Bioacoustics of Pholcidae

Ninetinae biology: a summary This paper concludes a series of recent papers that revised most known ninetine genera ( Huber et al. 2023 a , 2023 b, 2023c , 2024 a , 2024 b, 2024c ; Huber & Meng 2025 ). We take this opportunity to summarize current knowledge about this previously most enigmatic subfamily of Pholcidae . Figure 86 gives an overview of the genera included in the subfamily, their relationships, and their distribution. However, here we focus on some contrasting aspects united in this subfamily. In some respects, Ninetinae is a very homogeneous group, for example regarding ecology and general morphology. In other respects, Ninetinae exhibit substantial variation, as for example in sexual morphology and sperm morphology (and karyology, see above). Most Ninetinae occupy very similar ecoregions, ranging from xeric shrubland to dry forests. They are rarely found in more humid environments such as the Southern Andean Yungas, and they are conspicuously absent from moist forests, which are otherwise the ecoregions with the highest species richness in Pholcidae ( Huber & Rheims 2011 ; Castanheira et al. 2016 ). Ninetinae also occupy a very limited number of different microhabitats. The most promising methods to find Ninetinae are turning stones and rocks, beating dead branches and cacti lying on the ground, and sifting dry leaf litter. Upon disturbance, the spiders usually run quickly; the vibrating, bouncing, or whirling that is so typical of long-legged relatives (e.g., Jackson et al. 1990 , 1992 , 1993) is precluded by their short legs. Webs have never been observed in the field, but representatives of several genera have been observed to build and to rest on small sheets of silk in collecting vials; except for their size, these webs look fundamentally very similar to the typical Pholcidae domed sheet web supported by some scaffolding lines (cf. Eberhard 1992 ). Related to this ecological homogeneity is a conservative general morphology. Ninetinae are usually small spiders (body length mostly 1–2 mm ) with short legs, domed carapace without or with a very shallow thoracic groove, and globular abdomen. The short leg length probably affects a range of other characters that are characteristic for Ninetinae , such as (1) the very distal position of the retrolateral trichobothrium on the leg tibia (usually at ~50–70% of tibia length; in most other pholcids at 1–40%); (2) the flattened rather than round egg-sac (many Ninetinae would not be able to run carrying an egg sac under the prosoma that is higher than one egg diameter); and (3) the low number of comb hairs on the prolateral side of tarsus 4 (only one or two). Beyond absolute leg-length, also leg proportions are unusual for Pholcidae but similar among Ninetinae : the fourth leg is usually longer than the first leg; the metatarsus is barely longer or even shorter than the tibia; the first leg is barely longer than the second leg; and ‘leg slenderness’ (measured as tibia 1 length / diameter) is usually at ~7–15 (in other pholcids mostly ~20–120). Ninetinae occasionally enter caves as is generally true for many species of Pholcidae (reviewed in Huber 2018b ), but no troglomorphisms are known in the subfamily. Thus, pigmentation is also homogeneous within the subfamily, with little color except for shades of ochre and brown, and with very little color pattern. Finally, as expected from the similar ecology and webs, tarsal tip morphology (claws and setae) is also very homogeneous among Ninetinae . This morphological conservatism extends to traits that are not easily explained by ecology alone. (1) All Ninetinae share a very similar eye pattern: the AME that have repeatedly been lost in other subfamilies are always present and relatively big. (2) The spinneret and spigot morphology is almost identical across the entire subfamily: except for Ibotyporanga , all Ninetinae have the identical set of ALS spigots, even with remarkably consistent shapes and relative sizes of the individual spigots. (3) All Ninetinae except for Tolteca Huber, 2000 have retained male cheliceral stridulation, which has repeatedly been lost in other subfamilies. Ninetinae females, on the other hand, have apparently never developed any kind of stridulation; such female stridulation (prosoma-abdomen) has evolved at least ten times in other subfamilies ( Huber 2021 ). (4) All Ninetinae have very short hairs (“short vertical hairs”) on the anterior (or rarely all) leg tibiae that are sexually dimorphic (males only, see below). (5) All Ninetinae share capsulate tarsal organs with a very small opening (~1–2 µm); exposed tarsal organs have repeatedly evolved in other subfamilies but not in Ninetinae . In contrast to this, considerable variation occurs in morphological characters related to sexual biology, far beyond the ubiquitous phenomenon of species-specific genitalia. (1) The male chelicerae are usually set with a pair of apophyses; in Ibotyporanga , these apophyses are fused to a single median process; in Galapa and in certain species of Nerudia Huber, 2000 , Ninetis Simon, 1890 , and Kambiwa , they are lost. (2) The male cheliceral fangs are usually unmodified, but in