A systematic sampling of the complete arthropod fauna in the interior of homes and an understanding of the role that interior microhabitats play in determining the assemblage of arthropod communities are the first steps toward revealing ecological dynamics in a vastly understudied system ( Baz & Monserrat, 1999 ; Dunn et al., 2013 ). What are the most prevalent arthropod groups found in houses and how common are they among homes and rooms? Here we explored the composition of overall arthropod diversity, including both pest and non-pest species, in human dwellings. Through surveying 50 free-standing houses located in the North Carolina Piedmont region, we identified and characterized the overall diversity of arthropods found within these homes. 
 
 Research on indoor arthropod communities has focused almost exclusively on pests, with a particular emphasis on those of medical and economic importance such as cockroaches, termites, bed bugs, fleas, and mosquitoes ( Committee on Urban Pest Management et al., 1980 ; Robinson, 2005 ). Unlike the species that threaten or bother us, very little is known about the myriad other arthropod species, many of them inconspicuous (and even unnoticed), that live with humans. The true interactions between these other species and humans—be it beneficial, neutral, or negative—remain largely unknown, as does their prevalence and distribution. In fact, a comprehensive survey of arthropod life in contemporary human houses has never before been carried out. 
 
 In contrast to the simple dwellings early humans used, modern western houses are perceived of as being an environment largely devoid of animal life. However, arthropods thrive in homes, as evidenced by today’s multi-billion dollar pest control industry. Houses today host many of the same pest groups found in archeological sites (see ‘Results’), yet today’s arthropod communities also reflect aspects of society’s modernization. For example, with the advent of indoor plumbing, dung beetles (Scarabaeidae) are less prevalent indoors (as shown in this study), but drain-dwelling moth flies (Psychodidae) are likely more so. Also, as human society became more globalized through travel and trade, arthropod species that are closely associated with humans and their homes, such as the house fly ( Musca domestica L.; Legner & McCoy, 1966 ), German cockroach ( Blattella germanica L.), and fruit fly (or vinegar fly, Drosophila melanogaster Meigen; Keller, 2007 ) obtained worldwide distributions and, in some cases, even lack wild populations (e.g., the German cockroach; Roth, 1985 ; Booth et al., 2010 ). The influence of human society and our changing domiciles on the evolution of specific arthropod lineages is evident. 
 
 Insects, spiders and their relatives have been living and evolving with humans for all of our history. It has been proposed that many arthropod species that are now associated with human houses were originally cave dwellers (e.g., bed bugs: Cimicidae) ( Balvín et al., 2012 ). Evidence of arthropod vectors in caves inhabited by prehistoric people ca. 26,000 years ago suggests that pestiferous arthropods, such as blood-feeding kissing bugs (Reduviidae: Triatominae), lived alongside our ancestors ( Araújo et al., 2009 ). Among the first examples of cave art is a depiction of a camel cricket (Rhaphidophoridae) ( Chopard, 1928 ; Belles, 1997 ). 
 
 For as long as humans have lived in fixed habitations there have been other organisms that dwell alongside us. We share our living spaces with a variety of invited and uninvited guests spanning the tree of life, from large vertebrates (e.g., pets and livestock) to microorganisms ( Martin et al., 2015 ). The most diverse and abundant group of multicellular life found in homes, as well as on Earth more generally, is represented by arthropods. 
 
 We classified rooms into 6 categories based on their similarities of features and use: attics, basements (including finished and unfinished basements, and crawl spaces), bathrooms (including bathrooms and laundry rooms), bedrooms (including bedrooms, offices, and libraries), common rooms (including living rooms, dining rooms, and attached hallways), and kitchens (including kitchens and pantries); rooms not conforming to one of the categories were classified as “other” and were excluded from Table 1 . We estimated diversity of families based on the complete list of families acquired over each sampled house using the Chao2 Estimator with 1,000 randomization runs in EstimateS ( Colwell, 2013 ). We compared total dust mite abundance in each sample with the floor type on which it was collected. Some samples were collected on carpet, while others were on bare surfaces. Because the data were not normally distributed, we analyzed the differences between samples with different floor types using a Kruskal–Wallis test. All analyses were done in R 3.1.2 ( R Core Team, 2015 ). 
 
