Colobopsis macarangae

This species nests in the myrmecophytic plant Macaranga lamellata in undisturbed forests in Sarawak. The plants provide domatia for nesting and produce food bodies. The ants also tend Coccus species on the plant. A second ant species (Crematogaster) sp., also inhabitats this plant but only one nest of one of these species is found on any given plant.

Identification
Maschwitz et al. (1996) - No soldier caste.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia.

Biology
Maschwitz et al. (1996) – This species, and an Crematogaster species both inhabit Macaranga lamellate trees. Crematogaster colonies were intermingled with Colobopsis-inhabited plants across a few study plots.

Colony structure, ant behavior and plant-ant characters. Larger Colobopsis macarangae colonies always contained only one queen indicating monogyny in this species. As a rule, the females were found in the youngest internodes of the tree, in contrast to all Macaranga-Crematogaster associations, where they are usually found in the lower, older pans of the stem. The Crematogaster workers completely hollow out the compact interior of the nodes creating an uninterrupted passage inside the stem. In contrast, the Colobopsis workers produce many partly-separated chambers in the stem interior with help of incomplete septa built our of carton material. Although the older internodes become hollow by themselves through pith degeneration, the youngest pith-containing internodes were observed to be hollowed out by the workers from the outside. In the Colobopsis-association, and in contrast to the Crematogaster-systems, the workers closed the older lower entrance holes with carton (subsequently fully closed by plant growth) and keep open only two or three entrances in the youngest internodes are the apex of the sterns (a similar phenomenon was reported for Colobopsis quadriceps on Endospermum myrmecophilum in Australia (Monteith & Wood 1987). Colobopsis as well as Crematogaster workers were observed collecting foodbodies.

In rather young and small colonies, winged sexuals (alates) were found. Males were found in a 2.5 m tall tree, a queen-right colony was found with fewer than 100 workers, and female pupae were found in a slightly larger colony in a 5 m tall tree. The development of alates in small colonies is typical of highly-developed myrmecophytic ants, which need a frequent and high output of sexuals for rapid and complete colonization of new, strongly scattered host tree saplings (unpublished data). We have no data on the foraging behavior of Colobopsis-workers and do not yet know whether they are exclusively restricted to their host trees.

When aggravated by humans the workers of larger colonies attacked readily by biting. At this they released a strong, highly characteristic and pleasant smell of a citral-like terpene from their mandibular glands, probably as defense and/or alarm secretion. Actually, the type of ant-colonization of a tree can be easily detected by this odour. We do not yet know about the protective behavior of the ants, how workers behave against herbivores or against plant competitors such as climbers, or whether they clear the plant surface of epiphyllae or herbivore eggs. In two young plants, 1 and 1.2 m tall, which were observed for a few hours, workers were most common on the youngest leaf. When we checked the leaves every 30 minutes between noon and l5:00, on average 30 workers were counted on the youngest large leaf and on average three on the older leaves.

Colony foundation of Colobopsis macarangae. Searching behavior and domatium penetration of the young queen, was not observed directly. The weak pigmentation of both females and males of Colobopsis macarangae suggest that swarming, mating, host plant search and colonization take place during the night, as happens in Crematogaster species associated with Macaranga. Searching behavior and host plant recognition is thought to be a highly exact process. In one of the study sites the number of young plants suitable for colonization, was rather small. In an area of about 2 ha we detected only two young M. lamellata plants, nevertheless both were colonized by queens.

Many colony foundations were observed in all stages of development but most of them had not been successful (40 out of 49). One sapling, 70 cm tall, contained the remains of 15 colony-founding (Colobopsis females, and in another sapling, 40 cm tall, 7 dead queens and one live queen (still in a closed chamber), were found. In both saplings a larger living colony, with many workers was also present, suggesting that the most probable explanation for the dead queens is intraspecific competition, as is observed in Macaranga-Crematogaster associations (Fiala & Maschwirz, unpublished data). In the case of (Colobopsis macarangae the succcesful colonies (with queens) appear to have moved to the youngest internodes via the plant surface, based on the observation that no open holes were present in the lower parts and that the hollow internodes were not connected.

According to our observations on different stages of colony foundation, the arriving queens must bite a hole in a young internode, then close the hole with pith remains before laying eggs. The foundation entrance hole soon begins to close by growth and finally has to be reopened when the first workers have eclosed. The first workers are nurtured by the queen from her body resources. These workers are smaller than those of larger colonies, which is a typical feature of claustral colony-founding ants. In two closed chambers we found single queens with 2 and 3 worker pupae respectively, in the latter together with 3 eggs. Very young colonies apparently do not fight seriously, as indicated by the coexistence of two open colonies with a few workers on a single plant. This seems to happen later when more and larger workers start being active on the surface.

