Verified envenomations by crevice weaver spiders (genus Kukulcania): Bites are of minor expression but the spiders are commonly misidentified as medically important brown recluses (genus Loxosceles) in North America.

From southern North America, five verified bites by crevice weaver spiders, Kukulcania spp. (Filistatidae), are presented here, three of which are pediatric cases. Although the envenomation manifestations were of minimal expression, the salient aspect of this report is that Kukulcania spiders are frequently misidentified as brown recluse spiders (genus Loxosceles) which are infamous for causing serious dermonecrosis and rarely, life-threatening systemic effects. Misidentification of this relatively harmless spider as a medically important recluse when presented to a physician in an envenomation episode could lead to unwarranted and overzealous treatment such as contraindicated debridement of the affected area.

Clinical consequences of toxic envenomation by spiders.

Spider venom is being researched for its potential use in applications such as insecticides, to better understand the dynamics of neuronal ion channel physiology and as potential remedies to counter antibiotic resistant bacteria. However, spider venom is more widely known for its ability to cause deleterious reactions after toxic envenomations in humans. In this short review, the "dark" side of spider venoms is presented to provide a counterbalance to the investigations of the positive potential that venoms can or might improve our world or its understanding. The goal was to present a short primer on species having clinical consequences in humans rather than be an exhaustive review of all spiders of medical importance.

Distribution and medical aspects of Loxosceles rufescens, one of the most invasive spiders of the world (Araneae: Sicariidae).

Loxosceles rufescens is a circum-Mediterranean spider species, potentially harmful to humans. Its native area covers the Mediterranean Basin and Near East. Easily spread with transported goods, it is meanwhile an alien and invasive species to nearly all other continents and many islands. This species occurs in semi-arid steppe-like habitats, typically under stones and in cavities, which enables it to settle inside buildings when invading the synanthropic environment. This review analyses the literature of L. rufescens bites to humans (38 publications) of which only 11 publications refer to 12 verified spider bites (11% of the reported bites). Two published allegedly deadly spider bites (Thailand 2014 and Italy 2016) involve non-verified spider bites and are thus not reliable. The symptoms and therapy of these 11 verified bites are described: only five cases showed moderate systemic effects, nine cases developed necrosis, four cases needed surgical debridement, all cases healed without complications within a few weeks. In conclusion, L. rufescens is a spider species globally spread by human activity, it rarely bites humans and the bites are less harmful than often described. There is no known fatal issue.

Efficacy of Several Pesticide Products on Brown Widow Spider (Araneae: Theridiidae) Egg Sacs and Their Penetration Through the Egg Sac Silk.

Information on pesticide effects on spiders is less common than for insects; similar information for spider egg sacs is scarcer in the open literature. Spider egg sacs are typically covered with a protective silk layer. When pesticides are directly applied to egg sacs, the silk might prevent active ingredients from reaching the eggs, blocking their insecticidal effect. We investigated the impact of six water-based pesticide sprays and four oil-based aerosol products against egg sacs of brown widow spiders, Latrodectus geometricus C. L. Koch. All water-based spray products except one failed to provide significant mortality to egg sacs, resulting in successful spiderling emergence from treated egg sacs at a similar rate to untreated egg sacs. In contrast to water-based sprays, oil-based aerosols provided almost complete control, with 94-100% prevention of spiderling emergence. Penetration studies using colored pesticide products indicated that oil-based aerosols were significantly more effective in penetrating egg sac silk than were the water-based sprays, delivering the active ingredients on most (>99%) of the eggs inside the sac. The ability of pesticides to penetrate spider egg sac silk and deliver lethal doses of active ingredients to the eggs is discussed in relation to the chemical nature of egg sac silk proteins. Our study suggests that pest management procedures primarily relying on perimeter application of water-based sprays might not provide satisfactory control of brown widow spider eggs. Determination of the most effective active ingredients and carrier characteristics warrant further research to provide more effective control options for spider egg sacs.

Establishment of the Brown Widow Spider (Araneae: Theridiidae) and Infestation of its Egg Sacs by a Parasitoid, Philolema latrodecti (Hymenoptera: Eurytomidae), in French Polynesia and the Cook Islands.

