Ants of Africa and Madagascar: A Guide to the Genera

by Brian L. Fisher, Barry Bolton

Overview

Across the Afrotropical and Malagasy regions, ants are one of the most conspicuous and ecologically dominant animal groups. From driver ants to weaver ants, there are over 2,000 species in Africa alone and over 600 in Madagascar.
 
Ants of Africa and Madagascar introduces readers to the fascinating and diverse ant fauna of the Afrotropical and Malagasy regions. Featuring illustrated keys to subfamilies, separate keys to Afrotropical and Malagasy ant genera, and distribution maps, it also describes diagnostic characters, explores ant ecology and natural history, and includes a list of all currently recognized ant species in the regions. This detailed guide is an essential tool for entomologists and myrmecologists working with and learning about this diverse population of Formicidae.

Product Details

ISBN-13:	9780520962996
Publisher:	University of California Press
Publication date:	07/26/2016
Sold by:	Barnes & Noble
Format:	eBook
Pages:	512
File size:	120 MB
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About the Author

Brian L. Fisher is curator at the California Academy of Sciences in San Francisco and adjunct professor at the University of California, Berkeley. 
 
Barry Bolton was formerly a myrmecologist at the Natural History Museum, London (1971–2004). He is now retired from the museum and works as an independent researcher.

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Ants of Africa and Madagascar

A Guide to the Genera

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By Brian L. Fisher, Barry Bolton, Jessica Huppi

UNIVERSITY OF CALIFORNIA PRESS

Copyright © 2016 The Regents of the University of California
All rights reserved.
ISBN: 978-0-520-96299-6

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CHAPTER 1

FAMILY FORMICIDAE

The Ants

All ants are contained within the single family Formicidae within the Aculeata, which is a monophyletic group of families within the monophyletic suborder Apocrita, of the order Hymenoptera (Gauld and Bolton, 1988; Goulet and Huber, 1993). The family is defined by a unique combination of biological and morphological traits, which is given here. In recent years a number of molecular phylogenies that span the whole family have been produced. Notable among these are Moreau, et al. (2006); Brady, et al. (2006); Ouellette, Fisher, and Girman (2006); Moreau (2009); and Moreau and Bell (2013). Phylogenetic studies that deal in detail with single subfamilies are mentioned in the introductions to the subfamilies concerned. A useful overview of ant phylogeny and classification has been published by Ward (2007), and Bolton (2003) provided the most recent morphological analysis of all the subfamilies.

Family FORMICIDAE Latreille, 1809

BIOLOGY: The vast majority of ants can easily be recognized because they are eusocial hymenopterous insects that have a wingless worker caste, and their colonies persist for more than one season, usually producing a new generation of reproductives (queens and males) annually. Alate sexual forms engage in mass nuptial flights, and the wings of alate queens are deciduous and shed after mating.

MORPHOLOGY: Hymenoptera Aculeata with the following combination of characters:

The head is prognathous.

An infrabuccal sac is present between the labium and the hypopharynx.

The antenna is geniculate between the elongated first segment (the scape) and the remaining segments together (the funiculus).

The antenna has 4–12 segments in female castes, and 9–13 in males.

A metapleural gland is usually present in the female castes.

Abdominal segment 2 forms a differentiated petiole; it is always isolated from the mesosoma by a constriction and an articulation, and there is almost always a constriction between it and the following segment (A3).

In the forewing of alate sexual forms, the cross-veins 3rs-m and 2m-cu are always absent.

SEXES AND CASTES: All ant species have 2 sexes, female and male — the former of which has a diploid chromosome number, the latter a haploid chromosome number, as in all Hymenoptera. In the overwhelming majority of ant species, the female sex is divided into 2 castes: a wingless worker (ergates) caste, with a relatively simple mesosoma, and an alate (winged) queen (gyne) caste in which the mesosoma, as well as bearing wings when virgin, has a greater number of mesosomal sclerites. Queens that have mated and shed their wings may continue to be referred to as alate, reflecting their original appearance, or be called dealate.

There are, however, numerous exceptions to this general rule. The worker caste is usually monomorphic, of a single form where all the workers of a colony are morphologically alike, but in some genera the workers may be dimorphic (of 2 different forms) or polymorphic (of 3 or more different forms). In polymorphic forms the workers of each morph may be distinct, but usually their morphologies form a continuous sequence of structural modification — from smallest (usually the simplest) to largest (usually the most specialized). In a relatively few genera, workers take over the role of reproductives in the colony, where they are called gamergates. In these societies no queen is present, the caste having been abandoned. In advanced socially parasitic species, the worker caste may be entirely lost.

