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Tapinoma incognitum
| Tapinoma incognitum | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Hymenoptera |
| Family: | Formicidae |
| Subfamily: | Dolichoderinae |
| Genus: | Tapinoma |
| Species: | T. incognitum |
| Binomial name | |
| Tapinoma incognitum Cover & Rabeling, 2024 | |
Tapinoma incognitum is a workerless inquiline that is only found within nests of its host, Tapinoma sessile. It is known from three collections that were made at the type locality on separate occasions. All were mixed colonies containing T. incognitum and its host. Each colony contained multiple fertile host queens, numerous host workers, and some host worker pupae. In addition, each nest contained males and females of T. incognitum, and, in two collections, parasite pupae. No T. incognitum workers were found. In each colony, several T. incognitum queens were observed with enlarged metasomas, implying that multiple parasite queens were reproductively active (i.e., functional polygyny of social parasite; Table 2). A striking feature of this species is the strong convergence in size and habitus between females and males (i.e., gynaecomorphism; Table 2). Males, however, are easily recognizable by their externally visible genitalia and because they are brachypterous; the wing remnants are small, crumpled, distorted, and persistent. In addition, T. incognitum also displays other morphological characters typical of the inquiline syndrome (Fig. 1, Table 2). Hallmark characters include reduced body size, the reduction of antennal segments in the males, and the reduction of palp segments in both queens (palp formula 4,3) and males (palp formula 5,3). The wings of queens are extremely fragile, easily deciduous, and almost certainly non-functional, and the males cannot fly. Thus, mating must take place in or around the nest.
Cover & Rabeling (2024) kept a colony alive for a few days and made some behavioral observations. It was eye-catching that the host workers carried social parasite queens as if they were pupae and the parasites retracted their appendages against their bodies and became pupae-like when carried. The host workers also regurgitated to and groomed the social parasite queens. Host and social parasite queens encountered one another often but seemed to ignore each other. This suggests that T. incognitum is well integrated in the host society. Collectively these morphological and life history traits indicate that T. incognitum is a workerless, host-queen-tolerant inquiline social parasite of T. sessile.
| At a Glance | • Workerless Inquiline • Brachypterous Male |
Photo Gallery
Cover & Rabeling (2024), Figure 1. Morphological comparison of the Tapinoma incognitum holotype queen A, C, E and a paratype male B, D, F in lateral A, B dorsal C, D and full-face E, F view. The type series was collected in Alumbed Hollow in Utah and belongs to a single nest series with the collection code SPC 7749. Scale bars: 0.5 mm (A–D); 0.2 mm (E, F).
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Identification
A workerless, host-queen-tolerant inquiline social parasite of Tapinoma sessile showing morphological and life history traits of the inquiline syndrome. Both females and males are miniaturized (i.e., smaller than the host workers), alate, and morphologically complete (Fig. 1, Table 2). Females eclose with intact wings, but the wings are fragile and quickly deciduous. Males are brachypterous. Females have a reduced 4,3 palp formula, anterior clypeal border with weak median concavity, denticulate mandibles with only 2–4 denticles. In side view petiole with low, rounded node; viewed from the rear dorsal margin concave (rarely flat). Males similar in size and overall habitus to females but often darker in color and easily recognized by their extruding genitalia. Males have a reduced 5,3 palp formula and only 12 antennal segments. Females of T. incognitum are closely similar in habitus to those of Tapinoma pulchellum, but can be easily distinguished by palp count, concave anterior clypeal border, mandibular dentition, and propodeal profile.
Keys including this Species
Distribution
Latitudinal Distribution Pattern
Latitudinal Range: 38.9° to 38.9°.
| North Temperate |
North Subtropical |
Tropical | South Subtropical |
South Temperate |
- Source: Cover & Rabeling, 2024
Distribution based on Regional Taxon Lists
Nearctic Region: United States (type locality).
