Eight cobweb spider species from China building detritus-based, bell-shaped retreats (Araneae, Theridiidae)

Abstract Eight cobweb spider species building a detritus-based, bell-shaped retreat from China are reported in the current paper, including five new Campanicola species and three known species: Campanicolaanguilliformis Li & Liu, sp. nov., Campanicolafalciformis Li & Liu, sp. nov., Campanicolaheteroidea Li & Liu, sp. nov., Campanicolatauricornis Li & Liu, sp. nov., Campanicolavolubilis Li & Liu, sp. nov., Campanicolacampanulata (Chen, 1993), Campanicolaferrumequina (Bösenberg & Strand, 1906), and Parasteatodaducta (Zhu, 1998). Among them, the male of Parasteatodaducta (Zhu, 1998) is described for the first time. We provide photographs of all species and descriptions for new species in the current paper. The type of bell-shaped retreat is rare in theridiid, and found only in four related genera. A natural next step upon completing this taxonomic study would be to analyse and understand the evolution of the retreat and related traits.

In the past three years, a series of surveys on Chinese theridiid spiders were conducted by colleagues of Hubei University in China and yielded numerous new species. This is our first paper on Chinese cobweb spiders with the aim to describe the species building bell-shaped retreats including seven Campanicola species and one Parasteatoda species.

Materials and methods
All specimens were kept in 100% ethanol and examined with an Olympus SZX16 stereomicroscope. Further details were studied under an Olympus BX51 compound microscope. Male and female genitalia were examined and illustrated after dissection. Epigynes were cleaned by Proteinase K solution. Male left palps and female epigynes were imaged with an Olympus BX51 compound microscope in ethanol and in Arabic gum. For SEM, specimens were treated according to Agnarsson (2004). Male palps were cleaned ultrasonically for 1 minute, transferred to 100% ethanol overnight, then air-dried. Palps were glued to round-headed rivets using conductive adhesive, then sputter coated and imaged by a field emission scanning electron microscope (FE-SEM JSM7100F, JEOL, JP). Spider body photos were obtained using a Leica 205C digital microscope. All images were assembled using Helicon Focus image stacking software. All measurements were obtained using a Leica 205C digital microscope and given in millimeters. Eye diameters were taken at the widest point. Leg lengths are given as: total length (femur, patella, tibia, metatarsus, tarsus Diagnosis. Campanicola is similar to some Achaearanea, Cryptachaea, Parasteatoda in building a detritus-based and bell-shaped retreat, but can be distinguished morphologically from Achaearanea by the cymbium with cymbial hood and without a distal projection in Campanicola, but with a cymbial hook and large distal projections in Achaearanea; from Cryptachaea by the cymbium not extending beyond the alveolus, the tegulum depressed and the copulatory ducts long in Campanicola, but the cymbium extending beyond alveolus, the tegulum spherical and the copulatory ducts short in Cryptachaea; from Parasteatoda by the conductor tip curved dorsally, the embolus and the copulatory ducts thin and the atrium small in Campanicola, but the conductor tip curved ventrally, the embolus and the copulatory ducts thick, the atrium large in Parasteatoda (Yoshida 2008(Yoshida , 2015Vanuytven 2021).

Campanicola ferrumequina (Bösenberg & Strand, 1906) Figs 4-6, 15, 16
Theridion ferrum-equinum Bösenberg & Strand, 1906: 139, pl. 12    Description. See Zhu (1998) and Yoshida (2000). Distribution. China (Hunan, Fujian, Sichuan, Hainan), Korea, Japan (Fig. 16). Diagnosis. This new species is similar to C. ferrumequina, C. tauricornis sp. nov. and C. volubilis sp. nov. in having spherical spermathecae, and long and looped copulatory ducts, but can be distinguished from them by the direction of the copulatory duct: it starts from the middle and anterior part of the atrium, extends posteriorly, then curves several times and enters the spermathecae laterally and ventrally in C. anguilliformis sp. nov. (Fig. 7E-H); it starts from the lateral and anterior part of the atrium, extends anteriorly, then curves several times and enters the spermathecae laterally and dorsally in C. ferrumequina (Fig. 4E-H); it starts from the lateral and anterior part of the atrium, extends anteriorly, then curves several times and enters the spermathecae laterally and ventrally in C. tauricornis sp. nov. and C. volubilis sp. nov. (Figs 10D-G, 11D-G).

