Colobopsis explodens

A member of the Colobopsis cylindrica group, a set of species that employ a novel defensive strategy. Minor workers of these so called exploding ants will, when threatened, flex their gasters so hard that they rupture. This releases a toxic chemical mixture that they then attempt to smear on their antagonists.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Brunei Darussalam, Malaysia. Oriental Region: Thailand.

Biology
Laciny et al. (2018) observed "a peculiar guarding behaviour: a small number of workers always stayed close to the entrance and seemingly monitored the entering and leaving of foragers. It is possible that an ant carrying a potential enemy as prey would be barred from entering the nest by guards within and must therefore present its gaster to be recognized as a colony member.

Colonies of Colobopsis explodens observed in Ulu Temburong National Park are commonly polydomous and polygynous. Colobopsis explodens frequently nests on dipterocarp trees and its colonies can contain thousands of individuals. The largest part of the studied colony lived on a 60 m tall Shorea johorensis Sym. (Dipterocarpaceae) tree. The colony’s foraging ground included the canopy of the main tree, its direct vicinity, and also covered canopies of a 25 m tall Horsfieldia wallichii (Hook.f. & Th.) Warb. (Myristicaceae) tree and a smaller tree of Shorea maxwelliana King (9 m). Colony fragments on all trees were connected by ant trails either through the canopy or on the forest floor in the litter layer. The total area occupied by the colony was estimated to be at least 2500 m2.

The colonies are distributed three-dimensionally, occupying any suitable nesting ground within the colony boundaries. On the main tree, we found four nesting sites of the examined colony in dead branches at heights ranging between 35 and 55 m above ground and two nesting sites in the living stem 50–60 m above ground. No nests in living branches were observed. At least five nest entrances were also seen in the stem of Shorea maxwelliana. No signs of necrosis of the plant tissue were observed around stem entrances.

The translocation of a nest fragment in a fallen branch to the laboratory’s terrace, 30 m away from its original location, resulted in the expansion of the colony’s foraging ground to a neighbouring Shorea sp. tree where these ants were not previously present, while the connection to the colony on the original host tree was maintained.

If provided with an appropriate artificial nest, Colobopsis explodens ants will inhabit it within several weeks up to several months and even use it to rear brood. One artificial nest, mounted on the main host tree, was colonized one week after it was installed. For the activity assessment, the easily accessible artificial nest #38 was observed. During behavioural monitoring, Colobopsis explodens was observed to be mainly diurnal, foraging between 6:00 and 18:00 hrs, with peak activity around 9:00 and 16:00 hrs. The activity correlated positively with the temperature with lowest values at 24.2 °C and highest at 28.6 °C. The atmospheric pressure and clouds did not influence the activity of Colobopsis explodens; humidity was constant over the period of observations ranging from 86 to 88%. A slight rain on a warm day did not reduce the activity of ants near the nest but no activity was observed during heavy rains. However, if a shelter was provided, Colobopsis explodens remained active also during the rain and even after sunset. A drastic reduction in the number of minor workers at the nest entrance was observed on the days of nuptial flight, when several alate gynes and males left the nest in the early evening. Between one and six minor workers (“guards”) were frequently positioned at the nest entrance, touching all incoming and outgoing workers with their antennae and seemingly monitoring the activity of foragers. In the early afternoon of the day with the highest activity, larvae were carried out of the nest. No carrying of larvae into the nest was ever observed.

Remarkably, during all observations the numbers of the minor workers leaving and entering the nest were almost equal. The fact that this proportion did not change over the day suggests a tendency to maintain a constant number of individuals present inside the nest.

After dusk, other species of Camponotini such as Polyrhachis spp., Camponotus spp., and Dinomyrmex gigas (Latreille, 1802) were observed on the trees in the vicinity of the artificial nest.

Within the colonies, minor workers were by far the most abundant caste of Colobopsis explodens, whereas major workers (soldiers) were rare and almost never seen outside the nest. Alate gynes and males were observed leaving the nest during nuptial flight after dusk on two occasions during our field observations. Several more alate sexuals were found inside a detached nest fragment. The same nest fragment also contained symbiotic ant crickets of the genus Camponophilus Ingrisch, 1995. Observations have shown that minor workers of Colobopsis explodens display a characteristic, possibly defensive pose with raised gaster (compare with Davidson et al. 2007) and are extremely prone to self-sacrifice when threatened. The mandibular gland content is released during autothysis by contracting the gaster until the integument ruptures, leading to the death of the ant. The secretion is slightly viscous, sticky, and has a species-specific bright yellow colour and a distinctive spice-like odour (Hoenigsberger et al., in prep.).