 We identified all specimens to family level except when specimens were badly damaged or required additional methods for identification (e.g., slide mounting of mites and other taxa). We further determined genera and species when possible, but many specimens could not be identified to such a level for several reasons including, but not limited to, being damaged, being an unidentifiable sex (e.g., female Sciaridae) or an unidentifiable life stage (e.g., larvae), or being a group that is understudied or lacking good diagnostic keys. As such, our approach produced a very conservative list of morphotaxa for each room in the house and hereafter we call these morphospecies; this type of characterization has been found to be effective in comparing species richness and turnover between sites ( Oliver & Beattie, 2002 ). The taxonomic identity of morphospecies was not compared between rooms within homes due to limitations on time, space (storage of voucher specimens) and diagnostic expertise, thus the true number of morphospecies per house and among all houses was not definitively determined. Thus, a conservative (or assumed minimum) estimate of morphospecies richness per house was created by taking the maximum number of morphospecies from the room containing the highest number of morphospecies, for each family, and summing the total. This is in contrast to a maximum estimate of morphospecies richness which was the total sum of all morphospecies from all rooms within a house; this maximum corresponds to the case in which no two rooms held the same morphospecies. We assume the true diversity falls between our minimum and maximum estimates. All voucher specimens are housed in vials of ethanol in the laboratory of RRD (Department of Biological Sciences, NCSU) for use in further ecological, genetic, and microbiological studies. Specimens will be deposited in the insect museum at NCSU (Department of Entomology) when permanently housed. 
 
 We sampled dust mites from the middle of the master bedroom floor, regardless of floor type, in a 0.5 m 2 area. To collect mites, we used a vacuum that was adapted to use specimen cups modified with a screen bottom composed of mesh with 0.0055 inch (0.1397 mm) openings, small enough to allow air to pass through but not mites. We stored all samples in 95% ethanol until they were sorted and quantified. Because of time and specimen handling constraints, only five individuals from five randomly-selected samples were identified. 
 
 We (trained entomologists) performed a visual inspection of each room and collected specimens by hand using forceps, aspirators and entomological nets. Only visible surfaces, including those accessible under and behind furniture, around baseboards, ceilings, and on shelves and other surfaces were sampled. We collected all arthropods or putative arthropods, including those from spider webs; both living and dead arthropods were collected in this manner into vials containing 95% ethanol. We did not collect all specimens of a given arthropod species. We designated each distinct room or area and labeled its vial with the room name (as best identified), floor type, and number of windows and doors to the outside of the house; doors between rooms were not quantified. We identified floor types as wood (including laminates, hardwoods, and other wood-like surfaces), linoleum (tiles or otherwise), tile (stone, concrete, or otherwise; not including linoleum) or carpet. The presence of small or large rugs on other surfaces was noted as well. Typical room categories included kitchens, bedrooms (sometimes specified as offices/dens because of their lack of running water, but not receiving the same amount of traffic as common areas), bathrooms, laundry/utility rooms (denoted when a washer and dryer were present), and common areas. Common areas consisted of large open areas that were not easily categorized, usually including dining rooms, living rooms, front rooms, hallways, etc. Closets were sampled and included with the room in which they opened. When a room was present on a floor other than the first/main floor, house level was recorded (e.g., “2nd Floor Bathroom”). All rooms inside the house were sampled in the manner described above except for attics and crawl spaces, which were sampled less thoroughly: only the entrance of each was sampled within a 2 m radius. The limited sampling method for these areas was deemed necessary for the safety of those collecting the specimens (i.e., to avoid high summer temperatures in attics and confined areas in crawl spaces). Screened porches, decks, garages, detached sheds/structures, and closets accessible only from the outside were not sampled. 
 
 We solicited volunteers owning or renting free-standing homes in Raleigh and neighboring areas of North Carolina, USA. The study area is located in the Piedmont of the state and characterized by red clay soils and deciduous/pine forests (with meadows and aquatic/semi-aquatic systems interspersed) among various urban and suburban development ( Fig. 1 ). We randomly selected 50 homes/volunteers to visit from among participants who filled out an online questionnaire about the characteristics of their household and behavior of its residents. All homes included in the study were within a 30 mile radius of Raleigh’s center (35.7719°N, 78.6389°W). Each home was visited once between May and October 2012. Upon arrival, volunteers were informed of the procedures and process for sampling arthropods and asked to sign a consent form ( Supplemental Information 1 ). 
 
 Arthropods were found on every level of the home and in all room types. Only 5 rooms (non-attics) had no arthropod specimens collected (four bathrooms, one bedroom). Six arthropod orders dominated houses, comprising 81% of the diversity in an average room: Diptera (true flies, 23%), Coleoptera (beetles, 19%), Araneae (spiders, 16%), Hymenoptera (predominantly ants, 15%), Psocodea (book lice, 4%), and Hemiptera (true bugs, 4%) ( Fig. 5 ). Eight additional orders made up another 15% of the diversity (Blattodea, Collembola, Lepidoptera, Isopoda, Zygentoma, Polydesmida, Orthoptera, and Acari), while all remaining orders comprised a total of 4% of the overall diversity ( Fig. 5 ). The percentage of rooms in which an arthropod was collected varied among taxa, as did their presence in rooms of different types ( Table 1 ). 
 
