Although descended from orb weavers, spiders in the family Theridiidae spin cobwebs whose sticky prey capture gumfoot lines extend from a silk tangle to a surface below. When a crawling insect contacts glue droplets at the bottom of a gumfoot line, the line\'s weak pyriform anchor releases, causing the taut line to contract, pulling the insect from the surface and making its struggles to escape ineffective. To determine if this change in prey capture biomechanics was accompanied by a change in the material properties of theridiid glue, we characterized the elastic modulus and toughness of the glue droplet proteins of four theridiid species at 20-90 % relative humidity and compared their properties with those of 13 orb weaving species in the families Tetragnathidae and Araneidae. Compared to orb weavers, theridiid glue proteins had low extensions per protein volume and low elastic modulus and toughness values. These differences are likely explained by the loss of tension on a gumfoot line when its anchor fails, which may prioritize glue droplet adhesion rather than extension. Similarities in theridiid glue droplet properties did not reflect these species\' evolutionary relationships. Instead, they appear associated with differences in web architecture. Two species that had stiffer gumfoot support lines and longer and more closely spaced gumfoot lines also had stiffer glue proteins. These lines may store more energy, and, when their anchors release, require stiffer glue to resist the more forceful upward thrust of a prey. STATEMENT OF SIGNIFICANCE: When a crawling insect contacts glue droplets on a theridiid cobweb\'s gumfoot line, this taut line\'s anchor fails and the insect is hoisted upward, rendering its struggles to escape ineffective. This strategy contrasts with that of orb weaving ancestors, which rely on more closely spaced prey capture threads to intercept and retain flying insects. A comparison of the elastic modulus and toughness of gumfoot and orb web glue proteins shows that this change in prey capture biomechanics is associated with reductions in the stiffness and toughness of cobweb glue. Unlike orb web capture threads, whose droplets extend in a coordinated fashion to sum adhesive forces, gumfoot lines become untethered, which prioritizes glue droplet adhesive contact over glue droplet extension.

Female black widow spiders, Latrodectus hesperus Chamberlin and Ivie (Araneae: Theridiidae), are solitary predators of arthropods with no tolerance for intruders on the webs. In California, L. hesperus are found in urban and agricultural settings and can be a phytosanitary pest in fresh produce. Spatial separation of L. hesperus webs could be determined by seasonal population densities, with territorial competition expected under high densities in the environment. However, little is known about female-female communication behaviors in this species. In 1-hr laboratory observations, displays of female-female rivalry included production of vibrational signals in a majority (20 of 30) of trials. The number of signals produced by both females was highest during the initial 10 min of trials, with signaling rate (time interval between signals) peaking during the 40-50 min observation period. The overall ratio of signals produced by the resident female and the introduced female was about 5:1, with the number of signals produced by the resident female higher than the number of signals produced by the introduced female. Analysis of rivalry signals showed a peak in magnitude (about 0.4 m/s) ranging from 6 to 23 Hz and smaller peaks at about 29, 38, and 47 Hz. Collectively, these results demonstrate that female L. hesperus exhibit territorial rivalry and that female-female rivalry is mediated by emission of vibrational signals through the web. Understanding the mechanisms of intraspecific competition in L. hesperus is required for elucidating interspecific interactions in the environment and may lead to development of novel methods to prevent spiders from colonizing crops.