This paper presents two newly established species for French Polynesia: the invasive brown widow spider, Latrodectus geometricus C. L. Koch, and its potential biocontrol agent, the parasitoid wasp, Philolema latrodecti (Fullaway). The brown widow spider was recorded from the island of Moorea in 2006 and, since that discovery, the occurrence of this species has expanded to two of the five archipelagos of French Polynesia including the main island of Tahiti and four of the Cook Islands. Although the tropical climate contributes to the establishment of L. geometricus, a biotic factor, P. latrodecti, may restrain population from demographic explosion. This eurytomid wasp is present in French Polynesia and is a parasitoid that has been used in biological control of the southern black widow Latrodectus mactans (F.) in Hawaii. This wasp could become a significant limiting factor for L. geometricus distribution on these islands, as it was found in 31% of the Tahitian brown widow spider egg sacs that were dissected. However, thus far, the wasp was only found on Tahiti in association with the brown widow spider. Although the brown widow is generally considered to be less toxic than its black widow relatives, it remains of medical concern in French Polynesia because reactions to its bites can, at times, be severe. The spider remains of public concern because it is a novel species; it has the word widow in its name and dark morphs are mistaken as black widows.

Verified spider bites in Oregon (USA) with the intent to assess hobo spider venom toxicity.

This study compiled 33 verified spider bites from the state of Oregon (USA). The initial goal was to amass a series of bites by the hobo spider to assess whether it possesses toxic venom, a supposition which is currently in a contested state. None of the 33 bites from several spider species developed significant medical symptoms nor did dermonecrosis occur. The most common biters were the yellow sac spider, Cheiracanthium mildei (N = 10) and orb-weavers of the genus Araneus (N = 6). There were 10 bites from three genera of funnel web spiders of the family Agelenidae including one hobo spider bite and one from the congeneric giant house spider which is readily confused as a hobo spider. The hobo spider bite resulted in pain, redness, twitching in the calf muscle and resolved in 12 h. Also generated from this study were possibly the first records of bites from spiders of the genera Callobius (Amaurobiidae) and Antrodiaetus (Antrodiaetidae), both with minor manifestations.

Distribution of the brown recluse spider (Araneae: Sicariidae) in Illinois and Iowa.

The medical importance of the brown recluse spider, Loxosceles reclusa Gertsch and Mulaik, is well known, but there is a need for more accurate information about the distribution of the spider in North America. We gathered information via an Internet offer to identify spiders in Illinois and Iowa that were thought to be brown recluses. We also mined brown recluse locality information from other agencies that kept such records. In Iowa, the brown recluse is unknown from its northern counties and rare in southern counties. In Illinois, brown recluse spiders are common in the southern portion of the state and dwindle to almost nonexistence in a transition to the northern counties. Although there were a few finds in the Chicago, IL area and its suburbs, these are surmised to be human-transported specimens and not part of naturally occurring populations. Considering the great human population density and paucity of brown recluses in the Chicago area, medical personnel therein should obtain patient geographic information and be conservative when diagnosing loxoscelism in comparison with southern Illinois, where the spiders are plentiful and bites are more likely.

Exposure of Brown Recluse and Brown Widow Spiders (Araneae: Sicariidae, Theridiidae) to a Commercial Sulfuryl Fluoride Fumigation.

The body of pesticide research on spiders is sparse with most studies using topical or residual applications to assess efficacy. Data on the effects of fumigation on spider survivorship are scarce in the scientific literature. In this study, we exposed adult male and female brown recluse spiders, Loxosceles reclusa Gertsch & Mulaik, and female brown widow spiders, Latrodectus geometricus C. L. Koch, to a commercial fumigation event using sulfuryl fluoride directed at termite control. General consensus from the pest control industry is that fumigation is not always effective for control of spiders for a variety of reasons, including insufficient fumigant dosage, particularly, for contents of egg sacs that require a higher fumigant dosage for control. We demonstrated that a sulfuryl fluoride fumigation with an accumulated dosage of 162 oz-h per 1,000 ft(3) at 21°C over 25 h (≈1.7 × the drywood termite dosage) directed at termites was sufficient to kill adult brown recluse and brown widow spiders. The effectiveness of commercial fumigation practices to control spiders, and particularly their egg sacs, warrants further study.

