Short Communication

The Thailand Natural History Museum Journal 12(2): 83-89, December 2018 ©2018 by National Science Museum, Thailand Short Communication Egg Sacs of the Orb-weaving Genus Cyclosa (Araneae: Araneidae) Targeted by Ovipositing Lacewings (Neuroptera: Chrysopidae) Timothy C. Hawes* Akarn Teeranee, Soi 35, Pahonyothin Road, Khet Jatujak, Bangkok, Thailand ABSTRACT: The first evidence of non-mantispid Neuroptera (Chrysopidae) specializ- ing on spider egg sacs for oviposition is reported from Thailand. Prior to this observation, specialization on spiders by neuropterans was believed to be confined exclusively to the Mantispidae, larvae of which are currently only known to locate their prey by active searching and/or phoresy on adult spiders. Observations of the targeting of Cyclosa egg sacs by ovipositing Chrysopidae are described. KEY WORDS: Cyclosa, Mantispinae, Neuroptera, orb-weaver, oviposition INTRODUCTION have been used to test and examine hypotheses that explore the functional Spiders of the genus Cyclosa are relatively significance of these web decorations (e.g. small-sized orb-weavers with a widespread Tseng and Tso, 2009; Tan and Li, 2009; Tan distribution that spans both New and Old et al. 2010). Species records from Thailand Worlds and encompasses both temperate and are still sparse and will no doubt be added tropical biomes (WSC, 2018). They are a well- to in future years - but see Chotwong and studied genus both because of their relative Tanikawa (2013) and Petcharad et al. (2014) abundance and because they are a model for recent additions. Overall, the potential group for the study of the construction and species list for Thailand can be expected to use of stabilimenta (web decorations). Web share many commonalities with the genus decorations assume a variety of morphologies lists provided by Song et al. (1999) and that vary between species and across Tanikawa (2007). ontogenetic stages; typically, silk decorations are only utilized by juveniles, while adults Interspecific interactions of Cyclosa spiders construct their decorations out of detritus, have until now been looked at almost prey remains and molt exuviae. Probably exclusively in terms of predator-prey all species lay their eggs in a silk sac. Most interactions – in particular, how they capture species place this egg sac outside the orb web, insect prey and how they use their stabilimenta but C. mulmeinensis is a notable exception, to hide themselves from predators. The incorporating it into its stabilimentum. interactions reported here are of a slightly different type and with a group of insects In Southeast Asia a number of Cyclosa species whose relations with spiders are much more *Corresponding author. E-mail: [email protected] 84 The Thailand Natural History Museum Journal 12(2), December 2018 poorly known. and unambiguous evidence of ovipositional behavior by Neuroptera as a means of The insect order Neuroptera Linnaeus targeting spiders. Although there have 1758 are ‘net-winged’ insects known for previously been reports of insects laying eggs the predatory lifestyles of their larvae. on spider webs in order to protect them from While adults may or may not be predatory, predators (Nafus and Schreiner, 2008), this almost all larvae are predacious and are is probably the first report of insects using equipped with specialization mandibles of oviposition on and next to webs as a means different types for piercing and sucking. to facilitate predation. Previous studies of Such lifestyles are often facilitated by the mantispids have either emphasized the role oviposition sites chosen by females to lay played by larvae in locating spiders or have their stalked egg rows. Most larval predation only been able to note an association between is targeted at other insects, and lacewings oviposition sites and spider occurrence (La – in particular, the Chrysopidae - are often Salle, 1986; Redborg, 1998). researched and reared in the context of pest management, particularly with regard to MATERIALS AND METHODS aphids (Aphididae) (Tauber et al., 2009). Observations were made in the vicinity However, one group has evolved to specialize of Huay Yai, Banglamung, in the central- exclusively on spiders. Larvae of the eastern province of Chonburi, Thailand. subfamily Mantispinae (Mantispoidea: Whilst carrying out natural history surveys Mantispidae) locate the webs of spiders and observations (e.g. Hawes, 2015, 2016, either by wandering or by phoresy on 2018) the occurrence of neuropteran egg female spiders (Redborg, 1998). As a stalks was noted in direct association with mode of predation - or ‘semi’-parasitism the webs of Cyclosa spiders. The habitat (Killbrew, 1981) – it is probably one of the consisted primarily of mixed secondary most curiously specialized associations in woodland, scrub, and grassy clearings the Arthropoda. It was first discovered by interspersed between small fruit orchards ‘serendipitous’ (Redborg, 1981) discoveries and agricultural fields (mostly growing of larvae in spider egg sacs hatchings made pineapple). Webs