however, note that different authors
ascribe differing numbers of ducts to L. mactans and
L. hesperus, and that in Mexican populations both can
have four loops to. Thus, this feature does not resolve
the question of the species involved.
Case 3
In 2011 several live spiderlings and a dead adult spider
were found in a utility room at a national school in
Abbeyfeale, Co. Limerick (Nolan 2012). The speci-
mens had emerged from a wooden musical instrument
(balafon) imported from Zambia two months prior.
The deceased adult specimen was sent to the National
Biodiversity Data Centre in Waterford whence it was
forwarded to MN who identified it as a Latrodectus spe-
cies. It was not until later in the year however, when
MN was sent the balafon and examined it, that it was
possible to identify the specimen with certainty as L.
geometricus on basis of three distinctive egg sacs within
Fig. 3—A specimen of Latrodectus hesperus discovered in a van the following year (October 2020).
(A,B) Specimen was captured and (C,D) housed by JPD.
A h is t ory o f A cc i de n tA l Lat ro d ec t u s in t ro d uc t io ns
115
up to two years post-copulation and can produce large
amounts of fertilised eggs on a regular basis when in
suitable environmental conditions (Douglas et al. 2014;
Mowery et al. 2022; Waner et al. 2018).
DISCUSSION
THE POTENTIAL FOR LATRODECTUS TO
BECOME ESTABLISHED ON THE ISLAND OF
IRELAND
Adaptive traits
The rise in global trade over the last century has
facilitated a significant rise in non-native spider
one of the gourds. L. geometricus is suspected to be na-
tive to Zambia (Garb et al. 2004; Sadir and Marske
2021; Taucare-Ríos et al. 2016).
Nolan (2012) noted that spiderlings had emerged
from one sac, that a second contained post- larval
hatchlings, and a third had undeveloped eggs. If ju-
venile stage and egg development can be taken as an
index of when sacs were produced, then the sac from
which spiderlings emerged can be supposed to have
been the first produced and that with undeveloped
eggs the last. This could imply that the undeveloped
sac, at very least, was set in Ireland. However, this can-
not be stated with certainty since exact dates for the
import of the balafon and the emergence of the spid-
erlings are not available. Previous studies have indicated
that Latrodectus geometricus females can retain sperm for
Fig. 4—Epigyne and adnexae of the Case 2 Walkinstown Latrodectus specimen (identified as
L. mactans) (NMI:1992.8.1). (A) The typical epigynal opening with a small, raised point medially
on the anterior margin and the (now yellowed) ‘hourglass’ shape on the ventrum. (B) The
v-form paired spermathecae and four loops to the copulatory ducts on each side (arrowed). All
these features can be characteristic of both L. mactans and L. hesperus.
Table 1—Records of all novel and published Latrodectus introductions into Ireland. Previously
published records (Nolan 2012; O’Connor and Holmes 1993; Ross 1988) have been marked with
an asterisk (*).
Species Location Date of import Date(s) of discovery Specimens
L. mactans Co. Antrim –
Shopping Centre 10-12 July 1988 14 July 1988 1 adult female
L. mactans Co. Dublin
– Walkinstown N/A 20 January 1992 1 adult female
L. geometricus Co. Limerick –
National School January 2011 March 2011 1 adult female, 3
egg sacs, multiple
hatchlings from one sac
L. geometricus Co. Dublin –
Retail Store December 2014 –
January 2015 <c.5 January 2015 1 adult female
L. geometricus Co. Derry –
Convenience Store N/A 18 February 2018 1 adult female, 1
egg sac
L. hesperus Co. Meath – Food
Truck Restoration January 2019 17 October 2019
23 October 2020 2 adult females
Bio lo g y An d En v i ro n m E nt
116
colonisations (Kobelt and Nentwig 2008; Nentwig
2015). Despite being imported at least twice, there is
currently no evidence of long-term survivorship by
North American black widows the island (O’Con-
nor and Holmes 1993; Ross 1988). Based on the
records presented in Case 6, however, L. hesperus can
survive in sheltered man-made structures in Ireland
for extended periods (20 months). This also suggests
that the specimens living in the van survived two
Irish winter cycles. The survival of these L. hesperus
specimens for 20 months outside of their usual cli-
mate range, and through two winter cycles, might
suggest they spent much of the time in low-meta-
bolic diapause. Their condition suggested starvation
and dehydration. While they are generalist preda-
tors, which is advantageous (Salomon 2011), some
Latrodectus species are known to be able to fast for
long periods, e.g. L. hasseltii can survive up to three
months without food (Forster and Kavale 1989). In
contrast to the L. geometricus report in Case 3 (Nolan
2012), no egg sacs or spiderlings were found over
the course of the investigation. Therefore, it cannot
be inferred that L. hesperus is capable of breeding or
producing viable offspring in the Irish climate. How-
ever, it is possible that the spiders were juvenile spec-
imens when they left the USA and matured during
their transit or after arriving in Ireland. Moreover,
two of L. hesperus’ close relatives, L. geometricus and L.