The queen caste is usually easily distinguished from the worker, but in some genera the queen never develops wings, has the overall appearance of a worker, though often larger, and is termed an ergatoid (worker-like) queen. Most species have either one or the other form of queen, but in some species a colony may contain both alate and ergatoid queens. Even less commonly, some species have both alates and ergatoids, as well as one or more intercastes — forms that are morphologically intermediate between the alate and the ergatoid forms. Conspicuous among the nomadic, mass predatory taxa of the Dorylinae is a monstrous ergatoid queen with very modified morphology, termed a dichthadiigyne.

The male is usually alate, and this sex is only rarely subdivided into separate castes, but in some species wingless worker-like males are produced, termed ergatoid males. These ergatoid males may replace the usual alate males or may exist together with them in a single species. Extremely rarely, the ergatoid male caste is present as 2 discrete subcastes.

In the part of the book that details the individual genera, comments are included for those with peculiar reproductive forms, but the majority (those with a monomorphic worker, alate queen, and alate male) are not specially mentioned. The definitions of subfamilies and genera in the text are based on the worker caste. This is because it is the most numerous and commonly encountered caste, present year-round both within and outside of colonies. Queens, on the other hand, are usually restricted to a single individual, always concealed within a colony, and males are transient, only produced once each season and not leaving the nest until the time of the nuptial flight, after which they soon die. There are a number of genera in which the males remain unknown, and many in which the number of recorded queens falls far short of the actual number of known species. As a consequence, almost all morphology-based ant taxonomy depends on the workers. In recent years some effort has been made to increase the numbers of known males, but this endeavor is far from complete.

AFROTROPICAL AND MALAGASY SUBFAMILIES

The family Formicidae is currently divided into 17 extant subfamilies and 4 that are wholly extinct. In the regions under consideration here, 11 extant subfamilies occur. Present in both the Afrotropical and the Malagasy regions are 8 subfamilies, including the world's 4 largest subfamilies Formicinae, Dolichoderinae, Myrmicinae, and Ponerinae together with the 4 smaller subfamilies Amblyoponinae, Dorylinae, Proceratiinae, and Pseudomyrmecinae. In addition, the Afrotropical region has representatives of 3 very small subfamilies (Agroecomyrmecinae, Apomyrminae, and Leptanillinae) that do not occur in the Malagasy region. Of the 6 subfamilies that are entirely absent from the Afrotropical and the Malagasy regions, Martialinae and Paraponerinae are both monotypic and restricted to the Neotropical region. Aneuretinae, another monotypic group, is found only in Sri Lanka, although it has an extensive fossil record, and Myrmeciinae is almost entirely restricted to Australia. The final 2 subfamilies both exhibit a mainly Gondwanic distribution. Heteroponerinae occurs in the Neotropical and Austral regions, with a strange isolated genus in the Palaearctic. Ectatomminae has mainly the same distribution but also extends into the Malesian (Indo-Australian) and Oriental regions, with a few species penetrating the southern Nearctic.

The subfamilies of Formicidae that occur in the Afrotropical and Malagasy regions together are identified below in a single dichotomous key. This is followed by comments and morphological definitions concerning each subfamily, in alphabetical order. Definitions of specialized anatomical terms encountered in the key are given in the morphological glossary at the end of the book.

Key to Afrotropical and Malagasy Subfamilies (Workers)

1a Body with a single isolated or reduced segment (A2 = petiole) between the mesosoma and gaster (A); A3 is either entirely confluent with A4 (B) or is separated from it by a girdling constriction (C); if the latter, then A3 is not markedly reduced in size with respect to A4.....2

1b Body with 2 isolated or distinctly reduced segments (petiole and postpetiole = A2 and A3) between the mesosoma and gaster (AA); either both segments are much reduced or the second is somewhat larger than the first, but if the latter, then A3 is distinctly very much smaller than A4 (DD)..... 8

2a (1) Apex of abdomen with a semicircular to circular orifice, the acidopore, formed from the hypopygium (A). This structure often projects as a nozzle that is fringed with setae, but sometimes there is no nozzle or setae, and the acidopore is overlapped by the pygidium when not in use (becomes visible if the sclerites are separated); in this latter condition, the antennal sockets are located well behind the posterior clypeal margin. Sting absent.....Formicinae