Minor workers of Colobopsis explodens spend significant time on leaves, which has previously been hypothesized to contribute to their nutrition (compare with Davidson et al. 2007, 2016). However, the exact purpose of their activity on leaves is yet to be understood. Observations suggest a patrolling or monitoring behaviour aiming at the removal of debris from the phyllosphere (mainly adaxial leaf surface but also abaxial leaf and petiole surfaces) and possible deterrence of intruding arthropods. Similar “cleaning” behaviour was observed in vitro, as well.

Another very specific behaviour was exhibited on the tree bark: Minor workers “graze” on the layers of epiphytes (mosses, lichens, algae, filamentous fungi, and yeasts) with their mandibles, often for up to 60 minutes. This behaviour differs from the cleaning behaviour on leaves and presumably contributes to the ants’ nutrition.

Preliminary feeding experiments using cultures of filamentous fungi isolated from the phyllosphere of the host trees remained unsuccessful, no fungal feeding was observed. Only a suspension of yeast in water was accepted in vitro (M. Rahimi, pers. obs.). However, minor workers of Colobopsis explodens have been observed to feed on small dead insects, fruit, and fish when offered on the foraging grounds (A. Kopchinskiy, A. Laciny & M. Hoenigsberger pers. obs.).

The molecular analysis of the mandibular gland (MG) content of Colobopsis explodens resulted in PCR amplification and sequencing of the 16S rRNA fragment of the bacteria Blochmannia sp. (Gammaproteobacteria), a genus of obligate symbiotic bacteria found in carpenter ants (Williams and Wernegreen 2015). We revealed four identical mOTUs originating from two different DNA extracts from samples composed of five pooled MG reservoirs of the minor workers each. The sequences of 728 nt were 99 % similar (11 SNP sites) to the “uncultured bacterium clone 193-11” KC136854 from Camponotus sp. voucher KC-A017-01 defined as Blochmannia sp. in Russell et al. (2012). More detailed data on autothysis, composition of mandibular gland secretion, biodiversity of the COCY-associated microorganisms, and experimental assessment of nutrition will be presented in future publications.

Nomenclature

 *  explodens. Colobopsis explodens Laciny & Zettel, in Laciny et al., 2018: 10, figs. 2-9 (s.w.q.m.) BRUNEI.

Worker
Holotype minor: TL 6.78; HW 1.48; HL 1.67; HS 1.58; PS5 0.23; PS6 0.25; EL 0.42; SL 1.33; SW 0.14; ML 2.05; HaL 0.15; PH 0.55; PL 0.47; NH 0.33; FeL 2.05. Indices: CI 88; SI 90; SWI 11; EI 29; PI 116; FeI 139; PSI 30.

Holotype minor: TL 6.78; HW 1.48; HL 1.67; HS 1.58; PS5 0.23; PS6 0.25; EL 0.42; SL 1.33; SW 0.14; ML 2.05; HaL 0.15; PH 0.55; PL 0.47; NH 0.33; FeL 2.05. Indices: CI 88; SI 90; SWI 11; EI 29; PI 116; FeI 139; PSI 30.

Paratype minor: (n = 59): TL 4.74–7.21; HW 1.22– 1.57; HL 1.30–1.78; HS 1.27–1.67; PS5 0.21–0.25 (20); PS6 0.20–0.26 (21); EL 0.33–0.43; SL 1.21–1.39; SW 0.11–0.16; ML 1.50–2.22; HaL 0.08–0.19; PH 0.41– 0.56 (44); PL 0.33–0.49 (47); NH 0.24–0.38 (52); FeL 1.73–2.10. Indices: CI 85–94; SI 87–104; SWI 9–12; EI 27–29; PI 112–133 (41); FeI 123–151; PSI 28–35 (20).

