A new subterranean species and an updated checklist of Strumigenys (Hymenoptera, Formicidae) from Macao SAR, China, with a key to species of the Greater Bay Area

Abstract In the past few decades, sampling of leaf litter with Winkler extractors revealed how abundant and ubiquitous ants from the genus Strumigenys are. It is now known that this genus has the third greatest number of species within the Formicidae family. However, very few subterranean species are known, which may be due to the current under-sampling of the soil stratum. Here, a holistic sampling approach, including the use of subterranean traps, was employed in Macao SAR, China. Subterranean traps allowed the collection of a new cryptic ant species: Strumigenys subterranea Brassard, Leong & Guénard, sp. nov. Moreover, extensive sampling of the leaf litter in secondary forests provided four new species records for the genus. The list of Macanese Strumigenys is here updated, elevating the known diversity in Macao to nine species. Furthermore, to facilitate further research on ants of the Guangdong-Hong Kong-Macao Greater Bay Area, a key to the 29 Strumigenys species known from the region is provided. Lastly, recommendations for sampling methods to assess ant biodiversity underground are discussed. In conclusion, this study highlights the importance of using extensive sampling methods, and suggests that relatively small patches of secondary forests within cities can hold a surprisingly high diversity as well as some undescribed species.

introduction With a total of 851 described extant species (AntCat.org 2020), Strumigenys is one of the most diverse ant genera. Primarily distributed within tropical and subtropical regions, several species occur nonetheless within temperate regions (Janicki et al. 2016;Guénard et al. 2017). Yet, the Strumigenys diversity currently reported within tropical regions is likely underestimated. For example, in Southeast Asia, several authors have shown that unrecorded and undescribed Strumigenys species should be expected within several countries (e.g., Guénard et al. 2010;Eguchi et al. 2011;Liu et al. 2015;Jaitrong et al. 2016;Tang et al. 2019). Accordingly, recent work sampling leaf-litter ant communities in Yunnan and Hong Kong resulted in a substantial increase in their known Strumigenys diversity, both because of unrecorded and undescribed species (Liu et al. 2015;Tang et al. 2019).
Morphologically, Strumigenys species are easily distinguished by their small body size, the spongiform tissues on their metasoma (when present), their specialized pilosity and their opposable mandibles (Bolton 1999). Phylogenetically, species of Strumigenys were recently moved from the Dacetini to the Attini tribe based on molecular analyses, strengthening their position as the sister taxon to the phalacromyrmecine ants (Ward et al. 2015). Ecologically, Strumigenys species tend to be associated with primary and secondary forest habitats, with a few species, including several tramp species (e.g., Strumigenys emmae Emery, 1890, Strumigenys membranifera Emery, 1869), relatively common in open and disturbed habitats such as urban parks (Kitahiro et al. 2014;Tang et al. 2019). At the microhabitat level, Strumigenys are typically encountered within the leaf-litter covering forests floors, though a few species nest under bark or epiphytes (Longino 2006), are associated with the accumulated leaf litter in trees (Nadkarni  or forage on the understory vegetation (Lattke et al. 2018). In general, workers of Strumigenys species are collected by leaf litter extractions with Berlese funnels and mini-Winklers. However, these sampling methods may limit the discovery of some Strumigenys species, especially those with subterranean habits. The extraction of soil monoliths and the use of subterranean traps are effective methods to sample the poorly known subterranean ant fauna (Andersen and Brault 2010;Wong and Guénard 2017;Martins et al. 2020). An increase in their systematic use is likely to uncover new species, including within the genus Strumigenys.
Macao is a special administrative region of China located on the south side of the Pearl River Delta. Despite being an under-sampled and heavily urbanized territory with a land area of ~30 km 2 , it nevertheless harbors a surprisingly high ant diversity (Leong et al. 2017). Until recently, few species of Strumigenys were known to inhabit the region. The first Strumigenys record was made by Wheeler in 1928, with the mention of the exotic Strumigenys membranifera. Seventy-eight years later, a second record, Strumigenys sylvestrii Emery, 1906, was published by Hua (2006). This record is, however, most certainly erroneous (Tang et al. 2019). In 2017, opportunistic leaf litter extractions and hand collection expanded the list of Strumigenys species for Macao with four additional species records (Leong et al. 2017). Thus prior to this study, two native (i.e., Strumigenys exilirhina Bolton, 2000 and Strumigenys minutula Terayama & Kubota, 1989) and three introduced Strumigenys species (i.e., S. emmae, S. membranifera, and S. nepalensis) had been recorded in Macao, far less than the 24 species recorded in the neighboring territory of Hong Kong (Tang et al. 2019).