hasseltii, can retain sperm from previous fertilisation
events between late-subadult and adult development
stages; although the length of time that the sperm
can be retained is currently unknown (Baruffaldi
and Andrade 2017; Sentenská et al. 2021).
The Case 3 record of L. geometricus (Nolan
2012) suggests a relatively short post-import sur-
vival period, but it might be asked whether the
species could survive on the island for longer du-
rations. L. geometricus has a long and well-docu-
mented history of establishing populations outside
of its native Austral African range (Lotz 1994). For
example, populations have been described in parts
of the Middle East (Levy and Amitai 1983; Türkeş
and Mergen 2005), Southeast Asia (Muslimin et
al. 2015; Shukla and Broome 2007), Japan (Ono
1995), Australia (Forster and Forster 1999), French
Polynesia (Marie and Vetter 2015), South America
(Almeida et al. 2009; Simó et al. 2013; Taucare-Ríos
and Canals 2015), the southern continental United
States (Garb et al. 2004; Sadir and Marske 2021;
Schraft et al. 2021; Vetter et al. 2012), and Hawaii
(Pinter 1980). All these regions have much warmer
and drier climates than Ireland. Also, in the cases
of the accidental import of L. geometricus into both
Poland (Rozwałka 2017) and the Netherlands
(Noordijk 2016), specimens failed to disperse from
the vessels they were transported in or to establish.
This possibly indicates that the species is unable to
survive in the milder outdoor climate of northern
European countries, including Ireland.
It is therefore unlikely that L. geometricus would
become established in Ireland other than in an en-
vironment that strongly emulated, all year round,
the warmer climate the spider probably needs, e.g.,
a botanical hot-house or biodome. We are not aware
that any Latrodectus species has colonised such envi-
ronments anywhere in Europe. The only Latrodectus
species native to a wide area of Europe, L. tredecim-
guttatus, does not seem to be transported with any
regularity within Europe (i.e. there is no indication
of this in an online database of European spiders
(Nentwig et al. 2023)). This is probably related to
its preference for non-synanthropic habitats where it
sets a web close to the ground, making it less amena-
ble to transportation by human agents (Mora-Rubio
and Parejo-Pulido 2021). Because of their differing
habitat preferences, it seems unlikely that a popula-
tion of L. geometricus that was established within the
endemic range of L. tredecimguttatus could put that
species at risk of displacement.
It is notable that all the Latrodectus specimens
recorded in Ireland were female and two of these
produced egg sacs; the ability to reproduce being an
obvious prerequisite to colonisation.
Potential implications
The genus Latrodectus contains several species of
medical importance (Almeida et al. 2009; Clark et
al. 1992; Garb et al. 2004; Khamtorn et al. 2022).