Head subovate, longer than wide, narrower anteriorly; sides posteriorly convex, posterior cephalic margin roundly convex; microstructure consisting of very fine, isodiametric or transverse mesh-like reticules; intermixed punctures very fine and inconspicuous on face, larger but shallow laterally and ventrally. Eyes small compared to other castes (EI 27–29, vs. 28–31 in major workers and 35–37 in gynes), flat, positioned dorsolaterally. Ocelli lacking, in some larger specimens position of median ocellus indicated by shallow impression. Frons with very fine impressed midline; frontal carinae slightly converging anteriorly, not elevated. Median carina of clypeus not reaching anterior clypeal margin, especially in small specimens. Mandibles mostly smooth, with rather dense punctures; masticatory margin with five teeth. Maxillary palpi long (PSI 28–35). Antennal scape long, its length roughly equal to head width (SI 87–104), moderately flattened, slightly widened towards apex, integument punctate. Antenna 12-segmented; antennal segment III approx. 1/5 shorter than each IV and V, and approx. 2/5 shorter than II. Mesosoma slender, moderately low. Microreticulation isodiametric or slightly transverse, dorsally denser than laterally. Metanotal region delimited from mesonotum by a shallow groove; groove delimiting metanotum from propodeum indistinct or missing. Dorsal and posterior outline of propodeum rounded in lateral view, or meeting at an obtuse angle, dorsal face slightly convex, posterior face flat to shallowly concave. Legs slender. Petiole with isodiametric reticulation; petiolar node moderately high, its short, slightly convex anterior and its rather straight posterior face forming a triangular shape in lateral view, its apex not truncated, rather rounded; node narrow in dorsal view, a crest indistinct; a medial depression indicated in most specimens. Gaster: dorsum of tergites I–III with extremely fine, dense, transverse microreticulation, slightly shiny; mesh-like reticulation wider on lateral areas of tergites I–III, tergite IV, and sternites , therefore meshes appearing not so strongly transverse, and the integument shinier. Exposed parts of tergite V and sternite V with dense, almost isodiametric reticulation, dull; base of tergite V (usually covered by tergite IV) sculptured as tergite IV. Colour: Body mainly reddish brown. Vertex of head, margins of clypeus, masticatory and lateral margins of mandibles, dorsum and ventral margins of mesosoma, mid portion of gastral tergites I–III, and legs slightly darker brown in most specimens; some specimens with darker area extending medially from head vertex to frons. Gastral tergites and sternites with very narrow hyaline margins. All gastral sternites, lateral fourths and posterior margins of tergites I–III, as well as entire tergites IV and V black. Pilosity: Dorsum of head with very short, inconspicuous, appressed and subdecumbent setae; a few very long, standing setae on frons near declivity to vertex, medial of frontal carinae, and on lateral portions of clypeus. Mesosoma and petiole with fine and short, whitish, velvety pilosity; long, standing, slightly undulated setae restricted to pronotum; declivity of propodeum and node of petiole with few very short standing setae. Gastral tergites with moderately dense, short whitish, decumbent setae and few slightly darker, longer standing setae, most of them in transverse rows near hind margins. Longest setae in transverse rows near hind margins of sternites and at base of gastral tergite V.

Notes: Minor workers of Colobopsis explodens show a continuous size variation across a remarkably wide range.

Phragmotic major: paratype major (n = 8): TL 7.30–8.71; HW 1.72–1.89; HL 2.25–2.58; HS 1.99–2.20; PS5 0.15–0.17 (6); PS6 0.15–0.17 (6); EL 0.50–0.56; SL 1.15–1.26; SW 0.17–0.20; ML 2.22–2.74; HaL 0.11–0.20; PH 0.59–0.69 (6); PL 0.45–0.51 (6); NH 0.40–0.45 (6); FeL 1.50–1.70. Indices: CI 71–77; SI 64–69; SWI 14–17; EI 28–31; PI 125–143 (6); FeI 87–95; PSI 14–17 (6).