Mating systems, with varying female mating rates occurring with the same partner (monandry) or with multiple mates (polyandry), can have far reaching consequences for population viability and the rate of gene flow. Here, we investigate the mating rates of the common house spider Parasteatoda tepidariorum (Theridiidae), an emerging model for genetic studies, with yet undescribed reproductive behavior. It is hypothesized that spiders belonging to this family have low re-mating rates. We paired females twice with the same male (monandry) or with different males (polyandry), and recorded behaviors, mating success and fitness resulting from single- and double-matings, either monandrous or polyandrous. Despite the study being explorative in nature, we predict successful matings to be more frequent during first encounters, to reduce female risk of remaining unmated. For re-mating to be adaptive, we expect higher fitness of double-mated females, and polyandrous females to experience highest mating success and fitness if reproductive gains are achieved by mating with multiple partners. We show that the majority of the females did not mate, and those that did mated only once, not necessarily on their first encounter. The likelihood of re-mating did not differ between monandrous and polyandrous encounters and female mating experience (mated once, twice monandrous, twice polyandrous) did not affect fitness, indicated by similar offspring production. Female twanging of the web leads to successful matings suggesting female behavioral receptivity. Cannibalism rates were low and mostly occurred pre-copulatory. We discuss how the species ecology, with potentially high mating costs for males and limited female receptivity, may shape a mating system with low mating rates.

We report a case of envenomation by Steatoda borealis (Hentz, 1850) in Connecticut in late spring 2021. The bitten subject was a 60-yr-old female Caucasian. The bite occurred upon disturbing some books in her basement. She reported a painful stinging bite on her finger followed by the formation of an erythematous macule at the site of the bite which was gone the next day. There was no sign of necrosis. The spider was recovered directly at that time. The victim reported that later that night she experienced heart palpitations. This is the first report of envenomation by S. borealis, a common spider in Connecticut.

Spiders are one of the most important orders of Arachnida comprising more than 48,000 species in the world. Except for families Uloboridae and Holarchaeidae, all others are classified as the venomous spider. However, only about 200 species are medically relevant and cause public health problems or even death. In Iran, there are 51 families and 763 species of spiders, of which the families, Theridiidae and Sicariidae are dangerous for the human being, and the first one is more prevalent. The Latrodectus is considered one of the most poisonous spiders in the world and Iran. This genus has five species in Iran, among which Latrodectus tredecimguttatus (black widow spider or “Dolmak”) is considered one of the most poisonous spiders in Iran. Therefore, this study aimed to investigate this species in the Northwest of Iran (West Azerbaijan, East Azerbaijan, and Ardabil provinces, Iran). Spatial distribution maps were prepared using GIS 9.4. In the current study, five adult female spiders were collected from Germi and Ardabil cities (Ardabil Province), Ahar County (East Azerbaijan province), and Urmia city (West Azerbaijan province) of Iran. These species were first observed in Ardabil province, Iran. Therefore, the presence of Latrodectus species under the rocks in wheat farms in this corner of Iran may be a threat to farms and visitors. People in these areas should wear gloves and avoid any activity that disturbs the spiders and make them aggressive.

The spiders of Theridiidae\'s family display a peculiar behaviour when they hunt extremely large prey. They lift the quarry, making it unable to escape, by attaching pre-tensioned silk threads to it. In this work, we analysed for the first time in the laboratory the lifting hunting mechanism and, in order to quantify the phenomenon, we applied the lifting mechanics theory. The comparison between the experiments and the theory suggests that, during the process, spiders do not stretch the silk too much by keeping it in the linear elastic regime. We thus report here further evidence for the strong role of silk in spiders\' evolution, especially how spiders can stretch and use it as an external tool to overcome their muscles\' limits and capture prey with large mass, e.g. 50 times the spider\'s mass.

Prey species rarely seek out and dismantle traps constructed by their predators. In the current study, we report an instance of targeted trap destruction by an invertebrate and a novel context for rescue behavior. We found that foragers of the granivorous desert ant (Veromessor pergandei) identify and cooperatively dismantle spiderwebs (Araneae: Theridiidae, Steatoda spp., and Asagena sp.) During group foraging, workers ensnared in webs are recovered by sisters, which transport them to the nest and groom away their silk bindings. The presence of an ensnared nestmate and chemical alarm signal significantly increased the probability of web removal and nestmate retrieval. A subset of larger-bodied foragers participated in web removal, and 6.3% became tangled or were captured by spiders. Most animals that perform rescue behavior live in small groups, but V. pergandei colonies include tens of thousands of short-lived workers. To maintain their size, large colonies must collect enough seeds to produce 650 new ants each day. We hypothesize that the removal of spiderwebs allows for an unimpeded income of seeds on a single foraging path during a brief daily temperature window. Despite the cost to individuals, webs are recognized and removed only when workers are captured in them.