With the introduction of Latrodectus species to new
environments comes the novel risk of human en-
venoming. Currently, the only medically significant
spider species in Ireland is Steatoda nobilis (Dunbar
et al. 2018a; Dunbar et al. 2022b). S. nobilis shares
over 60% of its venom repertoire with Latrodectus
and envenoming by S. nobilis and S. grossa can pres-
ent latrodectism-like symptoms (Dunbar et al. 2020;
Graudins et al. 2002). Latrodectus geometricus shares
more of its venom components with S. nobilis than
L. hesperus (Khamtorn et al. 2022). To date, there have
been no human deaths resulting from envenoming
by S. nobilis or L. geometricus. While most bites result
in mild symptoms, envenomings from both species
have resulted in hospitalisations for symptoms such
as debilitating pain, nausea, vomiting, cramps or vec-
tored bacterial infection in the case of some S. no -
bilis envenomings (Almeida et al. 2009; Dunbar et
al. 2018a; Dunbar et al. 2022b; Earwood et al. 2020;
Goddard et al. 2008). On the other hand, envenom-
ing by Latrodectus hesperus can lead to severe systemic
symptoms (Clark et al. 1992; Nelsen et al. 2014). In
this context, it must be noted that front-line clini-
cians may well be ill-equipped to deal with such
events in areas where L. hesperus is novel; lacking
both knowledge of the treatment for envenomings
and the specific antivenom required. The establish-
ment of any Latrodectus species in Ireland (though
very unlikely) or more frequent introduction of
A h is t ory o f A cc i de n tA l Lat ro d ec t u s in t ro d uc t io ns
117
the automotive trade’s secondary market (e.g. clas-
sic cars) as noted by Nentwig (2015) and Noordjik
(2016). While this is a relatively small market in Ire-
land, a surprisingly large number of Latrodectus spec-
imens do occur in this situation (Nentwig 2015).
The other vectors of the Irish recorded Latrodectus
species must be considered highly unpredictable,
and thus very difficult to monitor efficiently.
Accidental introductions of spiders such as
Latrodectus into Ireland demonstrate how invasive
arthropods are dispersed through global trade. Iden-
tifying why some spider species are more successful
than others in novel environments can provide use-
ful insights into how other potentially invasive spi-
der species might establish themselves and disperse
through other countries. The establishment of La-
trodectus species in new ranges potentially presents
novel medical implications for public health, so leg-
islative action and policy decisions regarding invasive
spider species need to be stressed to governments in
at-risk regions. Of relevance to Ireland is the ab-
sence of legislation in respect of the exotic animal
trade or of a licensing system governing ownership
of exotic animals. Latrodectus species and other po-
tentially dangerous animals can be easily purchased
online, and this represents a potential colonising
route for invasive species. The colonisation of areas
of high endemic significance, such as New Zealand,
Tasmania and the Galápagos Islands, has potential for
negative impacts on the endemic fauna. Identifying
instances where Latrodectus and other alien spiders
are introduced into Ireland and elsewhere is import-
ant to try and prevent establishments.
MATERIALS AND METHODS
IDENTIFICATION OF SPECIMENS
In Case 5 the size, shape, leg banding, and colouration
of the deceased specimen resembled that of the brown
widow spider Latrodectus geometricus (C.L. Koch,
1841). The opisthosoma was badly damaged and the
red hourglass pattern on the ventral surface was not
visible (Fig. 1A, 1C), though this is not a distinct char-
acter in some species (Kaston 1970) and can be highly
variable in different populations of L. mactans (Cabre-
ra-Espinosa and Valdez-Mondragón 2021). However,
the egg sac identified with the specimen was spher-
ical, yellow and had the spikey projections that are
diagnostic of egg sacs of L. geometricus (Fig. 1B). The
identified bodily remains were then used for DNA
extraction and genetic sequencing. As per Fort et al.
(2018), magnetic beads were used to extract DNA
from the specimen. PCR amplification of the Cy-
tochrome Oxidase Subunit 1 gene was done using
the primers coxf3: 5’-GGT CAA CAA ATC ATA
AAG ATA TTG G-3’ and coxFR3: 5’-TAA ACT
specimens into Ireland would increase the possibility
of traumatic envenomings.
Of the Theridiidae spiders that have been intro-
duced to the island of Ireland, only Steatoda nobilis
and Latrodectus geometricus are recognised as globally
invasive (Bauer et al. 2019; Dugon et al. 2017; Garb
et al. 2004; Rayner et al. 2022; Taucare-Ríos et al.