In this study, we used specimens collected through a holistic sampling protocol done to assess the ant fauna of Coloane Island, Macao (Brassard et al. unpublished). In particular, we focus on the Strumigenys species found within the region and report four new species records. Moreover, we describe a species collected with a new type of subterranean trap (M.K.L. Wong, unpublished): Strumigenys subterranea sp. nov. When available, we also provide new sociometric and ecological information for the species collected. Finally, we provide a taxonomic key for the 29 Strumigenys species known from the Guangdong-Hong Kong-Macao Greater Bay Area, a megacity including Macao SAR, Hong Kong SAR, and nine cities in Guangdong province (Hui et al. 2018).
Images were taken with a Leica DFC450 camera mounted on a Leica M205 C dissecting microscope. Image montages of the specimens were taken, stacked, enhanced and measured using the Leica Application Suite v. 4.5.

Taxonomic accounts
Strumigenys subterranea Brassard, Leong  concave anterior margin and a projecting lobe on convex posterior margin, total dental count of eight, lack of propodeal spines, and propodeal declivity angular. Worker description. (Figs 2-4). Head. In full-face view, head noticeably longer than wide (CI: 77) (Fig. 3A), with its widest portion nearby the anterior end of the  Table 1. posterior third of its length. In lateral view, eye with a single facet, inconspicuous, and located at the widest level of the head (Fig. 3E). Posterior cephalic margin shallowly concave; corners of posterior margin of head weakly developed and evenly rounded through the lateral margins. Posterolateral margins evenly rounded on half of their length, then converging at a slightly steeper angle towards the center of the head. Anteromedian clypeal margin slightly convex. Scapes with a moderately developed subbasal lobe on their anterior portion. Apex of scape not reaching posterior margin of head, antenna including scape with six articles, with the last two articles distinctly enlarged and forming a club; ratio of antennal segments from 2 nd to 6 th segment = 3.83 : 1.33 : 1 : 3.05 : 11.56 (Fig. 3D). Mandibles triangular with eight teeth (T) and four denticles (D), arranged from basal to apical as such: T-D-T-T-T-T-T-T-D-D-D-T (Fig. 3C). Basal angle between the basal margin and masticatory margin rounded triangular. Basal lamella a thin strip, widest at the basal tooth and almost fully disappearing at the midpoint of the masticatory margin. Labrum terminates in a pair of short triangular lobes (Fig. 3F).
Mesosoma. In lateral view, dorsum of mesosoma broadly convex but slightly concave at the metanotal groove (Fig. 4A). Anterior portion of promesonotum in dorsal view convex (Fig. 4B), with its widest point slightly posterior to the humeral hairs. Median anterior margin of promesonotum slightly convex. Lateral margin of premosonotum subparallel and slightly convex. Metanotal groove distinct but weakly incised. In dorsal view, propodeum approximately half of the maximal width of the promesonotum. In lateral view, propodeum with an angular declivity. Propodeal declivity with a spongiform lamella.
Metasoma. Petiole in lateral view elongate (LPI: 68) and subclavate, with long and thin peduncle. Petiolar node well developed; dorsum of node convex, with its widest  point at the posterodorsal corner. Petiolar node in dorsal view subcircular (DPI: 64), widest towards the posterior part. Postpetiolar disc in dorsal view suboval and distinctly wider than long; the median portion of the anterior margin distinctly concave whereas the posterior margin convex with a lobe projecting from the median portion (Fig. 4C). Limbus in dorsal view strongly concave, with a thin spongiform pad along its length. Spongiform tissues present on both petiole and postpetiole. Spongiform tissue on the lateral side of petiole restricted to the posterior portion of the node in profile. Excluding the anteriormost part of the ventral portion of petiole, spongiform tissue covers the ventral portion of both the petiole and postpetiole entirely. Depth of spongiform tissue under petiole nearly as much as petiole height. Spongiform tissue particularly extensive on the ventral lobes of the postpetiole. In dorsal view spongiform tissue present along the posterior margin of the petiolar node, and surrounding disc of postpetiole.