2b Apex of abdomen with hypopygium lacking a semicircular to circular acidopore (AA). Sting present or absent; when present, it is usually easily visible, but when reduced or vestigial (or sometimes if present but completely retracted), the hypopygium has a smooth posterior margin and the antennal sockets abut the posterior margin of the clypeus.....3

3a (2) With head in ventral view and mouthparts closed, the prementum is not visible; it is entirely concealed by the labrum anteriorly and the maxillary stipites on each side; the stipites meet along the midline (A). Metapleural gland orifice overhung and concealed from above by a cuticular lip or flange. Spiracles on the tergites of A5–A7 exposed, not overlapped and concealed by the tergites of the preceding segments (B).....Dorylinae (part)

3b With head in ventral view and mouthparts closed, the prementum is clearly visible; it is bounded by the labrum anteriorly and the maxillary stipites on each side of it (AA). Metapleural gland orifice not overhung and concealed from above by a cuticular lip or flange. Spiracles on the tergites of A5–A7 overlapped and concealed by the tergites of the preceding segments (BB).....4

4a (3) Tergite of the helcium with an extensive U-shaped or V-shaped emargination dorsally in its anterior margin, easily visible if the gaster (= A3–A7) is slightly depressed from the petiole (A2) (A). Sting vestigial or absent, in any case the vestiges not detectable without dissection.....Dolichoderinae

4b Tergite of the helcium entire, its anterior margin dorsally without a U-shaped or V-shaped emargination (AA). Sting present and functional, often projecting in dead specimens; in many species the sting shaft is visible through the cuticle of the abdominal ventral apex, even when it is fully retracted.....5

5a (4)Promesonotal suture absent from the dorsum of the mesosoma (A).....Proceratiinae

5b Promesonotal suture fully developed across the dorsum of the mesosoma, articulated, the suture flexible in fresh specimens (AA).....6

6a (5)Antennal sockets entirely exposed in full-face view (A). Labrum with numerous peg-like dentiform setae arranged in transverse rows (B). A transverse sulcus present across the sternite of A3 posterior to the helcium (C).....Apomyrminae

6b Antennal sockets partially to entirely covered by the frontal lobes in full-face view (AA). Labrum without transverse rows of peg-like dentiform setae (BB). Sternite of A3, posterior to the helcium, without a transverse sulcus (CC).....7

7a (6) Petiole (A2) very broadly attached to A3, so that in profile the petiole does not have a free, descending posterior face (A). Helcium in profile with its dorsal surface projecting from very high on the anterior face of A3, so that above the helcium A3 has no free anterior face (B). Orifice of the metapleural gland is directed prodominantly dorsally and posteriorly, on a curved surface mesad of a posterolateral swelling or plate.....Amblyoponinae

7b Petiole (A2) narrowly attached to A3, so that in profile the petiole has a distinct free, descending posterior face (AA). Helcium in profile with its dorsal surface projecting from the midheight or lower on the anterior face of A3, so that above the helcium A3 has a free anterior face (BB). Orifice of the metapleural gland a simple hole, directed laterally or posteriorly, not on a curved surface mesad of a posterolateral swelling or plate.....Ponerinae

8a (1) Eyes present and usually conspicuous, composed of 1 to many ommatidia (A)....9

8b Eyes entirely absent (AA).....11

9a (8)Eyes located at the extreme posterolateral corners of the head, at the posterior apex of a broad, shallow scrobe (A). First gastral segment (A4) with tergosternal fusion, the tergite massively hypertrophied and ball-like, the sternite extremely reduced (B). Segments A5–A7 reduced and telescoped within A4, together directed anteriorly. Metapleural gland orifice opens laterally.....Agroecomyrmecinae (genus Ankylomyrma only)

9b Eyes not located at the extreme posterolateral corners of the head, not at the posterior apex of a broad shallow scrobe (AA). First gastral segment (A4) with the tergite and sternite not fused, the tergite not ball-like, the sternite not reduced (BB). Segments A5–A7 not reduced, not telescoped within A4, not directed anteriorly. Metapleural gland orifice opens directly laterally or is a narrow slit on the side of the sclerite.....10