 Typical household pests were found in a minority of the homes, such as German cockroaches ( Blattella germanica : 6% of houses), subterranean termites (Rhinotermitidae: 28% of houses), and fleas (Pulicidae: 10% of houses); bed bugs ( Cimex lectularius Linnaeus) were not found during the study. Larger cockroaches (Blattidae), such as smoky brown ( Periplaneta fuliginosa (Serville)) and American cockroaches ( Periplaneta americana (Linnaeus)) were found in the majority of houses (74%). However, the American cockroach (which is the only of the two considered a true pest) was only recovered from three homes; smoky brown cockroaches made up the vast majority of large cockroaches collected. All pest species were less common than other more inconspicuous arthropods such as pillbugs (Armadillidiidae, 78%) and springtails (Entomobryidae, 78%). 
 
 While overall diversity was high, 12 frequently found families were identified in at least 80% of homes ( Fig. 4 ). Only four families were identified from 100% of houses sampled: cobweb spiders (Theridiidae), carpet beetles (Dermestidae), gall midge flies (Cecidomyiidae) and ants (Formicidae). Book lice (Liposcelididae) and dark-winged fungus gnats (Sciaridae) were found in 98% and 96% of homes, respectively. Nearly half of all families (five of 12) found in over 80% of homes were true flies (Diptera): fungus gnats (Sciaridae); mosquitoes (Culicidae); scuttle flies (Phoridae); non-biting midges (Chironomidae); and gall midges (Cecidomyiidae). 
 
 Twelve (12) families were represented in at least 80% of homes. For each family we present the common name and percentage of homes it was found in, followed in parentheses by the scientific family name and species level identification when possible. (A) cobweb spiders, 100% (Theridiidae; shown here Parasteatoda tepidariorum (Koch)); (B) carpet beetles, 100%, (Dermestidae; shown here Anthrenus larvae); (C) gall midges, 100% (Cecidomyiidae); (D) ants, 100% (Formicidae; shown here Monomorium minimum (Buckley)); (E) book lice, 98% (Liposcelididae); (F) dark-winged fungus gnats, 96% (Sciaridae); (G) cellar spiders, 84% (Pholcidae; shown here Pholcus sp.); (H) weevils, 82% (Curculionidae; shown here Sitophilus zeamais (Motschulsky)); (I) mosquitoes, 82% (Culicidae; shown here Aedes albopictus (Skuse)); (J) scuttle flies, 82% (Phoridae; shown here Dohrniphora incisuralis (Loew)); (K) leafhoppers, 82% (Cicadellidae; shown here Sibovia sp.); (L) non-biting midges, 80% (Chironomidae). All photos by MAB. 
 
 The number of species collected by house is represented by the middle bar. The bottom limit is the minimum/conservative estimate of morphospecies by house which was calculated by taking the maximum number of morphospecies from the room containing the highest number of morphospecies, for each family, and summing the total The upper limit is the maximum possible of morphospecies within a house, with the assumption that each set of morphospecies within each room were unique from other rooms. Houses furthest to the left are the smallest in terms of square footage, and those furthest to the right are the largest. Houses ranged in size from 840 to 4,833 square feet. 
 
 We collected 24–128 families from each house, resulting in an average of 61.84 (s.d. = 23.24) distinct arthropod families per house and a total gamma diversity (across houses) of 304 families ( Fig. 2 ). One hundred and forty-nine (149) families were rare, collected from fewer than 10% of homes, 66 of which were found in just a single home. The number of families collected in a home was correlated with house size ( r 2 = 0.3, p = < 0.001). Conservative species estimates by home ranged from 32 to 211, with an average of 93.14 (s.d. = 42.34) morphospecies per house ( Fig. 3 ). Considering that our conservative species estimate assumes that rooms with the greatest number of morphospecies by family included all species from other rooms (which is almost certainly untrue), this number is likely much lower than the true number of species per house ( Fig. 3 ). 
 
 Houses in the study ranged from 840 to 4,833 square feet in area (mean = 2,072; median = 1,720) and were from seven to 94 years old (mean = 41.35; median = 30.5). During the course of sampling 554 rooms in the 50 homes, over 10,000 specimens were collected and identified. These specimens represented all four subphyla (Chelicerata, Myriapoda, “Crustacea,” and Hexapoda), as well as six classes, 34 orders and 304 families of arthropods ( Table 1 and Table S1 ). While we cannot determine the exact number of morphospecies that were collected, there were at least 579 morphospecies based on our most conservative estimates (calculated by summing the maximum number of morphospecies for each family ever found in a single room). 
 