Distribution based on AntMaps
Distribution based on AntWeb specimens
Check data from AntWeb
Countries Occupied
| Number of countries occupied by this species based on AntWiki Regional Taxon Lists. In general, fewer countries occupied indicates a narrower range, while more countries indicates a more widespread species. |
|
Estimated Abundance
| Relative abundance based on number of AntMaps records per species (this species within the purple bar). Fewer records (to the left) indicates a less abundant/encountered species while more records (to the right) indicates more abundant/encountered species. |
|
Biology
| Trait | Host | Social parasites | |||
|---|---|---|---|---|---|
| Tapinoma sessile | Tapinoma shattucki | Tapinoma inflatiscapus | Tapinoma incognitum | Tapinoma pulchellum | |
| Worker caste absent | – | + | + | + | ? (+) |
| Multiple egg laying host queens present (host polygyny) | + | ? (–) | – | + | ? |
| Multiple egg laying parasite queens present in host colony (parasite polygyny) | n/a | + | ? | + | ? |
| Parasite queen coexists with host queen (host queen tolerance) | n/a | ? (–) | – | + | ? (+) |
| Adelphogamy (inside nest mating) | – | ? (–) | ? | + | ? |
| Gynaecomorphism (gyne-like male morphology) | – | – | – | + | + |
| Fragmented populations, limited geographic distribution | – (North America) |
+ (2 localities in MA) |
+ (UT, CO) |
+ (type locality, UT) |
+ (type locality, NC) |
| Reduced body size | – | + (size of host worker) |
+ (size of host worker) |
+ (smaller than host worker) |
+ (smaller than host worker) |
| Exoskeleton becomes thinner and less pigmented | – | + | + | + | + |
| Number of antennal segments reduced in females | – (♀: 12) |
– (♀: 12) |
– (♀: 12) |
– (♀: 12) |
– (♀: 12) |
| Number of antennal segments reduced in males | – (♂: 13) |
– (♂: 13) |
– (♂: 13) |
+ (♂: 12) |
+ (♂: 12) |
| Number of maxillary and labial pals (palp formula) reduced in females | – (♀: 6,4) |
+ (♀: 5,4) |
+ (♀: 5,4) |
+ (♀: 4,3) |
+ (♀: 5,4) |
| Number of maxillary and labial pals (palp formula) reduced in males | – (♂: 6,4) |
+ (♂: 5,4) |
– (♂: 6,4) |
+ (♂: 5,3) |
+ (♂: 5,4) |
| Reduced mandibular dentition | – 14 teeth |
– (10–11 denticles) |
– (11 denticles) |
+ (2–4 denticles, plus apical tooth) |
+ (only apical tooth) |
| Reduced wings in females | – (♀ capable of flying) |
– (♀ capable of flying) |
– (♀ capable of flying) |
+ (♀: wings deciduous) |
– (♀: winged) |
| Reduced wings in males | – (♂ capable of flying) |
– (♂ capable of flying) |
– (♂ capable of flying) |
+ (♂: brachypterous) |
+ (♂: brachypterous) |
| Petiole thickened | – | – | – | + | + |
Cited Sources
- Cover, S.P., Rabeling, C. 2024. Four new inquiline social parasite species in the dolichoderine ant genus Tapinoma (Hymenoptera, Formicidae). ZooKeys 1202, 111–134 (doi:10.3897/zookeys.1202.120478).
- Kutter, H. 1968. Die sozialparasitischen Ameisen der Schweiz. Neujahrsblatt der Naturforschenden Gesellschaft in Zürich 171: 1–62.
- Prebus, M., Georgiev, B.B., van de Kamp, T., Hamann, E., Baker, I., Rabeling, C. 2023. The rediscovery of the putative ant social parasite Manica parasitica syn. nov. (Hymenoptera: Formicidae) reveals an unexpected endoparasite syndrome. Biology Letters, 19, 20230399 (doi:10.1098/rsbl.2023.0399).
- Rabeling, C., Messer, S., Lacau, S., do Nascimento, I.C., Bacci, M., Delabie, J.H.C. 2019. Acromyrmex fowleri: a new inquiline social parasite species of leaf‑cutting ants from South America, with a discussion of social parasite biogeography in the Neotropical region. Insectes Sociaux 66: 435–451 (doi:10.1007/s00040-019-00705-z).
- Wilson, E.O. 1971. The insect societies. Cambridge, Mass.: Harvard University Press. 548 pp.
Castes
Nomenclature
The following information is derived from Barry Bolton's Online Catalogue of the Ants of the World.
- incognitum. Tapinoma incognitum Cover & Rabeling, 2024: 115, fig. 1 (dq.m.) U.S.A. (Utah).
Type Material
Type locality. U.S.A., Utah, Sevier County, Alumbed Hollow, 8.4 miles west of I-70 (Exit 71) on Salina County Frontage Rd., a dirt road paralleling I-70. GPS: 38.910°N, 111.697°W; elevation 5980’ (1823 m). Small canyon running southwest to northeast with dense, heavily grazed Gambel Oak (Quercus gambelii) thickets to 25’ (8 m) tall on east-facing slope. Collected by SPC (SPC 7749), 16 July 2008. Collection Notes: SPC 7749. Site heavily grazed. Dense Gambel Oak thicket; forest floor protected from grazing by oak stem density. Superficial nest under rock in pale shade of dense Gambel Oak thicket. 2-cm thick oak litter present. Humusy sand soil. Very dry conditions. ~ 500 ants, multiple host queens present. Brood was mostly eggs and young larvae; just a few parasite and host worker pupae present.
Type material. Holotype queen (SPC 7749, MCZENT 00806456). Paratype male (SPC 7749, MCZENT 00806457), and the following additional paratypes: 13 queens, 17 males [16-VII-2008, SPC 7749]; 35 queens, 3 males [19-VII-2009, SPC 8077]; 19 queens, 4 males [19-VII-2013, SPC 8656]. Holotype and paratypes deposited in the MCZC. Additional paratypes deposited at CASC, CRC, LACM, and UCDC.