Structures: Integument mostly dull, only head and legs shiny. Head large, subcylindrical, anteriorly truncated. On posterior areas of face punctation slightly stronger than in minor worker. Eyes somewhat larger and more distant from vertex compared to minor worker. Ocelli lacking, their positions often indicated by shallow grooves. Anterior part of head forming a large shield formed by clypeal and genal components, limited by a sharp and elevated crest so that the shield surface appears concave in lateral view. Shield with fine isodiametric reticulation and rather variable, mostly longitudinal rugae; most prominent are a pair of rugae along sides of clypeus and a single median carina that does not reach the anterior margin, often reduced towards base. Genal part with curved rugae of variable number, length, and distinctiveness, but only exceptionally reaching onto the anteromedial triangle. Additional longitudinal rugae on clypeus often present, including a usually distinct pair of paramedian rugae running from base of clypeus over the crest anteriorly towards middle of shield; in specimens with short median carina, the area between these carinae more or less grooved. Longitudinal striation more regular and pronounced on frons and genae up to level of antennal insertions, laterally on genae similarly long and strong. Mandible with sharp and high ventrolateral ridge, coarsely punctate, its lateral face weakly rugose-striate; masticatory margin with acute apex and few (1–3) more or less distinct, very blunt teeth in distal half. Maxillary palpi very short (PSI 14–16). Antenna considerably shorter than head width (SI 64–69) and stouter than in all other morphs; antennal scape distinctly widened towards apex. Mesosoma stouter and higher than in minors, especially promesonotum expanded; in lateral view dorsal and posterior face of propodeum forming an obtuse angle, somewhat less rounded than in minor workers, dorsally without concavity. Legs much shorter and stouter than in minors. Shape of petiole similar to minor workers, somewhat wider in dorsal view. Structures of gaster similar as in minor worker. Colour: Overall slightly darker than minor worker; head, legs and mesosoma reddish brown; gaster slightly darker chocolate-brown, becoming darker towards caudal apex, hyaline margins yellowish; elevated crest of frontal shield, anterior clypeal margin, frontal carinae, and masticatory and lateral margin of mandibles blackish brown. Pilosity: As in minor worker, except long setae on clypeus sides restricted to the area behind clypeal shield; mesonotum with standing setae which are approx. half the length of those on pronotum. Notes: The head shield with a sharp, elevated crest is typical for majors of the Colobopsis saundersi complex.

Queen
Paratype (n = 16): TL 10.50–12.16; HW 1.74–1.83; HL 2.28–2.45; HS 2.02–2.14; PS5 0.19–0.21 (13); PS6 0.19–0.23 (13); EL 0.62–0.66; SL 1.33–1.45; SW 0.20–0.22; ML 4.11–4.63; HaL 0.14–0.29 (15); PH 0.77–0.92 (11); PL 0.54–0.67 (10); NH 0.40–0.54 (11); FeL 2.25–2.35; OcW 0.13–0.16; OED 0.34–0.38; OcD 0.54–0.64; FWL 9.72–10.50 (11); MSW 1.68–2.15; 2r 0.50–0.64 (12); 4Rs+M 0.14–0.32 (12). Indices: CI 73–77; SI 75–80; SWI 15–16; EI 35–37; PI 123–150 (8); FeI 125–132; PSI 18–20 (13); OI 54–69; WVI 26–58 (12).

Structures: Head large, subcylindrical, anteriorly truncated, similar to that in major worker with the following exceptions: eyes larger than in workers (EI 35–37) and breaking outline of head in full-face view. Ocelli fully developed, their colour ranging from almost clear to reddish amber. Head shield sharply delimited, but slightly smaller than in major worker, distinctly narrower than head width. Striation of clypeus, frons, and genae similar as in major, though somewhat more strongly developed on lateral parts of shield. Mandible with sharp ventrolateral ridge; its lateral face weakly rugose-striate, narrower than in major; dorsal-anterior face punctured; masticatory margin with acute apex and 3–4 blunt teeth in distal half, mandible basally with blunt ridges. Maxillary palpi moderately long (PSI 18–20). Antennal scape moderately long, slightly shorter than head width (SI 75–80), somewhat widened towards apex.

Mesosoma large, structures as typical for caste; propodeum large and evenly convex in lateral view. Cuticular microstructures dorsally consisting of very fine punctation, with intermixed larger punctures, laterally finely reticulated. Legs stout, but not as short as in major. Forewing venation strongly reduced, as in most Camponotini; M-Cu absent; Mf2+ interstitial. Petiole distinctly wider than in workers; node more rounded in lateral view, in some specimens its apex shallowly impressed medially, in others with two shallow lateral impressions forming a trilobed outline. Gastral tergites I–IV and sternites I–IV with extremely fine and dense microstructures consisting of strongly transverse meshes; only sides of tergites with wide mesh-like reticulation and shiny; tergite V with dense isodiametric reticulation. Colour: Chiefly as in major worker. Head and pronotum reddish brown; ventral and posterior mesosoma, petiole, legs and gaster somewhat darker chocolate-brown; mandibles and ridges of clypeal shield blackish brown. Pronotum and mesonotum with very narrow yellow margins. Gastral tergites medially with very narrow hyaline margins; sternites with relatively broad posterior margins. Wings hyaline, but forewing cells along veins, as well as pterostigma darkened to brownish. On hind wing all veins pale yellow. Pilosity: Short pilosity and distribution of long setae on head, petiole, and gaster similar as in major worker, but that of mesosoma different; pronotum with few long, undulated setae. Medial part of mesonotum (between parapsidal furrows) with numerous long erect setae, scutellum with few long erect setae; lateral part of mesonotum in front of tegulae without setae. Notes: The head shield with a sharp, elevated crest is typical for gynes of the Colobopsis saundersi complex.