 Discussion 
 
 As household pests and disease vectors, the indoor arthropods in our daily lives have had a substantial impact on human society both historically and today. Although extensive research has been done on a small number of arthropod pest species, the data presented herein represent the first comprehensive survey of the arthropod diversity collected from urban and suburban houses. In the absence of similar studies that could provide baseline data for comparison, our results are surprising both in terms of the prevalence of arthropods (virtually every room was occupied) and in terms of their diversity. 
 
 The diversity of arthropods found indoors extends far beyond commonly recognized species. We found that an individual house may have hundreds of arthropod species within it, with each house on average containing 62 families and a minimum estimate of 93 morphospecies. The true diversity among these 50 homes is undoubtedly much higher due to limitations of the minimum estimate (it assumes no species turnover between rooms), the presence of cryptic species and our sampling method that excluded areas behind walls, under heavy furniture, and in drawers and cabinets, all of which undoubtedly serve as potential refuges for additional arthropods. While sampling 50 homes did lead to a decrease in the estimated diversity of families, clearly there are still many other families and morphospecies that are yet to be recovered and characterized from homes (Fig. 2). 
 
 We found that four groups of arthropods dominate the average room: flies (23%), beetles (19%), spiders (16%) and hymenoptera (predominantly ants, 15%) (Fig. 5). Overall, there are more types of flies associated with human homes than any other group of animals. Some flies have evolved close associations with humans, while others (Chironomidae and Cecidomyiidae) may arrive in houses as part of ‘air plankton’; their presence indoors is more a reflection of their abundance outdoors than of the ecology inside homes. Despite their prevalence, flies represent only a small proportion of taxon-focused studies in the urban landscape (McIntyre, 2000). Recent studies have revealed new information on flies in urban landscapes, including 30 new scuttle fly species identified from urban Los Angeles (California, USA), indicating that the true diversity of these flies, and likely many other small fly groups, in human-developed areas is underestimated (Grimaldi et al., 2015; Hartop, Brown & Disney, 2015). 
 
 Book lice (Psocodea: Liposcelididae), were found to be among the most ubiquitous indoor arthropods (found in 49 of 50 houses). Book lice are close relatives of parasitic lice and have a long evolutionary history of living, among other places, in close association with birds, mammals and their nests (including those of primates; Grimaldi & Engel, 2005). As stored grain pests, fungus feeders, and scavengers, book lice thrive in indoor environments. Liposcelis bostrychophila Badonnel, for example, is a globally-distributed, anthropophilic species whose widespread success and resistance to control measures is in part due to its parthenogenesis, ability to disperse through air, wide diversity of diet, and resistance to starvation (Diaz-Montano et al., 2014). Book lice have become more common in houses in the United Kingdom over time (recovered from 14% of houses sampled in 1987 versus 30% in 1997; Turner & Bishop, 1998) and are more prevalent in areas of high humidity in houses in Spain (such as kitchens and bathrooms; Baz & Monserrat, 1999). However, perhaps due to North Carolina’s humid climate or our sampling methods, we found book lice distributed throughout houses. 
 
 Dust mites were found in the majority of homes (76%). Previous studies have found dust mites in 30–100% of sampled homes across the US (Arlian et al., 1992). Human association with dust mites may have been established with the origins of dense human settlements; dust mites likely shifted from the nests of synanthropic birds or rodents to human houses (Klimov & O’Connor, 2013). To control dust mite populations, it is often recommended to remove carpets because they provide protection, thermoinsulation, higher humidity, and trap the food on which these mites feed (Colloff, 1998). As expected, we found much higher dust mite abundance on carpeted surfaces, consistent with previous research. Yet, paradoxically, the house that had the single highest abundance of dust mites within our study had a wood floor. Humidity levels and vacuuming frequency, although unknown for this house, may explain the discrepancy. Characteristics of different wood floors, such as age and quality of build, could also affect mite abundance since gaps between boards can provide habitat for mite populations. 
 
 Because previous studies of indoor arthropods have largely focused on pest groups of economic and human health importance (e.g., Runstrom & Bennett, 1990; Colloff, 1998; How & Lee, 2010; Crissman et al., 2010), we expected common pests to be among the most frequently found groups of arthropods in the homes. In fact, we found a relative dearth of typical household pests. The only exception to this was the prevalence of the smoky brown cockroach, a species that is not truly considered pestiferous because it does not generally develop pest-level populations in homes due to its need for high humidity and moisture (Robinson, 2005). It may be that we collected more specimens of this species due to their intolerance and ultimate death within the homes. While the lack of many pest species could be an artifact of the sampling design (sampling for species occurrence rather than abundance, as well as sampling in free-standing homes rather than other forms of human habitation such as apartments, townhouses, etc.), it appears that the vast majority of arthropods that live among us cause no direct harm. Unfortunately, many insects and arthropods we collected are considered pests based solely on their presence in the home (i.e., nuisance invaders; Hahn & Ascerno, 1991; Cranshaw, 2011), despite having no direct impact on people or their possessions. 
 
