Forelius pruinosus

Guerrero, R. J. & Fernández, F., 2008, A new species of the ant genus Forelius (Formicidae: Dolichoderinae) from the dry forest of Colombia., Zootaxa 1958, pp. 51-60: 57-59

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Forelius pruinosus


Forelius pruinosus  HNS  (Roger 1863)

(Fig. 6)

Material examined: Colombia. (3w), Magdalena; Santa Marta; Vda. Mosquito. 11°10'23.6"N 74°10'45"W 96 m; Manual collection; 03.Jan.2008; D. Olivero & M. Escarraga, coll. Deposited in Insect Collection of University of Magdalena (CEUM), Santa Marta, Colombia.

Geographic distribution: Bahamas, Colombia (Magdalena), Costa Rica (Guanacaste), Cuba, Guatemala, Mexico, Panama, The West Indies, USA [Arizona, California, Florida, Georgia, Missouri, North Dakota (Wheeler & Wheeler 1963), Texas].

Cuezzo (2000) provided a taxonomic key for all species of Forelius  HNS  known. Due to the new synonymy between F. analis  HNS  and F. pruinosus  HNS  (Ward 2005) and the description of F. damiani  HNS  , we provide a new key for the species with circular propodeal spiracle, with the exception of F. keiferi  HNS  . The descriptions of F. keiferi  HNS  and F. pruinosus  HNS  given in Cuezzo (2000) overlap in many characters and the status of F. keiferi  HNS  as a species distinct from F. pruinosus  HNS  is not certain.

Key to species of Forelius  HNS  Emery with spiracles rounded [based on workers; modified from Cuezzo (2000)]

1. Small workers (TL 1.6 - 1.7 mm). Scapes barely reaching vertex margin (SI <90). Mesosomal outline always continuous in lateral view. (Argentina, Brazil, Paraguay)..................... pusillus (Santschi)  HNS  (Fig. 4)

- Worker size variable (TL 1.4 - 2.5 mm). Scapes reaching or surpassing vertex margin by at least 1/6 of their length (SI> 90). Mesosomal outline variable.....................................................................................2

2. Pronotum bearing only two erect setae. Dorsal face of propodeum lacking erect setae. (Colombia, Costa Rica, USA)...................................................................................................... damiani  HNS  sp. nov. (Fig. 1 & 2)

- Pronotum bearing more than two erect setae. Dorsal face of propodeum bearing erect setae. Note: Some evidence of intergradation between F. pruinosus  HNS  and F. mccooki  HNS  (Ward 2005) suggests that F. pruinosus  HNS  may contain a number of cryptic species, and may also hybridize with the very similar F. mccooki  HNS  ........3

3. Mandibles with four teeth and three to four denticles. Pronotum usually with six erect setae. Dorsal face of mesosoma bearing more than 10 erect setae. (Jamaica, Mexico, USA) ...... mccooki (McCook)  HNS  (Fig. 5)

- Mandibles with five teeth and one or two denticles. Pronotum usually with four erect setae. Dorsal face of mesosoma bearing 2 to 6 erect setae. (Bahamas, Colombia, Costa Rica, Cuba, Guatemala, Jamaica, Mexico, Nicaragua, Panama, USA)........................................................................... pruinosus (Roger)  HNS  (Fig. 6)


Forelius damiani  HNS  and F. pruinosus  HNS  are the first species of the genus Forelius  HNS  known from Colombia. Both species have been collected in the lowland dry forest of the Sierra Nevada de Santa Marta while F. damiani  HNS  has also been collected in Zambrano (Bolivar), northern Colombia. The Zambrano specimens do not differ from those of the type locality. The workers of F. damiani  HNS  from Costa Rica differ somewhat in size (TL 1.50 - 1.68 mm in Costa Rica vs. TL 1.40 - 1.58 mm in Colombia) and the length of the scapes (exceeding the vertexal margin by 0.04 mm in Costa Rica, not exceeding the vertexal margin in Colombia). While the TL of the workers showed differences between the populations of Costa Rica and Colombia, the length of mesosoma is less variable and the measurements for the two countries broadly overlap (MsL 0.46 - 0.56 mm in Costa Rica vs. MsL 0.44 - 0.58 mm in Colombia). Specimens from Costa Rica are darker brown than those from Colombia.

Forelius damiani  HNS  is relatively similar to F. pruinosus (Roger)  HNS  , but F. damiani  HNS  has only two erect pronotal hairs while F. pruinosus  HNS  can have two to four erect pronotal hairs; the promesonotum of F. damiani  HNS  is lower compared with F. pruinosus  HNS  ; the dorsal face of the propodeum is longer than the declivitous face in F. damiani  HNS  , moreover it lacks propodeal hairs; and F. damiani  HNS  is smaller than F. pruinosus  HNS  in some measurements such as TL, HL, HW and SL (see measurements above and Cuezzo (2000) for comparison). Forelius damiani  HNS  is similar to F. pusillus  HNS  , however several characters show differences: the mandibles of F. damiani  HNS  have four teeth while those of F. pusillus  HNS  have five; the propodeum of F. pusillus  HNS  has four conspicuous setae but F. damiani  HNS  has none; the workers in F. pusillus  HNS  are a little larger (TL 1.6 - 1.8 mm in F. pusillus  HNS  vs. 1.40 - 1.68 mm in F. damiani  HNS  ). Characters that distinguish Forelius damiani  HNS  from most other Forelius  HNS  species are the circular propodeal spiracle and the absence of erect hairs on the dorsal face of the propodeum.

The occurrence of round spiracles on the new species F. damiani  HNS  reinforces a pattern in which the few species found north of the Amazon basin all have round spiracles, while south of the Amazon many species have elongate, slit-like spiracles and only one species has round spiracles. Several hypotheses can explain this pattern, based on whether round spiracles are plesiomorphic, apomorphic, or homoplasious in the genus. If round spiracles are plesiomorphic, the genus could have originated north or south of the Amazon basin and then dispersed across the Amazon (perhaps during a period of drier climate). Subsequently, elongate spiracles evolved in the south (as one adaptation to arid conditions, reducing water loss through the spiracle) and perhaps allowed a greater diversification there. In the south, forms with elongate spiracles may have displaced previously more abundant and diverse forms with round spiracles. Alternatively, round spiracles could be apomorphic. An initial radiation of forms with elongate spiracles may have occurred in southern South America. Subsequently, a form with round spiracles evolved which was better suited to humid conditions and better able to cross the Amazon Basin. Once on the other side it diversified into the present species found north of the Amazon. Finally, round spiracles could be homoplasious, evolving independently north and south of the Amazon. Further phylogenetic work on the genus is needed to differentiate among these hypotheses.