Orb-web weaving spiders and their relatives use multiple types of task-specific silks. The majority of spider silk studies have focused on the ultra-tough dragline silk synthesized in major ampullate glands, but other silk types have impressive material properties. For instance, minor ampullate silks of orb-web weaving spiders are as tough as draglines, due to their higher extensibility despite lower strength. Differences in material properties between silk types result from differences in their component proteins, particularly members of the spidroin (spider fibroin) gene family. However, the extent to which variation in material properties within a single silk type can be explained by variation in spidroin sequences is unknown. Here, we compare the minor ampullate spidroins (MiSp) of orb-weavers and cobweb weavers. Orb-web weavers use minor ampullate silk to form the auxiliary spiral of the orb-web while cobweb weavers use it to wrap prey, suggesting that selection pressures on minor ampullate spidroins (MiSp) may differ between the two groups.
We report complete or nearly complete MiSp sequences from five cobweb weaving spider species and measure material properties of minor ampullate silks in a subset of these species. We also compare MiSp sequences and silk properties of our cobweb weavers to published data for orb-web weavers. We demonstrate that all our cobweb weavers possess multiple MiSp loci and that one locus is more highly expressed in at least two species. We also find that the proportion of β-spiral-forming amino acid motifs in MiSp positively correlates with minor ampullate silk extensibility across orb-web and cobweb weavers.
MiSp sequences vary dramatically within and among spider species, and have likely been subject to multiple rounds of gene duplication and concerted evolution, which have contributed to the diverse material properties of minor ampullate silks. Our sequences also provide templates for recombinant silk proteins with tailored properties.

\"Nesticus\" citrinus, a species originally placed in Theridion is redescribed based on the syntype series composed by 7 females and a lectotype is designated. All syntypes have broken emboli in their epigynes. Taxonomic position of \"Nesticus\" citrinus is briefly discussed and its belonging to Nesticidae is doubted.

The Caribbean island biota is characterized by high levels of endemism, the result of an interplay between colonization opportunities on islands and effective oceanic barriers among them. A relatively small percentage of the biota is represented by \'widespread species,\' presumably taxa for which oceanic barriers are ineffective. Few studies have explored in detail the genetic structure of widespread Caribbean taxa. The cobweb spider Spintharus flavidus Hentz, 1850 (Theridiidae) is one of two described Spintharus species and is unique in being widely distributed from northern N. America to Brazil and throughout the Caribbean. As a taxonomic hypothesis, Spintharus \"flavidus\" predicts maintenance of gene flow among Caribbean islands, a prediction that seems contradicted by known S. flavidus biology, which suggests limited dispersal ability. As part of an extensive survey of Caribbean arachnids (project CarBio), we conducted the first molecular phylogenetic analysis of S. flavidus with the primary goal of testing the \'widespread species\' hypothesis. Our results, while limited to three molecular loci, reject the hypothesis of a single widespread species. Instead this lineage seems to represent a radiation with at least 16 species in the Caribbean region. Nearly all are short range endemics with several distinct mainland groups and others are single island endemics. While limited taxon sampling, with a single specimen from S. America, constrains what we can infer about the biogeographical history of the lineage, clear patterns still emerge. Consistent with limited overwater dispersal, we find evidence for a single colonization of the Caribbean about 30 million years ago, coinciding with the timing of the GAARLandia landbridge hypothesis. In sum, S. \"flavidus\" is not a single species capable of frequent overwater dispersal, but rather a 30 my old radiation of single island endemics that provides preliminary support for a complex and contested geological hypothesis.