 Many arthropods we identified from houses were unexpected—either in terms of the frequency with which they were found or because they are rarely found outdoors, much less indoors. Gall midges (Cecidomyiidae), although found in every house sampled, were not even mentioned among the over 2,000 species listed in a recent compilation of urban insects and arachnids (Robinson, 2005). Leafhoppers (Cicadellidae), as plant feeders, are not associated with the indoor biome (Robinson, 2005), yet were among the groups most frequently found in houses. Moths and butterflies (Lepidoptera), on the other hand, were collected infrequently, making up only 2% of the average diversity in a room; this is disproportionate to their known overall diversity (the order comprising over 10% of described insect species; Heppner, 2008). Although ants (Formicidae) were expected and found in 100% of houses, further identification at the genus and species level revealed taxa that are not typically thought to occur in homes. Camel crickets (Rhaphidophoridae) are known basement dwellers in the Southeastern US, but our sampling confirmed previous reports that an invasive species, Diestrammena asynamora (Adelung) predominates over native species (Ceuthophilus spp.) (Epps et al., 2014). Other unexpected finds were ant-loving crickets (Myrmecophilidae), the smallest orthopterans (Whitman, 2008), which were found in homes with ant infestations; beetles from the relatively rare suborder Archostemata (families Cupedidae and Micromalthidae); and a larval beaded lacewing (Berothidae), a rarely seen neuropteran known to live within termite nests where they paralyze termites with an airborne chemical before feeding on them (Johnson & Hagen, 1981). 
 
 Of the arthropods we found that live out a portion of their life cycle in human houses, there is a broad diversity of trophic levels and life histories represented. Apart from a few herbivorous arthropods associated with houseplants or those inadvertently living indoors (for example, brought in on cut plants), most taxa sampled from houses were either scavengers, predators, or parasitoids. Carpet beetles (Dermestidae) were found feeding on dog kibble, dead insects and nail clippings. Other scavengers, like silverfish (found in 68% of homes) and book lice were also common. Carrion-feeding flesh flies (Sarcophagidae) were found during the study emerging from a rodent killed by a house cat. Spiders (including spitting spiders, Scytodidae, that spit venom up to a centimeter to ensnare prey; Foelix, 2011) and centipedes (especially Scutigeridae) were the primary predators sampled. Minute parasitoid wasps (especially Eulophidae and Platygastridae s.l.) that potentially parasitize other household arthropods were also common inhabitants. For instance, one species of Eulophidae, Aprostocetus (Tetrastichodes) hagenowii (Ratzeburg) (Table S1), a known parasitoid of blattid cockroach egg cases (oothecae), was commonly collected in homes as were its hosts. Considering the range and abundance of life histories found in our study, the trophic dynamics of the indoor ecosystem is an area in need of future study. 
 
 The rich arthropod diversity we identified from houses reflects a gradient of association with human habitations, from synanthropic arthropods that appear strongly adapted to human houses (cobweb spiders, carpet beetles, book lice), to others that seek shelter and resources only on occasion (ants, ground beetles, hunting spiders, smoky brown cockroaches), to many groups that simply become trapped in houses to their own detriment (leafhoppers, gall midges, click beetles). Most of the arthropod groups we identified do not have life histories that are known to be closely associated with the indoors. Many arthropods may find themselves indoors as a result of the ‘Malaise trap effect’: houses, like Malaise and other flight intercept traps, are effective at capturing local arthropods that may be travelling through the environment or are attracted to houses by artificial light, food, and shelter. These arthropods may be active in a house for a short period of time, where interactions between them and the house’s residents may occur, but eventually they must either find an exit or succumb to mortality. The idea that homes are traps or filters of local, outdoor arthropod fauna implies the importance of further investigating the dynamics between the greater landscape and the indoor environment. 
 
 Biodiversity in urban landscapes is richer than was once thought (McKinney, 2008; Fattorini, 2011; Fattorini, 2014), and we find here that the indoor, manufactured environment also supports more diversity than anticipated. These findings represent a new understanding of the makeup of the indoor arthropod community and their distribution within houses. Arthropods within our homes are both diverse and prevalent, and are a mix of closely synanthropic species and a great diversity of species that wander indoors by accident. Many species we found were unexpected, unnoticed by residents until they were collected, and play no pestiferous role in human houses. Yet, further research on the ecological dynamics of the indoor biome is needed to understand the potential economic and health implications of the species that live and have evolved in such close proximity to us. ||||| Matt Bertone 
 
 If only they paid rent. There are on average 100 species of creepy-crawly in every house, according to the first comprehensive census of house-dwelling arthropods. 
 