Pilosity. On head, spatulate hairs arising from their base and then abruptly curving towards the mandibles, forming a space between the scale of the hair and the head surface. In full-face view of head, numerous evenly spaced spatulate hairs (ca. 95) along the frons, with around two-thirds as much spatulate hairs (ca. 60) evenly spaced but more densely arranged on the clypeus. A total of 16 smaller spatulate hairs present on anterior margin of clypeus. On each side of the anterior margin of the clypeus, three hairs on lateral portion and five on the anterior portion, all incurved towards the midline of the head. Largest spatulate hairs (n = 6) fully extending and found on subbasal lobe of antennal scape; with the first two basal hairs curved towards the apex of the scape, whereas the four most posterior hairs are curved towards the base of the scape. Two pairs of thin remiform hairs on the vertex; with one pair on the lateral portions of vertex and the other in posteromedial position (Fig. 3B). In profile view, appressed simple hairs present below antennal scrobe towards ventral portion of head. On the mesosoma and metasoma, decumbent hairs evenly spaced with a pair of long flagellate humeral hair present on petiolar node; several erected simple, appressed and filiform hairs present on first gastral tergite, whereas other tergites and sternites are mostly covered by appressed simple hairs. Appressed simple hairs present on tibia, femur and tarsus. Meso-and meta-basitarsal hairs flagellate. Flagellate hairs absent from femurs and tibias.
Sculpture. In full-face and lateral view, head covered by areolate sculpturing (0.10 -0.23 mm). In dorsal view, superficial sculpturing on the surrounding of the promesonotum and on its posterior section. Center of the dorsal portion of the promesonotum and propodeum smooth; lateral portions of mesosoma smooth (Fig. 4A). In dorsal view, discs of petiole and postpetiole smooth. In lateral view, petiole with weak sculpturing. Basigastral costulae present as weakly developed and irregular imprints on the central part of the limbus, extending around half the length of the postpetiole disc. Sculpturing on tibias and femurs areolate. Leg bullae absent.
Color. Body coloration concolor yellowish brown, with slightly lighter coloration on the legs, antennae, mandibles and at the apex of the gaster. First gastral tergite and sternite with darker coloration.
Comments. Strumigenys subterranea sp. nov. belongs to the Strumigenys rostrata group of the Malesian-Oriental-East Palearctic region (Bolton 2000), due to a com- bination of morphological characters: mandibles in full-face view triangular, basal lamella of mandible low and rounded-triangular, anterior margin of clypeus broad and shallowly convex, clypeal margin fringed with a continuous row of curved spatulate to spoon-shaped hairs, conspicuous preocular carina, dorsoventrally flattened scape, spatulate to spoon-shaped hairs on leading edge of scape, cuticle within scrobe reticulate or reticulate-punctate, pronotum dorsum without a median longitudinal carina, spongiform appendages present on petiole and postpetiole, pronotal humeral hair present, dorsum of head behind clypeus reticulate-punctate, side of propodeum and disc of postpetiole smooth.
However, S. subterranea sp. nov. can be distinguished from the other 17 species within this group (Table 2) by a combination of the following characters: eyes with a single ommatidia, clypeal margin shallowly convex, evenly spaced appressed spatulate hairs along frons (with appressed spatulate hairs evenly spaced but more densely arranged on clypeus), postpetiole with concave anterior margin and a projecting lobe on convex posterior margin, total dental count of nine, lack of propodeal spines, and propodeal declivity angular, not rounded.
We found that the most peculiar characteristic of S. subterranea (i.e., having very small eyes) is shared with Strumigenys atropos Bolton, 2000. However, the shape of the postpetiolar node (straight anterior margin in S. atropos but concave in S. subterranea sp. nov.) and the shape of the anterior margin of the clypeus differ (slightly convex in S. subterranea sp. nov., but noticeably concave in S. atropos). Moreover, large spatulate hairs are present up to two-third of the length of the lateral margins of the head of table 2. Comparison of five diagnostic characters for S. rostrata group. Characters are (A) appressed spatulate hairs on cephalic region, (B) margin of clypeus convex, (C) anterior margin of postpetiole concave, (D) propodeal spines small or absent and (E) eye composed of a single ommatidium. Values represent the presence (1) or absence (0) of a character.

