Simopelta andersoni Mackay and Mackay 2008

Ponerinae, Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia


worker face view

worker lateral view

Additional images:
Worker, clypeus and mandibles (small, large); sem of face (large, small); mandible (large, small); lateral view (small, large); mesosoma, lateral view (large, small; line drawing of face (large, small).
Queen, face view (small, large); lateral view (small, large); dorsal view (small, large); line drawing of dorsal view (small, large); face view (small, large); lateral view of mesosoma (small, large); petiole, posterior view (small).

Range

Costa Rica: mountainous regions from 200-1200m elevation.

Identification

Mandible with one or more teeth or denticles between the basal and two apical teeth; anteromedian clypeal border triangular, strongly projecting, without spine; sculpture on face and mesosoma composed of sublinear striae, transversely arcuate on face; head relatively narrow, head width/head length less than 0.8.

A collection from Rancho Quemado on the Osa Peninsula has clypeus shape more like paeminosa and sculpture a bit more vermiculate than other material.

Similar species: JTL-004.

Natural History

All Simopelta species are nomadic group raiders, convergent with Ecitoninae. See additional information under genus account.

This species occurs in mature montane forest habitats, with highest density around 1000m elevation. This is the most common species I have encountered in Costa Rica; I know of 25 separate collections. I have seen collections from Estacion Pitilla (700m), Monteverde (1150m on Pacific side), Penas Blancas (8-900m), Braulio Carrillo National Park (various elevations above 500m), San Vito (Wilson Botanical Gardens, 1200m), and Rancho Quemado (Osa, 200m). The Rancho Quemado collection is morphologically distinct and may represent another species.

Selected Records

JTL12Sep82/1030: (Carrillo) A column was moving brood from one cache to another. The column's endpoints seemed to be the two caches, 5-10m apart. The caches were large piles of brood of uniform age. One cache was on the ground beneath dead leaves. These larvae were being carried to the second cache inside a dead Heliconia petiole, 20cm above the ground. (Larvae from this collection described in Wheeler & Wheeler 1986.)

JTL1384: (Zona Protectora, 880m) 14 Jul: Wet forest. A column of workers led to a hole at the base of a treefern stump. Excavating yielded a cache of brood of uniform size, a few cm's in from the stump base at ground level. Many workers were escaping down a hole into the soil. I excavated about 10cm further in that direction, and unearthed a queen. She was attended by a single worker when I found her, the worker riding with head and forelegs on the queen's abdomen. There was just the single brood pile. I collected the queen, about 25 workers, and about 15 larvae alive, and took them back to La Selva for observation. They were collected into a whirlpac bag. 15 Jul: Today at 1100hrs I transferred them to a 9cm dia plastic petri dish. This involved chilling for about 10 minutes in a refrigerator. Within a few minutes the larvae had been moved to one place and the queen was standing on top of the pile. 24 Jul: Over the past several days I have twice fed ant brood to Simopelta. Workers pick up the brood and carry it to their brood. I presume they are eating it. A week ago I fed them some Pheidole fiorii brood. Yesterday I fed them brood from Pheidole dossena (collection #1428). I returned to Santa Barbara, California with the live colony. Although out of food, they ignored larvae of Camponotus dumetorum and Crematogaster ashmeadi which I had in cultivation. The workers and the queen died one by one.

JTL1488: (Penas Blancas) Forested ridge just before reaching Eladio's house. I first saw a column crossing the trail. I followed them back to where they were emerging from under a stone. The other end of the column was the leading edge, and they were slowly moving away from the rock. I turned the rock, and the entire colony was clustered tightly on the underside of the stone. There were hundreds of workers (probably less than 1000), one queen, and tiny brood. There was very little brood, and what there was was in the form of small white packets that workers carried away in their mandibles. When I turned the stone the queen was one of the first individuals to disassociate herself from the cluster. She moved about on the stone unattended for a while (10-20 seconds) and then joined the column of retreating workers that were leaving the stone. As she joined the column she acquired an attendant worker that placed its head and forelegs over her abdomen and they ran off together. The cluster at first was about 4cm wide and 1cm high. After exposure it slowly melted, as workers gradually left the outer surface of the cluster. It took over a minute for the cluster to completely dissipate. The rock surface was clean and I could closely watch the exodus. Two myrmecophiles appeared as the cluster dissolved. Early-on, a phorid fly was observed running with the workers. At the very end, as the last worker left, a small parasitic wasp remained that had been deep in the center of the cluster. The fly and the wasp were collected into a vial with the ant sample. Lubomir Masner identified the wasp as a member of the genus Doliopria in the Diapriidae. The vial also contains the remains of a dead worker of Pheidole rogeri. The dead ant was on a stick near the nest entrance, and many workers stopped and antennated it as their column passed over it.