 Some are part of an intricate ecosystem that relies on crumbs and nail clippings for food. Others are accidental visitors trapped in this strange and dangerous world, unbeknownst to most homeowners. 
 
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 The survey found 579 species, mainly insects, spiders, beetles, mites, flies and ants, in 50 detached houses in the leafy suburbs of Raleigh, North Carolina. “The residents were really surprised and often horrified that we found so much, so we had to calm them down by saying it was normal,” says Matt Bertone of North Carolina State University in Raleigh, who led the survey. 
 
 He says the results dispel ideas that modern homes are sterile deserts, showing instead that they teem with unseen life. “The biggest surprise was finding at least one species in almost every room, with only five of the 554 rooms drawing a blank,” says Bertone. Some have adapted to live in human homes permanently, such as cobweb spiders and booklice. 
 
 Bertone says that the species the team spotted most frequently are known to be abundant worldwide, but the exact proportions of creatures found in this suburb may differ from those in inner-city tower blocks or rural houses. 
 
 Home ecosystem 
 
 The arthropods were found anywhere from carpets and floorboard cracks to shelves and skirting boards. 
 
 The good news is that most are unlikely to harm you or your house. In fact, many pest species, such as bed bugs or German cockroaches, were absent from most of the houses. 
 
 The only creatures found in every home were ants, carpet beetles, cobweb spiders and gall midges. “They rely on things we produce or have in our homes,” says Bertone. 
 
 Taken together, these regulars form a neat ecosystem, with spiders and centipedes as apex predators, hunting smaller fry such as carpet beetles and other spiders. 
 
 The carpet beetles and book lice do much of the clearing up, scavenging dead insects, moulds and algae, as well as polishing off food crumbs and detritus from our own bodies, including nail clippings, hair and dead skin. Some carpet beetles live on and consume spiders’ webs. 
 
 Personal jungle 
 
 Other species, such as house flies, stray in temporarily, maybe for food or warmth in harsh weather. Still others come in by accident and are usually trapped and doomed once indoors. 
 
 “The indoor environment has proved to be full of unexpected biological diversity and houses are our own personal jungles,” says Anne Madden of the University of Colorado at Boulder. “We clearly have much to learn about the potential food webs in our homes.” 
 
 “Understanding the life that permeates our dwellings is essential to establishing the influence of our indoor life on our health,” says Jack Gilbert of Argonne National Laboratory in Illinois. “Insects have their own bacteria and move them round a house, so by understanding their biodiversity, we can better explain the distribution of microbes around our homes.” 
 
 Another recent survey of 1200 households across the United States found that household dust holds an average of 9000 different species of bacteria and fungi. 
 
 Gallery 
 
 See seven of the creepy-crawlies found lurking in homes 
 
 Journal reference: PeerJ, DOI: 10.7717/peerj.1582 
 
 Read more: “Why insects are the real rulers of the world“ ||||| How many insects do you think are in your home? None? One? A hundred? Some new research suggests you need to step that number up by a factor of 10. Or more. But don't panic: Insects and their relatives are living peacefully in your home. They aren't bothering you. Well, except psychologically, now that you know hundreds of them are there. 
 
 Entomologists have been saying for years it's not possible to have a completely bug-proof home; now there are numbers to back that up. Scientists carefully collected all the arthropods (insects, spiders, mites, and crustaceans, among others) they found in 50 homes in North Carolina. In every single home they examined, they found extra residents. Of 554 rooms in those homes, all but five (less than 1 percent) had some crunchy squatters. If you think your house is spotless and bug-free, you are wrong. When you move into an empty house, it’s not really empty. You have roommates. 
 
 Over 400 people volunteered to have entomologists search their homes for bugs after a public call for participation. Because really, how often do you get to have a group of PhDs crawl around your house on their hands and knees for free? 
 
 The research group chose a representative selection of homes, big and small, from 7 to almost 100 years old. They limited themselves to visible surfaces under and behind furniture, baseboards, ceilings, and shelves. I asked researcher Matt Bertone what it was like to knock on a someone's door, introduce yourself, and then spend hours crawling around their floor with a headlamp and tweezers. He said it wasn’t awkward until the end (well, more awkward than what you’d expect if a complete stranger looked under your couch and bed). 
 