Species
Characters S. atropos, but not in S. subterranea. Lastly, large spatulate hairs are present on the dorsal portion of the pronotum of S. atropos, whereas hairs on the dorsal portion of S. subterranea are fine. Etymology. The name of this new species refers to the stratum it was collected in and to its suggested subterranean ecology.
Ecology. A single worker from this species has been collected so far, found within a subterranean trap; a 15 mL falcon tube placed at a depth of 12.5 cm below the ground surface. It contained ethanol 70% and was baited with tuna mixed with honey (see Suppl. material 1: Fig. S1 for sampling design). The trap was placed in young secondary forest and was operating continuously for a period of 21 days. Little is known about the ecology of this species. However, due to the extremely reduced eyes present on the specimen and its collection through a subterranean trap, it is here suggested that the species has subterranean habits. Further reinforcing this hypothesis is the fact that extensive sampling in Hong Kong and Macao over the past 6 years focusing on grounddwelling and leaf-litter ants using Winklers and pitfall traps never yielded this species. Nevertheless, only a single worker was found within one out of 256 subterranean traps retrieved during our sampling on Coloane Island, which indicates this species is uncommon. Our data also suggests it cohabits within the same soil layer with other ant species, including other subterranean species. Indeed, we found within the same trap one worker of Pheidole ochracea Eguchi, 2008 and hundreds of workers of Carebara zengchengensis Zhou, Zhao & Jia, 2006. Additionally, within the same quadrat (1 × 1 m) we also found C. zengchengensis at depths of 25, 37.5 and 50 cm, as well as Solenopsis jacoti Wheeler, 1923 and Buniapone amblyops Emery, 1887 at a depth of 50 cm. Figure 5 Smithistruma elegantula Terayama & Kubota, 1989: 788, figs 23-27 (w.q.) TAIWAN.

Strumigenys elegantula Terayama & Kubota, 1989
Indomalaya Pyramica elegantula (Terayama & Kubota, 1989). Combination in Pyramica: Bolton 1999: 1673. Strumigenys elegantula (Terayama & Kubota, 1989 Comments. This is a new species record for Macao. Originally described from Taiwan, this species is more widespread within continental Asia since it has also been recorded in Hong Kong, Macao, Guangdong, Guangxi (China) as well as in Thailand. In both Macao and Hong Kong (Tang et al. 2019), this species is relatively common and is known from two and ten sites within these regions, respectively.
Material  realms, see antmaps.org for a global account (Janicki et al. 2016;Guénard et al. 2017). Within China, found in Hong Kong and Macao.
Comments. Originally from Australia, S. emmae is now a widespread exotic species. Although the exact date at which this species was introduced in the region is unknown, it is known from Hong Kong since the 1990s (Fellowes 1999), and was more recently recorded from Macao (Leong et al. 2017  Comments. This species, first recorded in Macao in 2017 (Leong et al. 2017), is one of the most commonly collected Strumigenys. During the 2019 survey, it was found at 12 different sites within nature parks. In Hong Kong, it is recorded from various habitats including disturbed urban forests, tree plantations, shrubland, secondary forests and Feng Shui woods (Tang et al. 2019        Comments. This species, originally from Africa, is associated with disturbed habitats. For instance, in Hong Kong it was collected near Disneyland and the Hong Kong Airport; two heavily disturbed localities (Tang et al. 2019). The exact date of its introduction in the region is unknown. It was first recorded in Hong Kong in 2019 (Tang et al. 2019), but has been known in Macao since 1928 where it was described from six specimens as S. silvestriana (Wheeler, 1928). As such, its initial introduction to the Greater Bay Area may date beyond a hundred years. Nevertheless, during the 2019 survey in Coloane the species was not frequently collected and was found only in two nature parks, which consisted of relatively small patches of young secondary forests within an urban matrix.