Spiders (Araneae) Found in Bananas and Other International Cargo Submitted to North American Arachnologists for Identification.

Spiders found in international cargo brought into North America are sometimes submitted to arachnologists for identification. Often, these spiders are presumed to be of medical importance because of size or a submitter's familiarity with a toxic spider genus from the continent of origin. Starting in 2006, requests were made for spiders found in international cargo brought into North America, in addition to the specimens from similar cargo shipments already in our museum collections. This was an ad hoc study that allowed us to focus on spiders of concern to the discoverer. We identified 135 spiders found in international cargo. A key for the most common species is provided. The most frequently submitted spiders were the pantropical huntsman spider, Heteropoda venatoria (L.) (Sparassidae), and the redfaced banana spider, Cupiennius chiapanensis Medina Soriano (Ctenidae). Spiders of medical importance were rare. The most common cargo from which spiders were submitted was bananas with most specimens coming from Central America, Ecuador, or Colombia. Lack of experience with nonnative fauna caused several experienced American arachnologists to misidentify harmless ctenid spiders (C. chiapanensis, spotlegged banana spider, Cupiennius getazi Simon) as highly toxic Phoneutria spiders. These misidentifications could have led to costly, unwarranted prophylactic eradication measures, unnecessary employee health education, heightened employee anxiety and spoilage when perishable goods are left unloaded due to safety concerns.

Spider envenomation in North America.

In North America, spider envenomation is perceived to be a greater threat than in actuality; however, it still is a valid source of morbidity and, very rarely, mortality. Only 2 groups (widows, recluses) are medically important on this continent. Widow bites affect the neuromuscular junction, have minor dermatologic expression, and are treated with analgesics and antivenom. Recluse bites vary from mild, self-limiting rashes to extensive dermonecrosis. Recent awareness of methicillin-resistant Staphylococcus aureus as a ubiquitous cause of skin injury that is often mistaken as attributable to recluse bites has questioned the credence of spiders being the cause of idiopathic wounds.

The prevalence of brown widow and black widow spiders (Araneae: Theridiidae) in urban southern California.

The brown widow spider, Latrodectus geometricus C. L. Koch, has become newly established in southern California during the first decade of the 21st century. Brown widows and egg sacs were collected within the urban Los Angeles Basin using timed searches. We also collected and compared the abundance and distribution of the native western black widow spider, Latrodectus hesperus Chamberlin & Ivie, to brown widows. Brown widows were very common around urban structures especially outside homes, in parks, under playground equipment, in plant nurseries and landscaping areas, greatly outnumbering native western black widows, and were very rare or nonexistent in garages, agricultural crops, and natural areas. Western black widows predominated in xeric habitats and were less prevalent around homes. Neither species was found in the living space of homes. In southern California, envenomation risk exists because brown widows are now common in urban areas and the spiders hide where people place their fingers and exert pressure to move objects (e.g., under the curled lip of potted plants, in the recessed handle of plastic trash bins). Nonetheless, brown widow spider bites are less toxic than those of native western black widow spiders and, hence, if they are displacing black widows, overall widow envenomation risk may actually be lower than before brown widow establishment.

Envenomation by spiders of the genus Hololena (Araneae: Agelenidae).

Three verified bites from Hololena spiders (Family Agelenidae) are presented here. Two male victims, each over 100 kg weight (bitten by female spiders), experienced headaches and 4-h episodes of vomiting. A female bite victim (bitten by a male spider) experienced minor reaction. None sought medical attention; symptoms resolved in a few days. Although these incidents were not serious, reactions in the male victims were more dynamic than usual generic spider bites (minor edema, minor erythema).

Seasonality of brown recluse spiders, Loxosceles reclusa, submitted by the general public: implications for physicians regarding loxoscelism diagnoses.