JTL2038: (Penas Blancas) wet forest, colony migration column on trail. I collected the queen as she traveled with the column. The queen was attended by only one worker. I saw no noticeable knot of workers nor thickening of column near queen. Pheidole soldier head capsule in collection.

JTL4Jul84/1438: (Penas Blancas) wet forest, around Guindon cabin. A colony was in underground chambers on the bank of a stream in the forest. The chambers were in loose, clay soil. The colony seemed to be diffusely spread in the clay bank, extending back in about 20cm and ca.10cm below the surface. There was a single main entrance in the vertical clay bank. A raiding column was returning with booty from a Pheidole fiorii nest greater than 5m away. The raided nest was a pendant agglomeration of chambered humus-like material on two strap-shaped fern leaves. The nest hung about 1.5m above the stream. When I broke into chambers of the Simopelta nest, it appeared that dismembered booty (larvae and pupae) were scattered over the floor with feeding Simopelta larvae. An outer chamber contained a few pupae, which were in cocoons.

I collected the entire raided Pheidole nest in a plastic bag. The nest was completely abandoned. All that remained were various brood, 1 callow worker, a male, and an alate queen that was cloistered in an inner chamber, probably as yet unnoticed by the Simopelta. There was abundant queen brood in the nest, and many of the queen pupae were neatly cut up into head, trunk, and gaster, I presume in preparation for transport back to the Simopelta nest.

On examination of the collection in the lab, there seemed to be two kinds of Simopelta larvae: short pea-shaped larvae and larger, longer, curved larvae. Booty included larvae and pupae, I think of the Pheidole fiorii nest being raided. There were also two cocoons with ponerines(?) inside. They seemed too small to be Simopelta. [I do not have these cocoons; I must have sent them to the Wheelers with the Simopelta larvae.]

Larvae from this collection were sent to Wheelers and described in Wheeler and Wheeler (1986).

Comments

I now have three queens of Simopelta, two of this species and one of oculata. The two queens of andersoni look nearly identical, even though they come from two different cordilleras (Tilarán and Volcanica Central). The general habitus is very similar between the two species, but there are some consistent differences. The eyes of the andersoni queens have a very curious appearance. The eye is a completely flat, smooth, shiny surface, oblong, rimmed, and slightly sunk into the surface of the head. They look like oblong coins pressed onto the surface. In contrast, the eyes of the oculata queen are more typical, with a convex cornea. In both cases the eyes are possibly composed of multiple, fused facets. The ventral margin of the swollen queen petiole is more or less flat in andersoni, leading to a small anteroventral tooth. In contrast, the oculata queen has a prominent triangular projection at midlength. The triangular projection is also evident in the figure of the oculata queen in Gotwald and Brown (1967). This difference in the shape of the ventral margin does not seem to show similar differences in workers.

Mackay and Mackay (2008) described this species and two other similar species: quadridentata and pentadentata. All three were from sites in Costa Rica. Simopelta andersoni and quadridentata differed from pentadentata in having four mandibular teeth instead of five. However, amongst the 30 different collections of andersoni I have examined, I find continuous variation in the presence of the fifth tooth. It varies among colonies and sometimes between mandibles of the same individual. Simopelta andersoni and quadridentata differed in eye size, with EL of quadridentata being about 0.07mm and andersoni being 0.10-0.14mm. I have workers from the type series of quadridentata, and I measured EL as 0.10. At this point I consider quadridentata and pentadentata to be intraspecific variants of S. andersoni.


Page author:

John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu

Last modified: 5 April 2009.


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