Scale insects. Scale insects were found in 46% of the larger (more than 20 workers) Colobopsis macarangae colonies in the primary forest (n = 13). The number of scale insects per tree was variable. The species was identified as Coccus macarangae (H. Heckroth, pers. comm.), a species frequently found in Macaranga-Crematogaster associations (unpubl. results).

In the association of Crematogaster with M. lamellata, 65% of the 30 plants studied contained coccids. Coccus macarangae was however quire rare. In the logged area, the most frequent species was a newly detected soft scale, Coccus sp. 84, which was abundant in Lambir and occurred in four other Macaranga species in the study area. Other coccids included C. penangenis, C. secretus and C. tumuliferus.

Young queens were never found with coccids during their fully claustral colony foundation in either Colobopsis or Crematogaster associations. Coccids must therefore arrive later as crawlers by wind and get access to the colonies either actively and/or by the workers collecting and carrying them into the domatium.

Nomenclature

 *  macarangae. Camponotus macarangae Dumpert, 1996: 38, fig. 5 (w.q.m.) BORNEO. Combination in Colobopsis: Ward, et al., 2016: 350.

Worker
Holotype. TL 3.9, WL 1.25, PW 0.64, HL 1.15, HW 1.02, CI 88.7, SL 0.82, SI 124, OD 0.25 or 0.24 HW.

Head longer than wide (CI 88.7). HW nearly as large at the mandibles as near the occipital margin. Sides of the head weakly, occipital margin strongly rounded. Eyes are situated within the upper third of the head. Frontal carinae extend from the lower to the upper third of headlength. Apart from a slight indentation near the scapal insertion, the fro mal carinae are straight. Clypeus nor carinated and as long as wide (0.46 x 0.46 mm). Frontal area not visibly delimited and as much shiny as surroundings. Anterior clypeal margin considerably rounded. Mandibles short and slender, with lateral borders weakly curved and five unequal teeth on each masticatory border. The two apical teeth stronger than the remaining three. Antennal scapes relatively short, projecting beyond the occipital margin by about one fifth of their length. Apical flagellar segments slightly thickened.

Alitrunk with slight impression between promesonotum and propodeum. Pro- and mesonotum not marginated, propodeum rounded, showing neither margins nor thorns. Promesonotum, seen in profile, broadly rounded and higher than propodeum. Propodeal profile considerably flattened on top. Petiole with a broad base, tapering towards the apex into a blunt ridge. Seen from behind, petiolar apex is broad and notched.

Colour black to blackish brown. Mandibles, clypeus and the end of the gaster slightly lighter. Tarsi of the legs yellowish brown. Surface of head, alitrunk and gaster shiny. SEM-photograph reveals no special cuticular structures on head and alitrunk and only scarce decumbent pubescence. Gaster with weak decumbent pubescence. Longer erect and suberect hairs especially on clypeus, but also on rest of head, alitrunk and gaster.

Workers of this species are monomorphic to a large extent: variations in size are very small.

Paratypes: TL 3.7 + 0,25 (standard deviation), WL 1.23 + 0.1, PW 0.7 + 0.045, HL 1.1+ 0.1, HW 0.99 + 0.08, CI 90 + 1.2, SL 0.78 + 0.07, SI 125,1 + 7,5, OD 0.25 + 0.02 or 0.24 + 0.05 HW (measurements of 21 specimens).

Queen
Head considerably longer than wide (CI 85 + 1.1). Near the mandibles head nearly as wide as near the occipital margin (Fig. 5b). Sides of the head and occipital margin slightly convex. Eyes distinctly larger than those of workers and situated behind midlength of the sides of the head. Ocelli prominent, distance between ocelli 0.25 and 0.20 mm, respectively. Distance between ocelli and compound eyes 0.4 mm. Frontal carinae extend from the lower to the upper third of headlength. Apart from a slight indentation near the scapal insertion, they are straight and slightly divergent. Frontal area not visibly delimited and as much shining as surroundings. Clypeus not carinated and as long as wide (0.54 x 0.54 mm). Anterior clypeal margin nearly straight only slightly convex - with small median excision. Mandibles strong, distinctly rounded on outside and with five unequal teeth on inside. The two apical teeth stronger than the remaining three. Antennal scapes relatively short, projecting beyond the occipital margin by about one fifth of their length. Apical flagellar segments slightly thickened. Petiole with a broad base, tapering toward the apex into a narrow ridge, when seen from the side. Seen from behind, the petiolar apex is broad and nearly straight, showing a very weak notch.