Geographic distribution. China (Hong Kong, Macao, Taiwan), Japan (Ryukyu Islands). Comments. In contrast to Hong Kong, where this species has been rarely collected (Tang et al. 2019), S. minutula was frequently found in Macao since its first collection in 2017 (Leong et al. 2017). Individuals were commonly found within leaf litter samples, and a full colony was also retrieved within one of the ground nests deployed (see Fig. 11). At the time of collection on (29 August 2019), the colony consisted of 135 workers, two dealate queens, eight larvae, and 12 pupae (eggs were not counted). This represents a similar colony size as described previously from Japan, where a polygynous colony of 300 individuals was recorded (Terayama et al. 2014). Note that, on the left foreleg of the queen imaged (Fig. 10E) (Leong et al. 2017). In 2019, of the three sites at which S. nepalensis was collected from, two were heavily disturbed; they consisted of a golf course, and a thin strip of forest bordered by the ocean and a highway. The last one was a patch of young secondary forest nearby another golf course. Our records in Macao support the hypothesis of Tang and collaborators (2019) Figure 13 Pentastruma sauteri Forel, 1912: 51 (w.) Taiwan. Indomalaya. Pyramica sauteri (Forel, 1912). Combination in Pyramica: Bolton 1999: 1673. Strumigenys sauteri (Forel, 1912 Key of the twenty-nine Strumigenys species recorded from the Guangdong-Hong Kong-Macao Greater Bay Area

Strumigenys sauteri Forel, 1912
The following key relies heavily on couplets elaborated by Bolton (2000), which were subsequently used for a key to the Strumigenys (as Pyramica) of China (Xu and Zhou 2004). For species present in the Greater Bay Area that are within Bolton's key, we used his couplets. New couplets were added for species absent from Bolton's key.

1
Mandibles relatively short, not kinetic, not forming a snapping mechanism (Fig. 14A). Maximum opening of mandibles 90° or less (17 spp.) .............. 2 -Mandibles relatively elongate, edentate along inner margin and forming a snapping mechanism (i.e., trap-jaw) (Fig. 14B). If not elongate, mandibles forming a snapping mechanism, either curvilinear (Fig. 14C) or with outer margin flared outwards near base and with strongly projecting basal angle (Fig. 14D). Maximum opening of mandibles 170° or more (12 spp. With head in full-face view, the leading edge of the scape with a row of conspicuous projecting curved hairs, of which one or more, distal to the subbasal bend, distinctly curved toward the base of the scape (Fig. 19A). These hairs may be spatulate, remiform, spoon-shaped or broadly clavate apically; basal stem of each hair (which may be short) erect or sub-erect with respect to the long axis of the scape (4 spp. Two pairs of thin remiform hairs on the vertex, with one pair on the lateral portions of vertex and the other in posteromedial position (Fig. 24B). Dorsum of promesonotum with erect simple hairs ( Apical half of mandible with two preapical teeth, the proximal slightly longer than the distal. With alitrunk in profile posterior surface of mesonotum narrowly convex and weakly bulging, overhanging the metanotal groove. Posterodorsal corner of propodeum dentate. Head broader than long ( With head in full-face view, the outer margins of the fully closed mandibles intersect the anterior clypeal margin mesad of the anterolateral clypeal angles, so that there is a section of the anterior clypeal margin that projects laterally beyond the outer line or the mandible (Fig. 36A). Small to minute species With head in full-face view, the fully closed mandibles triangular, with teeth present along entire length of exposed inner margin (Fig. 39A); proximal half or inner margin dentate, without a long diastema between basal tooth and basal lamella; without a large space basally through which the apices of the labral lobes are visible ( Fully closed mandibles in full-face view very broad proximally and strikingly tapered distally, obviously not linear or curvilinear (Figs 43, 44C). Outer margin of mandible flared outwards near base and with a strongly projecting prebasal angle (China: Hong Kong ; Indonesia: Java ; Thailand, Vietnam) ....S. sydorata -Fully closed mandible in full-face view not very broad proximally nor strikingly tapered distally, linear (Fig. 44A) or curvilinear (Fig. 44B). Outer margin of mandible not flared outwards near base, without a strongly projecting prebasal angle ( -Preapical tooth of mandible varying from a denticle to a triangular tooth but not spiniform, the tooth shorter than the maximum width of the mandible, usually distinctly shorter (Fig. 55B)

Discussion
