Formicidae, Hymenoptera, Insecta, Arthropoda, Animalia
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Identification
Mandibles with 5 distinct teeth, apical tooth largest, proximal tooth considerably smaller, remaining three teeth the smallest and subequal in size; mandibles striate; occipital carina not visible in face view; propodeal suture not deeply impressed; ventral margin of postpetiole produced as a rounded lobe; color orange; HW 0.81-0.93; HL 1.00-1.12, SL 1.02-1.12; WL 1.29-1.45 (n=13, from Brandao 1990).
Range
Colombia, Costa Rica, Panama, Venezuela. Costa Rica: Atlantic slope wet forest.
Natural History
Forel (1899) reported that the type specimens were collected by A. Alfaro from a rotten log. Kugler collected specimens in Colombia, from a "large nest in rotten log, soil - rocks, under forest" (reported in Brandao 1990).
I have observed modestus numerous times in Costa Rica. It prefers mature wet forest. It appears to be rare at La Selva, but becomes increasingly abundant at higher elevations. At La Selva, I have seen the occasional worker from a sifted litter sample or at a bait on the forest floor, and once I found an isolated worker in the live hollow stem of a live Solanaceous scandent shrub (Witheringia?). At higher elevations above La Selva and in Penas Blancas, I frequently find modestus building soil shelters up trees and under liana stems, where they tend Coccoidea. Colonies are subterranean, can be very large, and may be polygynous.
Selected Records:
Sifted litter samples from the forest floor; samples from Hitoy Cerere Biol. Reserve, La Selva, Rara Avis, 17km N Vol. Barba, Penas Blancas.
Longino #0154: 22km N Volcan Barba. Primary wet forest, 2000-2100hrs (dark). A long vertical length of carton over aroid stems (ground level to over 2m) covered many of these ants, and the ants were tending homoptera.
Longino #2019: Casa Eladio, Rio Penas Blancas. Wet forest. A nest several meters across was on the bank of a small stream. A large area of excavated soil covered the ground. There were hundreds of small entrances, and my excavations in the surface soil turned up only scattered workers, and no brood. As I dug deeper into the center of the nest (more than 20cm deep) workers became more dense and I began finding adult males and some brood. At the depth of my machete workers were very dense, brood more abundant, and two dealate queens were turned up. The soil was very friable, and I could not discern any gallery or chamber structure. Given that I was digging in only a small part of the colony, and turned up two queens, the colony must have had many queens. At the periphery of the colony I turned up mealy bug-like Coccoidea in the soil.
Longino #2697-s: Casa Eladio, Rio Penas Blancas. Wet forest clearing. Recently felled Licaria tree. Under moss and epiphyte mats.
Longino #2279: Casa Plastico, 17km S Pto. Viejo. Wet forest; three colonies observed under moss mats and accreted soil on trunk bases of Hedyosma trees (Chloranthac.). All three had pentatomids, adults and nymphs, with the ants under the moss mats.
Literature Cited
Brandao, C. R. F. 1990. Systematic revision of the Neotropical ant genus Megalomyrmex Forel (Hymenoptera: Formicidae: Myrmicinae), with the description of thirteen new species. Arquivos de Zoologia (Sao Paulo) 31:411-481.
Forel, A. 1899. Formicidae. Biol. Cent.-Am. Hym. 3:1-160.
Page author:
John T. Longino, The Evergreen State College, Olympia WA 98505 USA. longinoj@evergreen.edu
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