 Before leaving, the collection team reviewed what they found with the homeowners. It was a bit of a shock for some. “I think they thought we would only find a few things, and we would come back with hundreds of specimens,” said Bertone. His team collected and identified more than 10,000 specimens during the course of the study. On average, more than 93 different species lived in each home. And that is an extremely conservative estimate. 
 
 Bertone et al 2016 
 
 All the houses examined contained flies, beetles, spiders, and ants. Almost all of the houses (98 percent) contained booklice, harmless tiny insects you’ve probably never heard of. Booklice eat mold and mildew, commonly found in starchy paste of books and wallpaper. 
 
 Don’t start pricing flamethrowers on Amazon just yet. “It's very benign," says Michelle Trautwein, co-author on the study. "We all have these quiet roommates that really don't have a lot of negative impact on our lives.” Most of the arthropods found were described by the researchers as “air plankton"; they were accidental entrants into the home that got trapped and died there. 
 
 For example, the group found gall midges (Cecidomyiidae) in every home, even though their entire life cycle takes place outdoors. There is nothing for them to eat in a human home. Gall flies are also representative of many arthropods found in one other way: They are best seen with a microscope. A big gall fly is about 2 mm long. 
 
 Mat Bertone, NCSU 
 
 “So much of what we find in houses is incredibly tiny, and even if you're looking for it, you wouldn't be able to find it,” said Trautwein. Someone who isn’t a specialist might never see them unless they know what to look for. “I’d be crawling around and I'd see fecal specs and I go, 'Okay, there's a spider under there,'" says Bertone. "People don't know what those are. They see those little spots, but they have no idea that it's spider poop.” 
 
 Now that you are suspicious about every speck you might see in your house, here’s what the researchers didn’t find: not a single brown recluse spider or bed bug. They didn’t find very many fleas. Most of the arthropods they found were harmless, minute, accidental visitors lured in from the outdoors to a quiet death from starvation, dehydration, or cobweb spiders. 
 
 The number of bugs in our houses makes more sense when you consider that human-built spaces encompass an area as large as some natural biomes globally. But we know far more about the animals outside our houses than in them. “The finding that ‘non-pest’ species made up the majority, ... and the sheer number and prevalence of arthropod groups found highlights [our] current lack of knowledge,” says University of Liverpool biologist Crystal Frost. 
 
 Many of the insects identified in the study weren’t able to be identified to species—and some of them will probably turn out to be new species. Our homes aren't the Galapagos Islands, but they are unique environments that organisms may specialize in. We know that some fungi are found only in bathrooms and washing machines, and the same is quite likely of a few insects and spiders from this study. Carpet beetles, clothes moths, and cobweb spiders have limited abilities to disperse on their own, but we move them from place to place with our belongings. 
 
 This research is being continued across several continents, with hopes of finding patterns in our arthropod bunkmates. Their preliminary data is clear—you’ve got bugs in your house. All of you. 
 
 Keep Calm and Arthropod On 
 
 You probably weren’t freaking out about the hundreds (probably thousands) of tiny animals in your home before you read this, so why not strive to reclaim that Zen state of blissful ignorance? Even better, embrace the amazing diversity all around you. Wildlife doesn’t stop at your doorstep. It comes inside with you and lives on you. 
 
 Our homes are places of extreme environments and change. Showers go from dry to torrents of scalding water in an instant; sinks are deluged with minty alcoholic mouthwash, caustic cleaners, and hair from our grooming rituals. Humidity and temperature in ductwork change abruptly as air conditioning or heating kicks on. Anything that manages to live in this environment should get at least a little grudging admiration. 
 
 This research is just the latest in a series of papers beginning to investigate the urban environment around you. Most of the info is profoundly disturbing to people who want their homes to be immaculate. Microbial communities on our pillow cases and toilet seats are remarkably similar. Follicle mites are having sex in your facial pores right now. In the last 50 years, American basements were quietly taken over by a foreign species of camel cricket. No one noticed. It's exploration of a whole new frontier, a new environment in which we can all be participants in the science. 
 
 You are an animal, surrounded by other animals. Get. Over. It. 
 
 https://youtu.be/_WWcbIsu3V4 
 
 Bertone et al. (2016), Arthropods of the great indoors: characterizing diversity inside urban and suburban homes. 
 
 PeerJ 4:e1582; DOI 10.7717/peerj.1582 
 
 Martin et al. 2015. Evolution of the indoor biome. DOI 10.1016/j.tree.2015.02.001 
 
 Dunn et al. 2013. Home Life: Factors Structuring the Bacterial Diversity Found within and between Homes. PLoS ONE 8(5): e64133. doi:10.1371/journal.pone.0064133 
 
 Epps et al. 2014. Too big to be noticed: Cryptic invasion of Asian camel crickets in North American houses. PeerJ 2: e523; DOI 10.7717/peerj.523 ||||| Forget the rain forest—your home is brimming with bugs. More than 500 kinds of them. 
 