Traditionally, Strumigenys species have been collected through the extraction of arthropods present in the leaf litter, which is here confirmed with the capture of eight out of nine species through this method. However, the addition of subterranean traps allowed the collection of an undescribed species: Strumigenys subterranea sp. nov. If the majority of Strumigenys species are not considered subterranean, but rather leaf-litter foragers or even arboreal Lattke et al. 2018), a few exceptions occur. For instance, the species Strumigenys hexamera Brown, 1958 (Masuko 1984) and Strumigenys mitis Brown, 2000 (Mezger and Pfeiffer 2010) are considered subterranean, while other records suggest a potential subterranean lifestyle in other species such as in Strumigenys sp. nr. sutrix Bolton, 2000, for which 2 individuals were collected with subterranean traps at a depth of 5 cm (Andersen and Brault 2010). Subterranean ants have adaptations, such as specific morphological characteristics, to live within the particular environmental conditions that define the underground habitat (Wong and Guénard 2017). Among those, the absence of eyes or the presence of reduced eyes, while not strictly limited to subterranean ants (e.g., some epigaeic army ants), represent an adaptation to this obscure environment. Indeed, visual ori- entation underground should be limited if non-existent, thus rendering obsolete the need for large eyes providing a more acute vision. The presence of short mandibles, presumably easier to maneuver underground than the long and snapping mandibles of certain trap-jaw Strumigenys, potentially represents another adaptation. For instance, S. hexamera is a sit and wait predator that uses its short mandibles to hunt preys within tunnels (Masuko 1984), while the short triangular mandibles of the subterranean S. mitis have been proposed as a subterranean adaptation in contrast to the long and wide-opening mandibles of the epigaeic S. rotogenys (Mezger & Pfeiffer, 2010). Since Strumigenys subterranea sp. nov. possesses both characteristics (i.e., reduced eyes and short triangular mandibles) and was detected at 12.5 cm below ground, this would suggest a subterranean lifestyle. Nevertheless, mentions of subterranean Strumigenys are still rare, which may be due to very limited sampling efforts within this stratum (Wong and Guénard 2017).
To collect subterranean Strumigenys, other techniques than subterranean traps exist. For instance, Strumigenys louisianae Roger, 1863, Strumigenys nr. epinotalis Weber, 1934 and Strumigenys denticulata Mayr, 1887 were retrieved using soil monoliths at a depth of 0-10cm (Martins et al. 2020), while the holotype worker of Strumigenys fuarda Bolton, 2000 was collected within a soil core (Bolton 2000). However, soil sampling, if done without removing the upper soil layer, does not preclude the collection of leaf litter ants foraging on the upper surface of a core or monolith. This is potentially the case for S. louisianae or S. nr. epinotalis (Martins et al. 2020), and as such further observations are required to establish if they are hypo-or epigaeic.
Another sampling method that can potentially collect subterranean Strumigenys is nest excavation, which has been used to collect nests of the subterranean S. hexamera (Masuko, 2013). Moreover, excavations under the litter-fermentation-humidification horizon up to a depth of 25 cm found nests of Strumigenys kumadori Yoshimura & Onoyama, 2007 (Masuko 2010). However, nest excavations do not ensure that the species collected are subterranean, because even though these species may nest underground, their foraging activity could be mainly occurring above ground. As such, labeling an ant as subterranean solely because it was collected during an excavation is not fully satisfactory. As an example, S. kumadori, which has relatively large eyes and long snapping mandibles, does not match the morphology of an hypogaeic species. Thus, to collect subterranean Strumigenys species, subterranean traps or the careful excavation of soil monoliths (of which the top soil layers would be excluded) seem to be preferential solutions.

Conclusions
Although cities and the nature parks within them (i.e., patches of secondary forests) are rarely viewed as a refuge for biodiversity, recent work using diverse sampling approaches have shown that urban habitats can host high numbers of both native and exotic ant species Leong et al. 2017). This study in Macao, as well as recent work in Hong Kong (Tang et al. 2019) -two heavily urbanized regions -shows that both regions support a high diversity of Strumigenys species, with nine and 24 species recorded respectively. Recent work in other parts of the world, such as in the USA, also showed that the discovery of new Strumigenys species within urban habitats is possible (Longino and Booher 2019). Alarmingly, further urbanization threatens several of these habitats, including the type locality of the species described here. Indeed, a construction project is planned in proximity of where the only specimen of Strumigenys subterranea sp. nov. was found, which could potentially impact key habitats for this species. In summary, the current study supports both the ideas that urban areas can hold a surprisingly high biodiversity for particular taxa as well as to contain species novel to science. As such, it is worth protecting forest patches within cities, and using extensive sampling methods to discover and describe what lurks amongst our dwellings.