Male
This is the first detailed description and illustration of males from the Colobopsis cylindrica group.

Allotype: TL 7.11; HW 1.26; HL 1.20; HS 1.23; PS5 0.20; PS6 0.15; EL 0.44; SL 0.84; SW 0.11; ML 2.54; HaL n.a.; PH 0.46; PL.40; NH 0.29; FeL 1.83; OcW 0.18; OED 0.27; OcD 0.43; FWL 6.33; MSW 1.37; 2r 0.38; 4Rs+M 0.27. Indices: CI 105; SI 66; SWI 13; EI 35; PI 116; FeI 145; PSI 28; OI 62; WVI 70.

Paratypes (n = 5): TL 6.46–6.85; HW 1.24–1.29 (4); HL 1.14–1.24; HS 1.20–1.27; PS5 0.17–0.21 (4); PS6 0.13–0.17 (4); EL 0.43–0.46; SL 0.80–0.85; SW 0.10–0.12; ML 2.38–2.87; HaL n.a.; PH 0.45–0.49 (4); PL 0.38– 0.40 (4); NH 0.26–0.33 (4); FeL 1.71–1.86; OcW 0.18–0.19; OED 0.25–0.27; OcD 0.43–0.46; FWL 5.87–6.33; MSW 1.17–1.50; 2r 0.38–0.47; 4Rs+M 0.14–0.22. Indices: CI 104–110 (4); SI 64–67 (4); SWI 12–15; EI 35–36 (4); PI 113–123 (4); FeI 136–151 (4); PSI 27–30 (4); OI 53–62; WVI 31–53.

Head small, subtrapezoidal, eyes very large, round and protruding, EL more than one third of HL (EI 35–36). Ocelli very large, diameters larger than in gynes. Integument of head rather matt. Frons and genae finely reticulated, genae additionally finely punctured. Clypeus with some stronger punctures at margins (at base of setae), median carina weakly developed, present in proximal third of clypeus or entirely obsolete. Frons with impressed midline from median ocellus to level of antennal insertions. Frontal carinae weakly developed, converging more strongly than in minor worker. Mandible short with reduced dentition, masticatory margin with 2–3 blunt teeth; dorsal surface finely punctate. Maxillary palpi long (PSI 27–30). Antenna 13-segmented; scapes short (SI 64–67) and relatively slender. First funicular segment conspicuously enlarged distally, pear-shaped, 30–50% wider and ca. 20% longer than the following segment; all other funicular segments cylindrical, without modifications. Mesosoma large, structures as typical for alate ants. Mesoscutum anteriorly strongly convex with narrow impressed midline in posterior tenth. Scutellum moderately elevated; propodeum evenly convex. Cuticular microstructures of mesosoma consisting of a very fine reticulation with intermixed minute punctures at bases of short hairs, additionally with larger punctures dorsally at bases of erect setae. Legs very long and slender (FeI 136–151). Forewing venation strongly reduced, as in most Camponotini. M-Cu absent; 4Rs+M shortly developed or (more rarely) Mf2+ interstitial. Petiole small; in lateral view node more bluntly rounded than in female castes, anterior and posterior faces straight, not convex, apex not impressed medially in dorsal view. Gastral tergites I–IV and sternites I–IV with fine and dense microreticulation consisting of moderately transverse meshes; only sides of tergites with wide meshes and shiny; tergite V with almost isodiametric reticulation. Sternite VI posteriorly emarginated, sternite VII truncated.