 Spiders, flies, beetles, ants, and book lice are among the critters detected in a new study, the first to evaluate arthropod diversity in U.S. homes. 
 
 Arthropods—a huge group that includes insects, spiders, and their relatives—have been living and evolving alongside people for millennia. (See "Why Did Thousands of Venomous Spiders Swarm a House?") 
 
 “Nobody had done a comprehensive inventory like this before, and we found far more diversity than most people would expect," says study leader Matt Bertone, an entomologist at North Carolina State University. 
 
 “That old wives’ tale that you’re never more than ten feet [three meters] away from a spider? If you’re in your home, that might be true,” Bertone says: His team found spiders in all of the homes surveyed. 
 
 Home is Where the Bugs Are 
 
 For the study, Bertone and colleagues visited 50 free-standing houses in and around Raleigh, North Carolina. 
 
 “We had two or three entomologists searching the houses, crawling on our hands and knees with flashlights and collecting anything we could find into vials,” says Bertone. The researchers collected their samples, both living and dead, using forceps, aspirators—a type of vacuum—and nets. 
 
 If You're Scared of Bugs, Don't Watch This Behind the scenes at the Smithsonian's Insect Zoo, entomologists care for a plethora of insects, including giant cockroaches, tarantulas, and even a giant 300-legged centipede. Video. 
 
 
 
 Bertone and his colleagues gathered over 10,000 specimens, representing over 300 families of arthropods, and conservatively, 579 species. Each house was home to anywhere between 32 and 211 arthropod species, according to the study, published January 19 in the journal Peer J. 
 
 In addition to the sheer number of species, the researchers were surprised at how many bugs they found in the homes. Out of more than 550 rooms sampled, only five were totally bugless. (See "7 Bug and Spider Myths Squashed.") 
 
 Although some of the species have adapted to live happily alongside humans, such as book lice, others, such as leafhoppers and gall midges, are accidental visitors. These bugs simply wander in from the outdoors and can become trapped and die, the study authors say. 
 
 Peaceful Cohabitators 
 
 There are probably even more bugs in our homes, since the researchers only collected arthropods from visible surfaces, excluding areas such as behind walls, under heavy furniture, and in drawers and cabinets, Bertone says. 
 
 But he emphasizes that we shouldn't be afraid of the bugs in our midst—the vast majority are not harmful. Typical household pests, such as German cockroaches, termites, and fleas, were only present in a few homes, the survey found. And those ubiquitous spiders found in every home are very benign—not to mention they eat pests. (Related: "What Should You Do If You Find a Spider in Your House?") 
 
 “My take-home message to the homeowners was that these things are living among you but they’re not dangerous and you won’t see them unless you really look for them,” says Bertone. “They are peacefully cohabitating with us.” 
 
 Jason Cryan, an entomologist at the North Carolina Museum of Natural Sciences, says he's "not bothered by the fact that they are finding so much arthropod diversity in our homes." 
 
 “In many cases this diversity goes unseen and unheard,” says Cryan, who was not involved in the study. 
 
 “I hope people will appreciate this natural diversity and realize that this life among us is not a health or a cleanliness concern.”
– You thought Asian camel crickets were bad. A new report in journal Peer J finds hundreds of bugs likely lurk in your home, including spiders, beetles, ants, and book lice. Scientists got down on their hands and knees and combed 50 houses in the suburbs of Raleigh, NC, picking up any bugs they found, to determine the diversity of arthropods indoors. They "found far more diversity than most people would expect," study leader Matt Bertone tells National Geographic. More specifically, they gathered 10,000 bugs from 579 species. If that doesn't freak you out, this probably will: Each home housed 100 species on average, per New Scientist, though one revealed 211 species. And less than 1% of rooms were bug-free. "That old wives' tale that you're never more than 10 feet away from a spider? If you're in your home, that might be true," Bertone says. Every home contained ants, carpet beetles, cobweb spiders, and gall midges, which "rely on things we produce or have in our homes," says Bertone. About 98% held book lice, which eat mold and mildew, reports Wired. There were even some bugs scientists suspect might be new species. Since scientists searched carpets, floorboards, and shelves, but not behind walls, under heavy furniture, or in cabinets, they say more bugs are probably hiding nearby. On the plus side, most were harmless. "The residents were really surprised and often horrified that we found so much," says Bertone. But except for the occasional cockroaches, termites, and fleas, the bugs are "not dangerous and you won't see them unless you really look for them." Just think of them as "quiet roommates," adds a co-author. (Your home's dust contains 9,000 species of microbes.)