Crematogaster hova

Little is known about the biology of this species.

Identification
Blaimer (2010, 2012c) - A member of the Crematogaster hova group. Antennae 10-segmented then either: head and promesonotal sculpture deeply costulate (morphotype 4,3), or areolate (morphotype 5,3). Head and promesonotal sculpture reticulate to reticulate-areolate (morphotype 2,3) or aciculate (morphotype 1), and promesonotal suture incomplete, and mesonotum postero-laterally usually rounded or slightly tuberculate, rarely angular. I distinguish 5 morphotypes of workers within the C. hova-group on the basis of sculpture, body size and propodeal spines. Designation of these morphotypes is somewhat arbitrary as they are not entirely distinct from each other, but have intermediate forms.

Distribution
The C. hova-complex has a wide distribution throughout the humid and transition forests of northern, central and southeastern Madagascar. It is generally absent from the western dry deciduous and spiny forests occupied by C. grevei, but present in isolated pockets of humid or transition forest remaining at a few locations in the west, such as in e.g. P.N. Zombitse or P.N. Isalo. From the very northern tip to the extreme south of the island these ants are a prominent element of the rainforest canopy fauna, inhabiting all altitude levels, with a highest record of 2000m in the Marojejy massif. (Blaimer 2010)

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Biology
Blaimer (2010) - Within its distribution range, the Crematogaster hova-complex is the most abundant and dominant representative of the Malagasy Decacrema. Although these ants possess an arboreal lifestyle, they are nonetheless highly conspicuous on the forest floor when foraging for food and nesting material, and could hardly be missed in an inventory. Fisher et al. collected workers of these ants innumerable times from leaf litter and beating samples, as well as pitfall, yellow pan and malaise traps. Prevailing nesting behaviour of the C. hova-complex however is the construction of arboreal carton nests. I have found these nests in various heights in the canopy: from as low as 1.20 m, attached to vines or branches of young trees, to 20m or more high up in the crowns of canopy-level trees. The sizes of carton nests inhabited by workers, the reproductive queen and brood range from as small as 6 x 4cm in diameter to as large as 25 x 20 cm. Nests housing only workers are frequently encountered and can be smaller in size. It is unclear whether these queenless colonies represent satellite nests of larger nests that are hard to locate, or aggregations of workers whose colony underwent disturbances that resulted in the loss of their reproductive queen and brood. Polydomy in these carton-nesting colonies seems to be quite common, and two or more nests often can be found very close to each other on the same tree, or located on adjacent trees. Experimental or genetic studies would be needed to fully explore details of colony structure. In 17 carton nests out of a total of 30 dissected nests I found one dealate queen together with workers and brood, sometimes with alate queens and males as well. The remaining 13 nests contained only workers, sometimes together with brood. Carton nest colonies further housed staphylinid beetles (6 colonies), and in one case scale insects of an undetermined genus of the family Monophlebidae, possibly Gigantococcus (P.J. Gullan, pers. comm.).

There are some records in the CASC of C. hova-complex workers (in some cases with dealate queens) collected from dead twigs or branches, and in a single instance I have found workers with brood in a dead twig myself. It seems likely that colony founding within the species-complex takes place in dead twigs or branches and the construction of carton nests subsequently commences after a certain colony size is reached, i.e. when the colony can afford to send workers to forage for nest material rather than food. The ultimate domicile may always be the carton nest, since this can support much larger numbers of individuals and can be extended in size as the colony grows.

Nomenclature

 *  hova. Crematogaster hova Forel, 1887: 387 (w.) MADAGASCAR. Blaimer, 2010: 19 (q.). Combination in C. (Decacrema): Forel, 1910f: 9. Senior synonym of latinoda: Blaimer, 2010: 17.
 * latinoda. Crematogaster hova var. latinoda Forel, 1892k: 535 (w.) MADAGASCAR. Combination in C. (Decacrema): Wheeler, W.M. 1922a: 1026. Junior synonym of hova: Blaimer, 2010: 17.

