Pacarina, Distant, 1905

Aiello, Annette & Stucky, Brian J., 2020, First host plant record for Pacarina (Hemiptera, Cicadidae), Neotropical Biology and Conservation 15 (1), pp. 77-88 : 77

Ecology and life history of Pacarina in Panama

Our results provide the first definitive host plant record for any species of Pacarina . Although we did not directly observe any female Pacarina ovipositing in the potted Dracaena trifasciata , there is no other convincing explanation for the presence of so many nymphal Pacarina on the plant. It is conceivable that oviposition occurred elsewhere and the hatchling cicadas were carried to the D. trifasciata by the wind, but given the pot’s relative isolation from any nearby vegetation and the large number of cicadas that emerged from it, this is highly unlikely. In any case, there can be no doubt that the D. trifasciata was the food source for the developing nymphs.

Dracaena Vand. ex L. ( Asparagaceae , but formerly of the Ruscaceae ) is a genus of about 60 species of both terrestrial and epiphytic plants, mostly from Africa and south Asia, with two species endemic to the Neotropics and only one, D. americana Donn. Sm., a tree, found in Central America, including Panama ( Zona et al. 2014). In Panama, D. americana appears to be limited to the extreme western part of the country ( Zona et al. 2014). If we assume that D. trifasciata is at least distantly related to the natural host plants of the reared Pacarina species, the most likely candidates in Panama include three Agave species (angustifolia, hurteri, seemanniana) and Furcraea cabuya , all belonging to the Asparagaceae (s.l.). D. trifasciata is terrestrial and is native to South Africa. It is among the most popular pot plants worldwide.

Though no information is available about native hosts in Panama, Young (1974) studied the possible host relationships of Pacarina in grasslands in western Costa Rica. He observed that nymphal exuviae were found among patches of Rhynchospora (= Dichromena ) ciliata (Vahl) ( Cyperaceae ) and inferred that this sedge was the probable food plant. The only similarity between Dracaena and Rhynchospora is that both are monocots, which could be a significant relationship in this case. Young did not identify the species of Pacarina he studied and suspected that it was undescribed.

The Pacarina in our study eclosed over a 53-day period from December 16, 2006 to February 6, 2007, but 21 of the 29 total individuals (≈ 72%) eclosed during the 14 days from December 22 to January 4. This timing matches well with the emergence phenology of P. puella in Las Cumbres ( Wolda and Ramos 1992), a lowland residential area in south central Panama that is only ~20 km away from our study location and expected to have qualitatively similar habitat.

The total life cycle length of the reared Pacarina is unknown. However, the D. trifasciata on which the cicadas were reared was divided from a parent plant and re-potted on 5 August 2005. No cicada nymphs were observed in the soil at that time, although it is possible that early instars were present and overlooked due to their small size. We think that is unlikely, though, for two reasons. First, early stage cicada nymphs are extremely fragile and vulnerable to desiccation ( Beamer 1928) and could have easily been killed while dividing and re-potting the parent plant. Second, no cicadas are known to have emerged from any of the other plants derived from the original parent, which strongly suggests that no cicada nymphs were present on the roots of the parent plant. If the nymphs entered the soil after the parent plant was divided, this places an upper bound of 498 days on the nymphal development time of the earliest-emerging cicadas. Assuming that all of the reared Pacarina derived from the same oviposition event, the 53 days between the first and last adult cicada eclosions indicates considerable variability in egg and/or nymphal development times for this species of Pacarina .

Taxonomy and biogeography of Pacarina

The genus Pacarina is distributed from the southwestern United States (US) southward through Central America, including Panama, and presently comprises three described species: puella Davis, schumanni Distant, and shoemakeri Sanborn & Heath ( Sanborn et al. 2012; Sanborn 2018). All three species are small cicadas that resemble each other in general appearance. Two species, P. puella and P. schumanni , have previously been recorded from Panama ( Sanborn 2018). Pacarina puella is reported as the most widespread species in the genus, having been collected as far north as the state of Oklahoma in the US, in Mexico, and in Central America as far south as Panama ( Drew et al. 1974; Wolda and Ramos 1992; Sanborn et al. 2012).

Although the recent key to Pacarina published by Sanborn et al. (2012) would identify our specimens as P. schumanni , the wing morphology does not match Distant’s description (1905a) and the general habitus and genitalia are markedly different from that of the P. schumanni holotype. Similarly, the terminalia of the holotype of P. puella differ from those of the reared specimens, especially in the form of the pygofer and uncus. The northern geographic range and restricted habitat requirements of P. shoemakeri ( Sanborn et al. 2012) exclude it as a possibility.

Until more complete data are available for Pacarina in Panama and elsewhere in Central and North America, we prefer not to describe our specimens as a new species and risk further confusion. More complete morphological, ecological, and bioacoustic data for P. puella and P. schumanni from at or near their type localities would be especially useful, as would a reexamination of existing specimens in various collections. The labels from the holotype of P. schumanni give the collecting locality as "Atoyac, Vera Cruz" but the labels from the holotype of P. puella only state that the collecting locality was “Mex.” However, Walker, in his original description of Cicada signifera (= P. puella ), reported "Orizaba, Mexico" as the holotype locality ( Walker 1858). These two type localities are both near the western border of the modern Mexican state of Veracruz, separated by only about 35 km. We were unable to examine any other specimens of P. puella or P. schumanni from these locations, and no ecological or bioacoustic data is available for either species from their type localities. Sueur (2002) studied P. schumanni in eastern Veracruz, but virtually all published natural history information for P. puella comes either from the northern limit of its range in the United States or the southern limit of its range in Panama. Bioacoustic data would be particularly valuable, because cicada species’ unique calls provide the single most important mechanism for pre-zygotic reproductive isolation ( Alexander and Moore 1958; Boulard 2006) and there are numerous examples of morphologically cryptic cicada species that are most easily distinguished by their calling songs (e.g., Davis 1922; Alexander and Moore 1962; Popov 1989; Marshall and Cooley 2000; Quartau and Simões 2005; Sueur and Puissant 2007; Cole 2008; Gogala et al. 2008; Popple 2013; Stucky 2013; Ewart 2018).

We also note that the striking ecological divergence between northern and southern populations of P. puella suggests that P. puella , as currently recognized, might not even be a single species. In North America, P. puella is typically found in relatively dry habitats on or near mesquite ( Fabaceae : Prosopis spp.) ( Davis 1917, Sanborn et al. 2012, Sanborn and Phillips 2013), which led Sanborn et al. (2012) to conclude that mesquite was its host plant. In fact, this ecological association is one of the diagnostic features that separate P. puella from the recently-described P. shoemakeri , which instead is found primarily on junipers ( Sanborn et al. 2012). Although at least one species of Prosopis does occur in Panama ( Condit et al. 2011), Prosopis evidently is not found on Barro Colorado Island ( Croat 1978), where cicadas that have been identified as P. puella are nevertheless relatively common ( Wolda 1989). Either Prosopis is not an obligate host for P. puella or the northern and southern populations represent different species, either of which might be true P. puella . Again, a critical re-examination of previous literature records for Pacarina , combined with more thorough ecological and bioacoustic data, are needed to properly resolve the taxonomy of this genus.