Whole body shiny, covered sparsely with fine decumbent pubescence. Longer erect and subnerect hairs on whole body, especially on front parts of head and on mandibles. Head dark brown with lighter front parts and antennae, eyes black. Rest of body-yellow brown, kegs darker.

Paratypes (9): TL 5.8 ± 0,35 (standard deviation), WL 2.05 ± 0.15, PW 1.15 ± 0.20, HL 1.42 ± 0.1, HW 1.2 ± 0.08, CI 85 ± 1.1, SL 0.97 ± 0.06, SI 123 ± 8, OD 0.52 ± 0.01 or 0.43 ± 0.05 HW.

Male
Head with nearly parallel sides (not trapezoidal) and distinctly longer than wide (CI 87.4). Eyes prominent, extending to the upper end of head sides. Occipital margin strongly convex with protruding ocelli. Clypeus broad (width 0.27 mm) and weakly delimited from surrounding head parts. Anterior clypeal margin rounded (convex). Short frontal carinae divergent, reaching hack to upper third of head. Eyes very large: maximum diameter 0.38 mm or 0.5 HW. Mandibles strong and weakly rounded on the outside; inside armed with four teeth, one strong apical and three subequal rounded ones. Scapes short, projecting only slightly beyond occipital margin of head. Pedicel expanded at its distal end and thicker than following flagellar segments. Apical flagellar segments not thickened. Petiolar scale triangular in profile with a broad base tapering to a blunt ridge. Ridge with a deep median excision. Whole body shiny. Head in most parts brown, mandibles and front parts of head - as well as antennae- yellow-brown. Rest of body, including legs, yellow to yellow-brown. Wings whitish with yellow veins. Decumbent pubescence sparse on whole body; higher erect and suberect hairs denser, especially on head and alitrunk.

Paratypes (9): TL 4.2 ± 0.35 (standard deviation), WL 1.75 ± 0.15, PW 0.88 ± 0.15, HL 0.84 ± 0.04. HW 0.75 ± 0.03, CI 88.9 ± 3.5, SL 0.6 ± 0.05, SI 131.6 ± 9.5. OD 0.37 ± 0.01 or 0.46 ± 0.05 HW or 0.51 ± 0.02 HW.

Type Material
Holotype: Borneo: Sarawak, Lambir-Park, living in Macaranga lamellata, Jan. 1994, U. Maschwirz leg. (Naturhistorisches Museum Basel)

Paratypes: 21 workers with same data as holotype and Borneo: Sarawak, Lambir-Park, living in M. lamellata, 9/22/1994, U. Maschwitz leg. , and Borneo: Sarawak, Lambir-Park, living in M. lamellata, 2/2/1994, U. Maschwitz leg. (2 in Museum of Comparative Zoology at Harvard University; 2 in collection of the Forest Research Institute of Malaysia (FRIM) in Kepong; 2 in Museo Civico di Storia Naturale, Genova; 15 in collection of the author)

Queen paratypes: Borneo: Sarawak, Lamhir-Park, living in Macaranga lamellata, Jan 1994, U. Maschwitz leg. and Borneo: Sarawak, Lambir-Park, living in M lamelatta, 9/22/1994, U. Maschwitz leg., and Borneo: Sarawak, Lambir-Park, living in M. lamellata. 2/2/1994, U. Maschwitz leg. (2 in Museum of Comparative Zoology at Harvard University; 2 in collection of the Forest Research Institute of Malaysia (FRIM) in Kepong; 2 in Museo Civico di Storia Naturale, Genova; 3 in collection of the author).

Male paratypes: Borneo: Sarawak, Lambir-Park, living in Macaranga lamellata, Jan 1994, U. Maschwitz leg. and Borneo: Sarawak, Lamhir-Park, living in M. lamellata, 9/22/1994, U. Maschwitz leg. , and Borneo: Sarawak, Lamhir-Park, living in M. lamellata, 2/2/1994 U. Maschwitz leg. (2 in Museum of Comparative Zoology at Harvard University; 2 in collection of the Forest Research Institute of Malaysia (FRIM) in Kepong; 2 in Museo Civico di Storia Naturale. Genova; 3 in collection of the author).

Etymology
The species name is derived from the fact that this species was exclusively found in Macaranga lamellata plants.