10a Promesonotal suture conspicuously present and fully articulated across the dorsum of the mesosoma (A). Metapleural gland orifice simple, opening directly laterally, the orifice conspicuous and located immediately above the lower margin of the metapleuron. Metatibia with 2 spurs (anterior may be very small) (B). Pretarsal claw of hind leg with a preapical tooth present on the inner curvature (may be difficult to see in small species) (C).....Pseudomyrmecinae (genus Tetraponera only)

10b Promesonotal suture usually absent across the dorsum of the mesosoma, but sometimes a weak impression or a narrow, fully fused transverse line can be seen (AA). Metapleural gland orifice a longitudinal slit or narrow crescent that opens dorsally to posterodorsally and is located on the side, well above the lower margin of the metapleuron (slit may be very narrow and difficult to see). Metatibia with 0–1 spur (BB). Pretarsal claw of hind leg simple, without a preapical tooth on the inner curvature (CC).....Myrmicinae (part)

11a (8) Promesonotal suture conspicuously present across the dorsum of the mesosoma, deeply impressed and fully articulated (A). Propodeal lobes absent (B). Pygidium large and conspicuous. (C).....Leptanillinae (genus Leptanilla only)

11b Promesonotal suture absent across the dorsum of the mesosoma(AA). Propodeal lobes present (BB). Pygidium small and inconspicuous (CC).....12

12a (11) Metatibial gland present: apical half of ventral surface of metatibia with an elongate impression or area of extremely thin translucent cuticle (A). Metapleural gland orifice opens laterally but is overhung from above by a flap of cuticle. Antennal sockets very close to the anterior margin of the head, always fully exposed; frontal lobes entirely absent (B). Parafrontal ridges present (C). Antenna with 10 segments.....Dorylinae (part; genus Aenictus)

12b Metatibial gland absent: apical half of ventral surface of the metatibia without an elongate impression or an area of extremely thin translucent cuticle. Metapleural gland orifice a longitudinal slit or narrow crescent that opens dorsally to posterodorsally (may be difficult to see). Antennal sockets well behind the anterior margin of the head; frontal lobes present that partially to entirely conceal the antennal sockets in full-face view (BB). Parafrontal ridges absent(CC). Antenna with 4–12 segments.....Myrmicinae (part)

Subfamily Accounts

AGROECOMYRMECINAE Carpenter, 1930

INTRODUCTION: Agroecomyrmecinae is a very small subfamily that until now has contained only the monotypic extant Neotropical genus Tatuidris Brown and Kempf together with 2 fossil genera, Agroecomyrmex Wheeler, W.M., from the Eocene Baltic Amber, and Eulithomyrmex Carpenter from the Oligocene of the USA. To these, the Afrotropical genus Ankylomyrma was recently transferred here from Myrmicinae based on molecular phylogenetic analysis (Ward, et al. 2015).

Following a full dissection of the worker of Ankylomyrma by one of us (Bolton), it became clear that the genus certainly did not belong in Myrmicinae, as it differs from the uniform morphology of all members of that very large subfamily in terms of structure of the torulus, form of the metapleural gland orifice, very different structure of the helcium, and complete tergosternal fusion of A4. The establishment of a separate subfamily to contain this genus, based on the tribe name Ankylomyrmini proposed by Bolton (2003), was considered, but the publication by Ward, et al. (2015) of DNA analyses of myrmicine genera indicated the close affinity of Ankylomyrma with Tatuidris. The new definition that follows applies to both extant representatives of the subfamily, and the characters of both are compared for clarity; some other characters are noted under the definition of Ankylomyrma. Although the differences seem great, their range is in fact no greater than is exhibited by the various genera of Myrmicinae. However, it is probably best to regard the subfamily as having 2 tribes, based on the differences noted here: Ankylomyrmini Bolton (2003), containing only the arboreal Afrotropical Ankylomyrma coronacantha, and Agroecomyrmecini Carpenter (1930), which contains Tatuidris and the fossil genera mentioned above.

(Continues...)

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Table of Contents

Contents

Acknowledgments,
Introduction to the Ant Genera,
Introduction Plates,
Family Formicidae: The Ants,
Afrotropical and Malagasy Subfamilies,
Key to Afrotropical and Malagasy Subfamilies (Workers),
Subfamily Accounts,
Afrotropical and Malagasy Genera,
Key to Afrotropical Genera (Workers),
Key to Malagasy Genera (Workers),
Genus Accounts,
Glossary,
References,
Index,
Genus Plates,