Genital structures: Genital capsule approx. as long as wide in dorsal aspect, ventrally longer than dorsally, protruding from apex of gaster. Gonopod high, distally broadly rounded. Gonostylus elongated and acuminated, with reticulated microstructure (only visible at very high magnification) and some long setae. Basivolsella dorsally with roundish structure, ventrally with evenly distributed, comparatively short setae. Digitus large, evenly widened towards apex; apex rounded but with rectangular corner ventrally. Penis valvae in dorsal aspect broad at base, but very narrow distally. Valviceps leaf-shaped in lateral view, apically rounded; surface smooth; ventral margin with very fine serration. Colour: Mainly dark chocolate-brown. Head somewhat darker; eyes pale grey to blackish; ocelli translucent, ranging from almost clear to reddish amber. Antennae and legs lighter brown, fading into yellowish towards apices. Margins of mesoscutum, scutellum, and metanotum lighter yellowish brown. Gastral tergites medially with very narrow hyaline margins; sternites with relatively broad, indistinctly separated posterior margins. Wings almost hyaline, with a slight whitish tinge, but forewing cells along veins, as well as pterostigma darkened to brownish, all veins pale yellowish brown. On hind wing all veins pale yellow. Pilosity: On head setae sparsely distributed, short, inconspicuous, appressed, subdecumbent; a few very long standing setae on frons near vertex, and on anterior and posterior clypeal margins. Mandibles with dense short pilosity on lateral face, and few moderately long setae on anterolateral margin. Short pilosity and distribution of long setae on mesosoma, petiole, and gaster similar as in gyne, but pronotum lacking long, undulated setae. Medial part of mesonotum (between parapsidal furrows) with numerous long erect setae, scutellum with few long erect setae; lateral part of mesonotum in front of tegulae without setae. Tegulae with dense brush of setae. Petiole with a few stout setae anteroventrally. Petiolar node lacking any standing setae; gastral tergite I without or with few subdecumbent, moderately long setae. Posterior gastral tergites and sternites (segments II and following) with sparse, relatively long, obliquely standing setae.

Type Material
Paratypes: 59 minor workers, 8 major workers, 16 gynes, and 6 males dry mounted; > 500 imagines stored in 96 % ethanol (housed in Universiti Brunei Darussalam, the Natural History Museum Vienna, the University of California (Davis, USA), the Natural History Museum of Los Angeles County (Los Angeles, USA), the Thailand Natural History Museum (Technopolis, Thailand), and the collection of H. Zettel (Vienna, Austria)).
 * 19 minor workers, 2 major workers, 12 alate gynes, 4 dealate gynes, 6 males (including allotype) (all dry mounted), as well as 8 males, 2 alate gynes, ca. 500 minor workers (in alcohol) from the same nest sample as holotype
 * 1 major worker, same locality and collector as holotype, 17.IV.2015, “YG 373 main natural nest”
 * 1 major worker, same data as holotype (“YG doorkeeper #19”)
 * 2 major workers, same data as holotype except 20.IV.2015, leg. A. Kopchinskiy (“cf. YG 39 (351) artificial nest”)
 * 8 minor workers, 2 major workers, same locality as holotype, 2002, leg. D.W. Davidson (“YG KB02-108”)
 * 4 minor workers, same locality and collector as previous, no collection date, “YG 2025”
 * 5 minor workers, same locality and collector as previous, I.2012, “YG T-trail (202)”
 * 5 minor workers, same locality and collector as previous, 15.V.2014, “YG-2 (73)”
 * 7 minor workers, same locality and collector as previous, 15.V.2014, “YG-2 (49)”
 * 2 minor workers, same data as previous except Batu Apoi Forest Reserve, N04°32', E115°10', 200 m a.s.l., 25.XI.2004, (“CAYG A-370”)
 * 15 minor workers (on 5 pins), same data as previous, except N04°55', E115°19', 60 m, 3.VII.2002, (“YG KB02-108 voucher”)
 * 4 minor workers, Thailand, Chumphon Province, Krom Luang Chumphon W.S, 3.II.2002, leg. W. Jaitrong (“WJT02-TH-0116”)
 * 5 minor workers, West Malaysia, Kelantan, 60 km NE Tanah Rata, Tanah Kerajaan, 1000 m a.s.l., 12.–30.IV2007, leg. P. Cechovský.

Etymology
Present participle of Latin explodere, referring to the “exploding”-like autothysis behaviour.