2016). Both have established populations outside of
their native ranges by exploiting urban structures
and synanthropic habitats (Kulczycki et al. 2012;
Sadir and Marske 2021; Vetter et al. 2015; Vetter and
Rust 2012; Vetter et al. 2012). Additionally, both have
similar venom compositions and are responsible for
occasional, comparatively severe envenoming cases
(Khamtorn et al. 2022). Thus, the question can be
posed whether the recent establishment and con-
tinuing spread of S. nobilis in Ireland and the conse-
quent increase in envenoming rates, could possibly
be replicated by a species such as L. geometricus. The
climatic needs of L. geometricus, however, immediately
suggest it is wholly unlikely it could become estab-
lished in Ireland other than possibly in the highly
artificial environment provided by a structure such
as a continuously heated hot house. However, col-
onisation of areas of Southern Europe would seem
to be a possibility given that L. geometricus was previ-
ously collected from steppe habitat in Asia (Bayram
et al. 2008). Other forces, including niche expan-
sions driven by evolutionary adaptation and climate
change, could potentially also allow L. geometricus to
expand its range into Southern Europe in the future
(Guisan et al. 2014; Kobelt and Nentwig 2008).
Returning to a broader consideration of these
introductions suggests that the most likely route
for Latrodectus specimens into Ireland is through
imported grapes, with punnets thereof operating
as vectors in three of the six noted records. The
fruit trade has been a vector for many spider fam-
ilies, both synanthropic (i.e. Pholcidae (C.L. Koch,
1850), Oonopidae (Simon, 1890)) and non-synan-
thropic (i.e. Salticidae (Blackwall, 1841), Linyphii-
dae (Blackwall, 1859)) alike, over the last 40 years
(Kobelt and Nentwig 2008). It is noteworthy that
imports of Peruvian grapes were subject of a trade
assurance agreement between the governments of
Peru and New Zealand in 2012 (Ministry for Pri-
mary Industries 2012). The EU, in 2016, produced
an alert list of potential pests of grapes that might
impact European plants should they become estab-
lished. Four Latrodectus species (L. geometricus, L. has-
seltii, L. hesperus and L. mactans) make the list, but are
included as regularly transported species rather than
actual pests of grapes (Wistermann et al. 2016). Thus,
the Irish records of L. geometricus occurring in grapes
are part of a globally recognised phenomenon. In-
stances of such imports into Ireland, however, must
be very few or there would be more regular reports
of the same. Of greater concern must be that rela-
tively large number of specimens are imported via
Bio lo g y An d En v i ro n m E nt
118
TCA GGG YGA CCA AAA AAT CA-3’ (Dunbar
et al. 2022b). The sequencing results confirmed our
identification of the specimen as L. geometricus. The
sequence was then uploaded to the National Center
for Biotechnology Information (NCBI) via GenBank
(Sayers et al. 2020) and is publicly accessible under the
accession number MK109007.
In Case 6 the size, shape, colouration and pres-
ence of a red hourglass marking on the ventral
surface (Fig. 2A, 2C) indicated that the specimens
belonged to the genus Latrodectus. The van in which
the spiders resided was known to have originated
in California, so the number of possible species was
narrowed to that range. Because of this, Latrodectus
hesperus (Chamberlin and Ivie, 1935) was suspected.
The remains of one specimen were collected and
used for DNA extraction and genetic sequencing
as per above (Dunbar et al. 2022b; Fort et al. 2018).
The sequencing results confirmed the identity of
the spiders as L. hesperus. This sequence is publicly
accessible through GenBank (Sayers et al. 2020)
under the accession number ON746576.
SUPPLEMENTARY DATA
Supplementary video data is available online. Video 1 is
available here: http://muse.jhu.edu/resolve/219. Video
2 is available here: http://muse.jhu.edu/resolve/220.
ACKNOWLEDGEMENTS
The authors would like to thank the Retro Food
Trucks company for access to property for sampling.
We are also very grateful to the anonymous review-
ers whose critical review allowed us to improve
this manuscript. This project was financed through
the Irish Research Council under a Government
of Ireland Postdoctoral fellowship held by JPD
(GOIPD/2021/358).
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