Corresponding author: Alice Laciny (
Academic editor: Michael Ohl
Species of
Within the eight recent genera of the tribe
During our ongoing revision of the
We herein present morphometric data on the Asian species
Coll. H. Zettel, Vienna, Austria
Sk. Yamane Collection, Korimoto, Japan
Thailand
We measured specimens from most parts of the distribution area of
Examined specimens were either pinned or dry mounted on card squares or triangles. Examination and measurements of specimens were carried out with a Nikon SMZ1500 binocular microscope at magnifications of up to 256×.
Total length
Head width
Head length
Head size
Eye length
Scape length
Mesosoma length
Petiole height
Petiole length
Node height
Femur length
Length of maxillary palp segment 5, measured from base to apex
Length of maxillary palp segment 6, measured from base to apex
Cephalic index
Scape index
Eye Index
Petiole Index
Femur Index
Palp Segment Index
All measurements are in millimetres and separated by caste. Due to the condition of some specimens, not all measurements were taken from all animals. Measurements of minor workers include the holotype (plotted separately in Figs
Digital photos were taken with a Leica DFC camera attached to a Leica MZ16 binocular microscope with the help of Leica Application Suite V3, and stacked with ZereneStacker 64-bit. Processing of images was performed with Adobe Photoshop 7.0.
Measurements: alate gynes (n = 5):
We used two measurements to describe body size, total length (
Distribution of mesosoma length total length
Measurements: alate gynes (n = 5):
head size
Distribution of mesosoma length head size
Distribution cephalic index
The three castes differ considerably in head shape (Figs
Measurements: alate gynes (n = 5):
Eye size in minor workers is strongly correlated with body size (
Distribution of eye length mesosoma length
In minor workers the eyes are dorsolaterally located, close to the lateral outline of the head in frontal view (Fig.
Minor workers do not possess ocelli or other structures in their place. In one major worker from Myanmar we observed three reduced ocelli, whereas many other majors have small depressions or scars at these positions.
The clypeus is similarly shaped in major and minor workers, whereas the medial protrusion is slightly longer in gynes (Figs
The mandibles of majors are much stouter than those of minors, especially in the basal half. The mandibles of gynes are of intermediate shape.
Measurements: alate gynes (n = 3):
The maxillary palpi of minors are much longer in relation to
Distribution of maxillary palp segment index
Measurements: alate gynes (n = 4):
The antennae of majors and gynes are relatively shorter and thicker than those of minors. The scape index (
Distribution of scape index
Distribution of scape length mesosoma length
The mesosoma of majors is slightly more robust (wider and higher) than that of minors, though no morphometric data were recorded except
Measurements: alate gynes (n = 5):
We measured the length of the hind femur (
Distribution of femur index
Measurements: alate gynes (n = 5):
No evident differences were observed when comparing the gasters of minor and major workers. Due to the presence of reproductive organs, gynes possess a larger gaster relative to the rest of the body, but without apparent structural differences compared to the other castes.
The specimens from Borneo consistently differ from the rest of the examined material by the length of their appendages (maxillary palpi, antennae, and legs; Figs
Distribution of femur length mesosoma length
The examined gyne and minors of
All examined
The results of our morphometric analyses show that
Perhaps the most striking difference between the two worker subcastes is in the shape of the head, which is narrow and ovate with a well-developed collar in minors, but greatly enlarged, heart-shaped and without collar or margin in majors (Figs
When comparing mesosomal architecture between castes, both major and minor workers possess a well- developed prothorax which is slightly enlarged in majors, whereas the mesothorax is greatly hypertrophied in gynes (Fig.
A recent study focusing on morphological variation in a species of the
The results of this study show a clear worker dimorphism and a conspicuously broad size range of minors, which is apparent in intraspecific as well as intracolonial comparison. It is therefore a valid assumption that
The high nutritional investment necessary for producing a distinct soldier subcaste suggests that these animals must serve a function greatly beneficial to colony survival and fitness (
Altogether the results obtained within this study and their comparison to trends observed in the COCY clade (Laciny et al., in prep.) and other previously studied species (e.g.,
Examined specimens from Borneo clearly differ from specimens from other localities by proportions of appendages, colour pattern and setae.
We thank the following collection curators for loans of specimens or access to collections under their care: Bui Tuan Viet (
Table S1: Measurements (mm) of all examined specimens of
specimens data