Blaimer (2010) found this species is actually a species complex:

I distinguish 5 morphotypes of workers within the C. hova-complex on the basis of sculpture, body size and propodeal spines. Designation of these morphotypes is somewhat arbitrary as they are not entirely distinct from each other, but have intermediate forms – and further intermediate forms of these ‘intermediates’ exist. They should therefore not be perceived as distinct units, but rather as samples from an overall gradient. For the purpose of distribution mapping some ambiguous assignments to morphotypes were therefore made. The following distinction however simplifies the description of morphological variation greatly, and allows for its analysis for possible geographic patterns. Moreover, this morphotype concept presents a starting hypothesis for a much needed study on the population genetic level of the C. hova-complex.

Morphotype 1 (mt1). Small to large size (HW 0.83–1.10, WL 0.87–1.14). Head sculpture reduced aciculate to superficially areolate; propodeal spines medium size, at most as long as distance between their bases (SPI 0.21–0.28), in dorsal view only weakly diverging (<20º). Colour light brown to dark brown, less common black, metasoma often lighter coloured.

This morphotype conforms most closely with the C. hova and Crematogaster hova latinoda type specimens. C. hova latinoda type material has a petiole that is strongly broadened anteriorly with respect to C. hova.

Morphotype 2 (mt2). Medium to large size (HW 0.92–1.19, WL 0.93–1.22). Head sculpture reticulate, reticulate-areolate to weakly areolate; propodeal spines medium size, at most as long as distance between their bases (SPI 0.22–0.26), in dorsal view only weakly diverging (<20º). Colour light brown to black, metasoma often lighter coloured in brown form, 4th abdominal segment or entire gaster sometimes of yellow coloration (may be due to parasitism rather than inherent pigmentation).

This morphotype is intermediate in regard to mt1 and mt4. Morphotype 3 (mt3). Small to large size (HW 0.74–1.13, WL 0.78–1.19). Head sculpture from scattered aciculate to reticulate to costulate-areolate or areolate; propodeal spines large and robust, often “swollen” at base, at least as long or longer than distance between their bases (SPI 0.29–0.40), in dorsal view strongly diverging, ca. >30º from lateral margin of propodeum. Colour brown to black.

This morphotype conforms best with the C. ensifera type material.

Morphotype 4 (mt4). Medium to large size (HW 0.97–1.18, WL 1.01–1.21). Head sculpture deeply costulate to costulate-areolate; propodeal spines medium size (SPI 0.24–0.29), about as long as distance between bases or shorter, in dorsal view weakly or moderately diverging (<30º). Colour brown to black, more often black, sometimes gaster shows bi-coloration described for mt2.

This morphotype conforms closely to the C. schencki type material. Together with mt2 it is the most common morphotype of the hova-complex.

Morphotype 5 (mt5). Medium to large size (HW 0.96–1.13, WL 1.01–1.17). As mt4, except as follows. Head sculpture deeply areolate. Colour black.

Worker
Blaimer (2010) - Measurements (n=58). HW 0.74–1.19; HL 0.69–1.08; EL 0.15–0.27; SL 0.65–0.93; WL 0.78–1.22; SPL 0.19–0.44; PTH 0.15–0.24; PTL 0.22–0.38; PTW 0.22–0.39; PPL 0.14–0.23; PPW 0.20–0.33; LHT 0.64–0.97; CI 1.04–1.19; OI 0.18–0.29; SI 0.83–0.99; SPI 0.19–0.40; PTHI 0.52–0.86; PTWI 0.83–1.39; PPI 1.24–1.79; LBI 1.17–1.56.

Size highly variable, small to very large (HW 0.74–1.19, WL 0.78–1.22), commonly medium to large size.

Masticatory margin of mandibles with 4 teeth in smaller individuals, 5 teeth in larger specimens; posterior margin of head straight but sometimes medially depressed, laterally forming round or subangular corners; antennae with scapes reaching or surpassing posterior margin; midline of eyes situated at midline of head in full face view.

Pronotum laterally with distinct rounded or subangular shoulders; promesonotal suture incomplete, laterally impressed; outline of promesonotum in lateral view more or less rounded; dorsal face of mesonotum either flat or weakly convex, sometimes medially slightly raised over pronotum and rarely forming a small median tubercle anteriorly; lateral margin of mesonotum from rounded to slightly angular, sometimes bearing postero-lateral angular tubercules; length and divergence of propodeal spines variable; petiole highly variable; shape in dorsal view from weakly to strongly lobed, trapezoidal, hexagonal or suboval, in lateral view petiole usually tapering in height from posterior to anterior; subpetiolar process variable, either narrow to broad protuberance, with more or less angular tooth or absent, postpetiole in dorsal view from weakly to much wider than long (PPI 1.24–1.79).

