Pheidole sicaria, Wilson, 2003

Longino, John T., 2019, Pheidole (Hymenoptera, Formicidae) of Middle American Wet Forest, Zootaxa 4599 (1), pp. 1-126 : 58-59

Pheidole sicaria

Pheidole sicaria Wilson, 2003: 232 . Holotype major worker: Costa Rica, Puntarenas, Llorona, Corcovado National Park (P. S. Ward) [MCZC, not examined].

I use a broad definition of Pheidole sicaria , almost certainly comprising a set of somewhat separate genetic clusters distributed across Costa Rica and Panama. In addition to sharing a general morphometric profile, the minor workers have the face smooth and shiny, the head weakly tapered posteriorly in full face view, the promesonotal groove impressed, and the propodeal spines at least as long as the posterior face of the propodeum. The major workers have the inner hypostomal teeth widely spaced and acicular, and the face almost entirely smooth and shiny. They occur in lowland to mid-elevation mature wet forest, where they live exclusively in the low arboreal zone. Nests are found under epiphytes in old treefalls and in loose, irregular masses of debris lodged in low vegetation. Workers are collected in beating samples and Malaise traps, but rarely at ground baits or in Winkler samples of forest floor litter and rotten wood. One major worker was collected as prey in a Simopelta column.

However, there is inter-populational variation in details of propodeal spine shape and overall pilosity, and these separate forms can be in close proximity, suggesting a mosaic of genetically differentiated groups.

Type form: The type specimens of P. sicaria were collected by Phil Ward at Llorona in Corcovado National Park , on the Osa Peninsula of Costa Rica. This is a lowland rainforest site, at 100 m elevation. The minor workers have relatively thin, somewhat upturned propodeal spines. The first gastral tergite has sparse appressed pubescence and scattered long erect setae (judging from the images provided in Wilson 2003). The major worker has the first gastral tergite densely pilose, scruffy, with suberect setae of variable lengths. The head is red brown.

Form 1: Small cloud forest patches occur in the center of the Osa Peninsula, around 700 m elevation. A collection by myself from this cloud forest area is similar in most respects, but the first gastral tergite of the major worker has pilosity like the minor worker: fully appressed sparse pubescence, and scattered long erect setae. Collections similar to this form are also known from around 500 m elevation on the Barva transect above La Selva Biological Station, and from 900-1000 m elevation on the eastern slopes of the Cordillera de Tilarán and Cordillera de Guanacaste.

Form 2: A distinct form, and almost certainly a separate species, occurs around 1100 m on the Barva transect and at similar elevation near Fila de Matama, on the Atlantic slope of the Talamanca range. The minor worker has longer, more robust, and less upturned propodeal spines. The pilosity on the gaster is a mix of suberect short setae and erect very long setae. The major worker has a yellow head, constrasting with the red brown body. The pilosity on the gaster is scruffy, like the type specimens.

Form 3: A series of minor workers were collected from low vegetation at a 400 m elevation site in Braulio Carrillo National Park, at the old Carillo station close to where the Guapiles highway is now. These workers have the robust spines of form 2, but the gastral pilosity is all of relatively short, erect setae. Also, the sculpture on the katepisternum is stronger, with the foveolation overlain with weak rugulae.

Form 4: This form is known from multiple collections from the Rio Savegre drainage on the Pacific slope of the Talamanca range, at a wet forest site around 800 m elevation (Ranchos Tinamu). The propodeal spines are thin and relatively upturned, like the types. The minor workers have the first gastral tergite with a relatively dense layer of fully appressed pubescence, and no or very few longer erect setae. The major worker has the head color somewhat mottled, intermediate between the types and form 2. The face is more strongly sculptured, with relatively more developed arcing carinulae on the anterior half of the face, and widely spaced, shallow puncta (not foveolation) on the vertex. The gastral pilosity is like the minor worker, with a dense layer of appressed pubescence, and sparse longer erect setae.

Form 5: Two collections from cloud forest sites in Panama are very similar to Form 1, differing only in somewhat longer, less upturned propodeal spines (but still thin, not enlarged at the base like forms 2 and 3).