examined and noted here by a number of investigators in the 19th and were all made within an area of c. 1km2. early 20th century. Brauer (1869) is generally Observations 1 and 3 were made at the verge considered to have demonstrated that spider of a rural road with a cleared and managed eggs are the obligate food of larvae of the perimeter of short grass and trees with family. Subsequent biologists have expanded secondary woodland behind it. Observation the list of associates and explored some of the 2 was made in the same area described by intricacies of the relationship – Redborg and Hawes (2018), just above ground-level in the Macleod (1984) demonstrated, for example, low canopy of a coconut tree at the edge of an that phoretic larvae feed on the hemolymph orchard and about 500 m from the rural road. of their spider transporters. An overview of Photographs and notes were made of the the known biology of the Mantispidae was associations, and egg stalks were taken home provided by Redborg (1998). to hatch (further details below). Independent observations of Cyclosa egg sac targeting This paper reports the first observations of and of larvae predating (one in situ, one ex non-mantispid Neuroptera targeting spiders situ) spiderlings were made. Three sets of for larval prey. It also provides the first direct observations are described; all observations Timothy, Title: Egg sacs of the orb-weaving genus... 85 were made between February and March RESULTS 2013. A fourth observation of a batch of egg stalks found laid on the tip of a grass stem Observation 1. 27 February 2014. Neuropteran about 15 cm from the bridge line of a Cyclosa egg stalks were found laid on the bridge line ‘insulana-type’ web is not included, as the of a C. mulmeinensis web with egg sacs inlaid proximity, while probably spider-associated, as ‘balls’ into the central stabilimentum (Fig. was not considered specific enough. An 1). Egg stalks were collected and hatched (Fig. additional set of three further associations of 2) on 1 March 2014. Larvae were identified to stalks with empty (non-Cyclosa) spider webs be of the Family Chrysopidae. Larvae were were made, but these are not described here predaceous and trash-carrying, after a few days on the basis of their ambiguity (it was not only one was left, with a trash ‘backpack’ of the possible to exclude the possibility that the skins of the siblings it had cannibalized. An egg egg stalks were laid after web abandonment). sac from another Cyclosa sp. had been collected and hatched on 3 March 2014. The remaining Although it is likely that many species – probably chrysopid larva readily attacked and ate the including the one noted here – in Thailand, have spiderlings that emerged from this egg sac yet to be described, the larvae of Neuroptera when offered them singly (Fig. 2c). However, have distinctive morphologies at the Family spiderlings were capable of silk-deployment so level (Tauber et al., 2009). Thus, it was possible the larva was not always successful. Due to an to definitively rule out a mantispid association insufficient familiarity with mantispid biology by general morphology of the mandibles at the time of the observations, the larvae were (Redborg, personal communication). Further not tested with an unhatched spider egg sac (but taxonomic specification of the chrysopid was see observation 3 below). not possible on the basis of available material but the functional significance of even this Observation 2. 11 March 2014. Neuropteran basic level of differentiation is that it effectively egg stalks were found laid directly next to the rewrites our previous understanding of the egg sac of a Cyclosa sp. (Fig. 3). This species exclusivity of Mantispidae-spider relations. of Cyclosa lays its eggs outside the web. The Cyclosa mulmeinensis was identified with web was hung in the shelter of a coconut palm reference to Roberts (1983) and Koh (1991). frond and the egg fixed onto the ‘finger’ of one The latter paper provides prior record of the of these fronds. The proximity of the egg stalks occurrence of C. mulmeinensis in Thailand. The and the Cyclosa egg sac was unambiguous. two other webs of Cyclosa are noted to be of the ‘insulana’ type (elongate abdomens; patchwork Observation 3. 20 March 2014. Another opisthosomal colouration; vertical, relatively un- Cyclosa sp. web was found strung across compacted trash-lines) – but noting Tanikawa’s the lower branches of a tree with its egg sac (1992) remarks on what is probably an overly fixed to one of the branches. A relatively misidentified species, the spiders are given large trash-‘backpack’ carrying neuropteran only generic designation here (‘Cyclosa sp.’). larva – later determined to be a sub-adult – The samples were not collected but subsequent was observed attacking the egg sac. The egg collections (Hawes, unpublished data) have sac and larva were collected. The larva was examined the genitalia of a number of Cyclosa left with the egg sac and subsequently molted from Thailand, confirming the C.

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