Galapa they carry a pair of processes. (3) The male clypeus is unmodified in most Ninetinae , but provided with a median process in Pinoquio barauna ( Huber & Carvalho, 2019 ) and Guaranita dobby Torres et al. , 2016 , with a notch in Ibotyporanga , and with modified hairs in Galapa murphyi Huber, 2024 . (4) Male sternum humps are present in some genera but absent in others, with no apparent phylogenetic pattern. (5) The male gonopore of most Ninetinae is provided with four epiandrous spigots, usually arranged in two pairs; however, several genera seem to contain both species with and without epiandrous spigots ( Tolteca , Ninetis , Sertana , Galapa , Kambiwa ). This suggests multiple convergent losses, similar to other Pholcidae subfamilies. (6) The epigynal plate is usually simple, with little sculpture, but in Ibotyporanga and some species of Ninetis , it is provided with a median pocket, presumably with different functions in the two genera. (7) Females of Tolteca are provided with a unique knob between the epigynum and the pedicel; its function is unknown. (8) Glandular pore plates in the female internal genitalia are present in Ibotyporanga , similar to most other Pholcidae , but strongly reduced or absent in all other Ninetinae . (9) Further details of the female internal genitalia are poorly explored, but long tubes have apparently evolved repeatedly in Ibotyporanga , Gertschiola Brignoli, 1981 , and Kambiwa . In all three cases, this seems correlated with an elongation of certain male palpal sclerites ( Izquierdo et al. 2023 ; Huber et al. 2024c , present paper). Sperm ultrastructure in Pholcidae has been summarized in Dederichs et al. (2022) , with additional data on the ninetine genus Papiamenta Huber, 2000 in Huber et al. (2024b) . The most intriguing variation among Ninetinae concerns the sperm transfer form (cleistospermia vs synspermia). This finding is difficult to interpret in evolutionary terms. If the synspermia of Ninetinae (confirmed in Gertschiola , Nerudia , Guaranita , Galapa , Kambiwa ) are retained from the ancestral Synspermiata, then the cleistospermia in other Pholcidae must have evolved at least five times independently (Pholcinae + Smeringopinae; Caipirinae; Arteminae; Modisiminae; Papiamenta + Tolteca + Pholcophora ) (based on the cladogram in Meng et al . 2026 ). Alternatively, the synspermia in Ninetinae might represent a reversal to the original mode of Synspermiata sperm transfer; this scenario requires only two evolutionary steps within Synspermiata. Sexual dimorphisms have evolved many times independently in Pholcidae , also within Ninetinae (reviewed in Huber 2021 ; updated for Ninetinae in Huber et al. 2023c ). According to our current understanding of Ninetinae phylogeny, sexual dimorphisms have evolved approximately nine times in this subfamily: (#1) Modified male cheliceral fangs originated in the ancestor of Galapa . (#2) All Ninetinae except Tolteca have sexually dimorphic cheliceral stridulation: present in males, absent in females. However, it is not clear if this is plesiomorphic or derived. (#3–6) Clypeus modifications have evolved at least four times in Ninetinae : in Pinoquio barauna , Guaranita dobby , Galapa murphyi , and in the ancestor of Ibotyporanga . Subtle dimorphisms (male clypeus slightly more protruding and with sclerotized rim) occur in additional taxa and may represent one or more further origins. (#7) A pair of anterior humps on the male sternum occur in several ninetine genera, but it is unclear if this is the result of multiple origins or losses. Such humps are absent in the sister group of Ninetinae , suggesting at least one origin (in the ancestor of Ninetinae ). (#8) Very short hairs (~15–20 µm) that remind of chemoreceptors but are unbranched and restricted to (or occur in much higher densities on) male legs (the so-called “vertical hairs”) seem to occur in all Ninetinae , but not in the sister group of Ninetinae . (#9) Raised male palpal tarsal organs may have evolved in the ancestor of Ninetinae . However, they also occur in Priscula and might thus not represent an independent origin for Ninetinae .

Diagnosis. Small to medium-sized pholcids (carapace width 0.4–2.8), usually with relatively long legs (tibia 1 / carapace width usually> 3; shorter in Aucana Huber, 2000 ; Changminia Yao and Li, 2022 ; Nita Huber and El Hennawy, 2007 ; and in most species of Chisosa Huber, 2000 ), usually with eight eyes ( AME very rarely absent, e. g. in Pholcitrichocyclus watta (Huber, 2001 )) . Distinguished from most other subfamilies by the combination of (1) presence of cheliceral stridulation (absent in Caipirinae subfam. nov. , Modisiminae, Priscula Simon, 1893 ; most Pholcinae, southern clade of Smeringopinae; present in Artema Walckenaer 1837 ; Ninetinae; northern clade of Smeringopinae) and (2) strongly widened femur of male palp (similar in Artema , Priscula ; certain species of Mesabolivar González-Sponga, 1998 ); Artema is distinguished from Physocyclinae by series of unique conical setae on male chelicerae (never present in Physocyclinae ). Caipirinae is further distinguished from Physocyclinae by pair of epigynal pockets (never present in Physocyclinae ).