Many medically important animals exhibit fluctuating seasonal abundance such that risk from envenomation or disease is not constant throughout the year. As indicated by homeowner submissions, brown recluse spiders, Loxosceles reclusa, show seasonal peaks of activity during summer and paucity in winter. This information should be incorporated as part of the diagnostic algorithm for physicians when considering the probability of loxoscelism in endemic Loxosceles areas especially if a skin lesion occurs when spiders are scarce.

Scavenging by spiders (Araneae) and its relationship to pest management of the brown recluse spider.

Experiments reported in Sandidge (2003; Nature 426: 30) indicated that the brown recluse spider, Loxosceles reclusa Gertsch & Mulaik, preferred to scavenge dead prey over live prey and that the spiders were not detrimentally affected when fed insecticide-killed crickets. Extrapolations made in subsequent media coverage disseminating the results of this research made counter-intuitive statements that pesticide treatment in houses would increase brown recluse populations in homes. This information was presented as if the scavenging behavior was specialized in the brown recluse; however, it was more likely that this behavior has not been well studied in other species. To provide a comparison, the current laboratory study examined the likelihood of non-Loxosceles spiders to scavenge dead prey. Of 100 non-Loxosceles spiders that were tested (from 11 families, 24 genera, and at least 29 species from a variety of spider hunting guilds), 99 scavenged dead crickets when offered in petri dishes. Some of the spiders were webspinners in which real-world scavenging of dead prey is virtually impossible, yet they scavenge when given the opportunity. Therefore, scavenging is a flexible opportunistic predatory behavior that is spread across a variety of taxa and is not a unique behavior in brown recluses. These findings are discussed in relation to pest management practices.

Cobweb management and control of the spider Holocnemus pluchei (Araneae: Pholcidae) on buildings.

The spider Holocnemus pluchei (Scopoli) (Araneae: Pholcidae) is a nonnative species commonly found in the southwestern United States. In urban areas around homes and other structures, it is often the dominant spider species on outside surfaces; requests for control of spiders and their cobwebs are common for the commercial pest management industry. We tested two physical (brushing and vacuuming) and two low-impact chemical (permethrin and botanical insecticide) spray control methods for H. pluchei on outbuildings on the University of California-Riverside campus. Forty sites containing at least two H. pluchei spiders along a 5-m section of eave or overhang were chosen for treatment. Treatment was applied within 2 d of a pretreatment census. The number of spiders per section was counted at 2, 4, 8, 12, 16, and 52 wk posttreatment. Untreated sections showed an increase in spiders through summer and a decrease in autumn. Sites treated with permethrin significantly reduced spiders >95% and had strong residual effect throughout the remainder of the sampling period. Compared with untreated controls, the three other treatments did not significantly reduce spiders; these three were similar throughout the season and were intermediate between untreated and permethrin-treated sites. In comparison with the before and 2-wk posttreatments, spiders at the untreated sites showed no difference in body sizes, whereas those in the nonpermethrin treatments showed a decrease, indicating that larger spiders were eliminated. We also tested H. pluchei spiders in the laboratory against the two insecticides used in the field studies to determine the minimum lethal concentrations for controlling H. pluchei.

Tracking a medically important spider: climate change, ecological niche modeling, and the brown recluse (Loxosceles reclusa).

Most spiders use venom to paralyze their prey and are commonly feared for their potential to cause injury to humans. In North America, one species in particular, Loxosceles reclusa (brown recluse spider, Sicariidae), causes the majority of necrotic wounds induced by the Araneae. However, its distributional limitations are poorly understood and, as a result, medical professionals routinely misdiagnose brown recluse bites outside endemic areas, confusing putative spider bites for other serious conditions. To address the issue of brown recluse distribution, we employ ecological niche modeling to investigate the present and future distributional potential of this species. We delineate range boundaries and demonstrate that under future climate change scenarios, the spider's distribution may expand northward, invading previously unaffected regions of the USA. At present, the spider's range is centered in the USA, from Kansas east to Kentucky and from southern Iowa south to Louisiana. Newly influenced areas may include parts of Nebraska, Minnesota, Wisconsin, Michigan, South Dakota, Ohio, and Pennsylvania. These results illustrate a potential negative consequence of climate change on humans and will aid medical professionals in proper bite identification/treatment, potentially reducing bite misdiagnoses.