Campanicola anguilliformis
Etymology. The specific name is derived from the Latin adjective anguilliformis, meaning eel-like, referring to the eel-like copulatory ducts; adjective.
Distribution. China (Sichuan) (Fig. 16). Diagnosis. This new species can be distinguished from other Campanicola species, in the female, by the position of the copulatory pores: located on the lateral and posterior part of atrium in this new species while located anteriorly in other Campanicola species; and the relative position of the copulatory ducts to the spermathecae: partial copulatory ducts overlap the posterior-ventral half of the spermathacea in this new species (Fig. 8E, G), but nearly all copulatory ducts are below the spermathecae in other Campanicola species.

Campanicola falciformis
Etymology. The specific name is derived from the Latin adjective falciformis, meaning doubly falcate, referring to the falcate copulatory ducts in ventral view; adjective.
Distribution. China (Sichuan) (Fig. 16). Diagnosis. This new species can be distinguished from other Campanicola species by the following characteristics: epigynum dissymmetric; copulatory pores located on the anterior margin of the atrium; copulatory ducts short, winding simply (Fig. 9D, E).

Campanicola heteroidea
Etymology. The specific name is derived from the Latin adjective heteroideus, meaning asymmetrical, referring in essence to the dissymmetric epigynum structure; adjective.
Distribution. China (Guizhou) (Fig. 16). Diagnosis. This new species is similar to C. volubilis sp. nov. in having the spherical spermathecae, the long and looped copulatory ducts which start from the lateral and anterior part of the atrium, extend anteriorly, then curve several times and enter the spermathecae laterally and ventrally, but can be distinguished from the latter by the following characteristics: 1. The copulatory pores are slightly separated from each other in this new species (Fig. 10D, F), but close to each other in C. volubilis sp. nov. (Fig.  11D, F); 2. The spermathecae are widely separated in this new species (Fig. 10D-G), but slightly separated in C. volubilis sp. nov. (Fig. 11D-G).

Campanicola tauricornis
Etymology. The specific name is derived from the Latin adjective tauricornis, meaning ox horn-shaped, referring to the shape of the copulatory ducts in dorsal view; adjective.
Distribution. China (Hainan) (Fig. 16).    Diagnosis. Males of P. ducta are similar to Parasteatoda cingulata (Zhu, 1998) and Parasteatoda transipora (Zhu & Zhang, 1992) in having a long and looped embolus (Figs 13D-F, 14), but can be distinguished from them by the long and slender conductor with a sharp end (Figs 13D, E, 14). Females of P. ducta differ from all other Parasteatoda species by the relatively smaller spermathecae enclosed laterally by the copulatory ducts (Fig. 12D, E).

Discussion
Eight cobweb spider species building detritus-based, bell-shaped retreats from China are reported in the current paper, including five new Campanicola species, two known Campanicola species and one known Parasteatoda species. However, all new species are reported only based on the female specimens because the male individuals are relatively difficult to collected in the field. According to our experience both in field collection and feeding in the lab, the males after maturity often stop weaving webs and leave their retreats to search for females. We investigated more than 500 retreats of C. campanulata in the field for research focused on its web-weaving behaviour, and only 21 males were collected, often found together with females (manuscript in preparation). Therefore, more thorough collecting or rearing juveniles in the lab may be needed to find further male individuals for these new species in the future. The type of bell-shaped retreat is rare in the family Theridiidae, and found only in four related genera: Achaearanea, Cryptachaea, Parasteatoda and Campanicola (Henschel and Jocqué 1994;Zhu 1998;Yoshida 2009Yoshida , 2015Yoshida , 2016. All of them belong to the subfamily Theridiinae according to both morphological and molecular phylogeny (Agnarsson 2004;Liu et al. 2016). The relationship between these four genera is relatively complicated. And their respective monophyly remains to be verified. Many species in Parasteatoda and Cryptachaea were transferred from Achaearanea, and some species in Parasteatoda were transferred to Campanicola (Yoshida 2008;Backup et al. 2010;Yoshida 2015). Moreover, some Parasteatoda species are quite different from others, for example, the spermathecae of Parasteatoda transipora (Zhu & Zhang, 1992) and Parasteatoda cingulata (Zhu, 1998) is significantly smaller than other Parasteatoda species' (Zhu 1998). In addition, information on web-weaving behaviour (especially focused on the detritus-based, bell-shaped retreat) and ecology (such as the trade-off between the safety and predation) of these spiders is still limited. Therefore, a natural next step upon completing this taxonomic study would be to analyse and understand the evolution of the retreat and related traits.