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1 December 2010 Possible Function of Spatulate Setae Surrounding the Papillae Anales of Sarota Butterflies (Riodinidae: Helicopini)
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Lepidopteran eggs can face high levels of mortality due to a variety of factors including environment, predators, and parasitoids (e.g., Hilker 1994; Obermaier et al. 2006; Sansone & Smith 2001). Ovipositing females are thought to show various traits that may help escape these pressures, including egg placement, shell toxins, and chemical crypsis (e.g., Obermaier et al. 2006; Scoble 1992).

During the course of fieldwork in Central and South America, we observed oviposition by several species of Sarota (Riodinidae) butterflies. As far as is known, larvae of this genus feed on tiny epiphyllic lichens, mosses, and liverworts growing on the surface of tropical leaves (DeVries 1988, 1997). We observed a distinctive behavior associated with egg laying in S. subtessellata (Costa Rica, n = 1), S. gyas (Ecuador, n = 2), and S. chrysus (Ecuador, n = 1). After landing on a leaf, females walked slowly across its surface, dragging the tips of their abdomens, sometimes for up to five minutes before depositing an egg (Fig. 1). They occasionally walked to the lower surface of the leaf, sometimes pausing for several minutes, but always returning to oviposit on the upper surface. Upon close examination of the eggs, we noted that each was entirely covered with scraps of epiphylls glued to the chorion. Subsequently, when observing the external morphology of female genitalia of these and other Sarota spp., we noted the obvious presence of strange, stiff, apieallyrecurved, spatulate setae surrounding the papillae anales. These have been described and illustrated by Hall (1998), though he indicated their function remains a mystery. Although these setae are considered a synapamorphy of the Helicopini, encompassing Helicopis, Sarota, Anteros, and Ourocnemis (Hall 1998), similar structures are present in some moths in the Geometridae and Tortricidae (Pellmyr 1980; Scoble 1992). For Sarota, we also clearly observed the spine-like setae described by Hall (1998), located between the spatulate setae and the ostium bursae.

Fig. 1.

A female Sarota subtessellata drags her abdomen across an epiphyll-covered leaf, presumably using modified setae surrounding the papillae anales to scrape and gather epiphyll scraps for camouflaging her eggs. (Photo P. J. DeVries).

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In at least one tortricid moth these spatulate scales are considered to facilitate covering eggs with debris (Scoble 1992). In concert with these assertions, our observations strongly suggest that spatulate and spine-like scales and setae of Sarota are used to scrape and gather scraps of epiphylls, which are then glued to the egg. This behavior likely provides effective visual and chemical camouflage for eggs deposited on their epiphyll-covered oviposition substrates. Future observations and experiments on the covering of eggs with debris by lepidopterans may yield important clues as to the effectiveness of this behavior in deterring ants and/or egg parasitoids. Similarly, observations on the function of these structures in other genera within the Helicopini may shed light on their evolutionary origin.

Acknowledgements

We thank J. O. Stireman III for help with literary sources and J. P. W. Hall for confirmation of species identifications. We are grateful to the owners and staff of La Selva Lodge and Hakuna Matata Lodge for their hospitality in Ecuador, and the Smithsonian Tropical Research Institute for support in Panama. HFG acknowledges the support of Matt Kaplan & John V. Moore. This study was funded in part by NSF grants DEB-0346729 and DEB-0527441. This is publication no. 193 of the Yanayacu Natural Histoty Research Group.

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Harold F. Greeney, Carla M. Penz, Phillip J. DeVries, and Thomas R. Walla "Possible Function of Spatulate Setae Surrounding the Papillae Anales of Sarota Butterflies (Riodinidae: Helicopini)," The Journal of the Lepidopterists' Society 64(4), 216-217, (1 December 2010). https://doi.org/10.18473/lepi.v64i4.a7
Received: 5 March 2009; Accepted: 23 January 2010; Published: 1 December 2010
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