Head sculpture variable; sculpture on mesosoma following mostly that on head, aciculate, reticulate, costulate or areolate; dorsal face of petiole mostly shiny, ventrally coarsely reticulate; postpetiole dorsally and laterally rugulose or reticulate, helcium carinulate; face with 4–6, sometimes up to 10 erect setae; 0–2, sometimes 4, rarely 6 erect-suberect humeral setae present on promesonotum; petiole and postpetiole devoid of long erect pilosity, sometimes shorter, suberect setae present on postpetiole.

Colour light to dark brown or black, sometimes dorsum of 4th abdominal segment yellow and gaster thereby bi-coloured.

Queen
Blaimer (2010) - Measurements (n=16) HW 1.60–1.97, HL 1.37–1.63, EL 0.43–0.53, SL 0.99–1.19, MSNW 1.22– 1.60, MSNL 2.36–2.67, SPL 0.02–0.13, WL 2.68–3.05, PTH 0.38–0.45, PTL 0.47–0.59, PTW 0.53–0.69, PPL 0.40–0.47, PPW 0.54–0.68, LHT 1.08–1.36 , CI 1.14–1.25, OI 0.29–0.37, SI 0.69–0.78, MSNI 0.52–0.66 , SPI 0.01–0.05, PTHI 0.70–0.91, PTWI 1.00–1.36, PPI 1.28–1.69, LBI 2.13–2.32.

Large to very large (HW 1.60–1.97, WL 2.68–3.05). With worker characters, except as described below.

Antennal scapes usually not surpassing posterior margin of head; midline of eyes situated at or slightly below midline of head in full face view; posterior margin of head straight or medially depressed.

Mesosoma broad and long (MSNI 0.52–0.66, WL 2.68–3.05); mesoscutum in dorsal view oval, less than half as wide as long; mesopleuron with episternal groove carinulate and usually ending in small pit just short of margin; in lateral view mesepisternum meeting pronotum at an oblique angle; postscutellum with posterior face distinctly flattened; propodeal suture weak, laterally not reaching level of propodeal spiracle; dorsal face of propodeum short, about one third of the size of posterior face; propodeal spines reduced, ranging from tubercule to denticles to very sharp points; petiole shape usually triangular, tapering from anterior to posterior margin, antero-ventral subpetiolar tooth absent.

Propodeum with horizontal carinulae on dorsal face; petiole dorsally more or less shiny, laterally and ventrally reticulate to costulate; postpetiole aciculate throughout; face with 10–20 short, erect setae, and otherwise abundant appressed pilosity; mesonotum with scattered erect pilosity, usually >20 setae, and abundant appressed pubescence; petiole laterally with short suberect pilosity, dorso-posterior erect setae absent; postpetiole with dorso-posterior erect setae present, further scattered suberect pilosity may be present; petiole and postpetiole with appressed pilosity throughout.

Colour light to dark brown, or black; metasoma usually lighter coloured.

Type Material
Blaimer (2010):

Crematogaster hova. Worker syntypes from Madagascar: Bois de l’Ivondro près de Tamatave (Dr.C.Keller), examined;. One worker syntype (CASENT0101804, top specimen of 3w on one pin) hereby designated the lectotype.

Crematogaster hova latinoda. Worker syntypes from Madagascar, Mangoroufer, Est Imerina (M.Sikora) [MHNG, examined]; Wheeler, 1922b:1026. Combination in C. (Decacrema). New synonymy.

Crematogaster schenki Forel,1891:182. Workers syntypes from Madagascar: Imerina: Antananarivo, Andrangoloaka (Rév. Père Camboué, Hildebrandt, Sikora) [MHNG, examined]. One worker syntype (CASENT0101748, top specimen of 2w on one pin) hereby designated the lectotype.

Crematogaster (Decacrema) ensifera. Worker syntypes from Madagascar: Forêts vierge de Sahana [MHNG, examined]. One worker syntype (CASENT0101790, middle specimen of 3w on one pin) hereby designated the lectotype.

Etymology
The C. hova-complex is named for the oldest available species name that belongs under the complex, Crematogaster hova Forel. The Malagasy word “hova” denotes the inhabitants of the region Imerina on the east coast of Madagascar, where the type locality of C. hova lies.