Neomachilellus (Neomachilellus) mercurialis Palacios-Martinez 2024, sp. nov.
Creators: name: Palacios-Martinez, Iñigo
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Archaeognatha
Meinertellidae
Neomachilellus
Neomachilellus mercurialis

description: Neomachilellus (Neomachilellus) mercurialis sp. nov. Palacios-Martinez
Material examined. Holotype, MUBI-ENTO-PA.TIPO:07. Adult female, one broken antenna, incomplete cerci, “tierra firme” forest of Los Amigos Biological Station (LABS), on trail 9, past the crossing with trail 22, on the trunk of a tree (12°32’54.9 “S 70°06’17.0 “W; 291 m elev.), 5 April 2023, Palacios-Martínez, I. leg. Paratypes, MUBI-ENTO-PA.TIPO:08. Adult female, tail and cerci deteriorated, same sampling point as holotype, 6 April 2023, Palacios-Martínez, I. & Castro, R. leg.; MUBI-ENTO-PA. TIPO:09. Adult female, decayed and dissected, “tierra firme” forest of LABS, crossing between trails 19 and 27 (12°34’01.6 “S 70°05’30.8 “W; 269 m elev.), 5 April 2023, Ávila, A. leg (Fig. 2).
Diagnosis. Ocelli submedian, widened, oval-shaped. Pigmentation present on articles I‒VII of the maxillary palpi. Strong pigment on the femora, tibiae, and tarsi, femora and tibiae lacking spines or prominent spiniform setae. Tarsi with spine-like setae and lacking pulvillus characteristic of the nominal subgenus.
Description. Body length 8.96‒9.37 mm (n=3), width 1.6‒1.9 mm. Antennal length 6.6‒6.9 mm, cerci broken near apex, 6.6‒6.7 mm long. Single compound eye width 0.77‒0.82 mm, and length 0.67‒0.7 mm. Single paired ocellus width 0.68‒0.7 mm. Ovipositor length 2.29‒2.32 mm. Head, cephalic appendages and legs lacking scales (Fig. 3). Coxal styli absent.
General body coloration whitish to yellowish or bright brownish, with hypodermal pigment. Antennal bases, occiput, frons, gena, lateral sides of clypeus, labrum, labium, maxillae, mandibles, maxillary and labial palpi, antennae, legs, thorax, abdominal tergites and sternites with brownish-blackish hypodermal pigment of varying intensity. Body scale colors ranging from brown or grey to dark brown (Figs. 2C, 3). Head (Fig. 4C) with 1+1 dark spots between the ocelli; strong yellowish pigmentation surrounding the ocelli, compound eyes, and spots below the compound eyes. Dark or brownish spots present at the insertion of the antennae. Antennae shorter than body, ratio of scape length:width approximately 2.13:1 (Figs. 4B, D). Distal flagellomeres divided into 4 annuli. Antennal flagellum with light yellowish-brownish pigmentation, evenly distributed. Each annulus of the flagellomeres with a ring of sensitive hairs (Figs. 4B, D). Ratio of antennal length to body length approximately 0.74. Clypeus and labrum covered with numerous short simple chaetae, with the front half of the clypeus adorned with numerous small, dark chaetae. Cerci approximately 0.71‒0.74 times as long as body length, each terminating with one large lateral spike. In life, cerci with white rings, fading in alcohol (Figs. 2C, 3).
Compound eyes light grey with brown and yellow speckles when viewed in ethanol. Length:width ratio of each compound eye approximately 0.7‒0.75, ratio of the contact line length to eye length about 0.53. Paired ocelli oval and submedian, appearing blackish and reddish, color darkened by alcohol. Ratio of ocellar width to compound eye width about 0.69, ratio of the length of the interocellar distance to the width of the ocelli approximately 0.9 (Fig. 4C).
Maxillary palpus with pigmentation on all segments, characterized by light yellowish pigment with distinct dark patches following a specific pattern (Figs. 5A, B): Article I with light pigmentation, mainly concentrated in its proximal area; the second article displays strong pigmentation from the proximal area to the base of the segment in the distal area; the third article exhibits strong pigmentation covering about 2/3 of the segment, with an additional patch at its distal zone; the fourth article with two patches of strong pigmentation, located at the distal zone to about the first third of the segment, and the base of the proximal zone; on the fifth article, two patches of strong pigment, one covering the distal area uniformly, while the other extending discontinuously from the proximal to almost the medial area; the sixth article with a strong pigmentation in its proximal region, gradually lightening towards the distal area on its dorsal side; and article VII with light pigmentation primarily on dorsum. Hyaline spines present on dorsal side of the maxillary palpus, distributed as follows: segment V: 3‒4; VI: 13‒16; VII: 22‒25. Last article longer than the sixth, with ratios of maxillary palpus articles with respect to the preceding one (n/(n-1)) as follows: III = 0.89‒0.95; IV = 0.97‒1.03; V = 1.45‒1.48; VI = 0.81‒0.86; VII = 1.02‒1.05. Terminal spine of article VII longer than the previous ones, with shorter spines in the basal area of the article. Dark thin sensitive setae present on the dorsal side of articles V to VII and on both dorsal and ventral sides of articles I to IV. A cluster of thick dark setae on the distal ventral side of article III (Figures 5A, B).
Apical article of the labial palpus similar to that of maxillary palpus (Fig. 4A), with a length-to-width ratio 0.97. Article II of the labial palpi ovoid, covered with sensitive setae. The distal half of the dorsal surface of the III article of the labial palpi with shorter sensory sensilla. Overall pigmentation whitish, with several dark stripes in the medial zone of the second article, in the inner side of the III article, and on the ventral distal surface article I.
Ratios of lengths to widths of femora, tibiae, and tarsi provided in Table 2. The ventral surface of coxae, trochanters, femora, tibiae, and tarsi largely devoid of spines, femora with sparse spine-like setae on their ventral surface. Tarsi with spine-like setae and long setae on their ventral surface. Long sensory hairs abundant on legs, particularly on the dorsal surface. Fore femur with prominent dorsal bulge proximally, adorned with robust sensory hairs.
On foreleg (Figs. 6A, B) trochanter with weak pigmentation on inner face, extending proximally-distally; femur with strong pigmentation patch on its inner side, darkening from the medial to the distal side, and robust patch on the dorsal outer side; tibia with two distinct dorsal patches and a large patch laterally extending from most of length; tarsus with strong pigmentation proximally and fainter pigmentation distally, middle region pale.
On middle leg (Figs. 6C, D) pigmentation on trochanter and coxa faint; femur with patch of strong distal pigmentation on internal side, attenuating toward the medial area; tibia with strong pigmentation up to half its width in the inferior zone, with a patch of strong pigmentation proximally and weaker pigmentation distally; tarsus pigmented proximally and distally, pale in middle.
Hind leg (Figs. 6E, F) with pigmentation in the basal-proximal part of the coxa; femur with band of light pigment laterally and ventrally; tibia with strong pigmentation from the proximal to the medial area; tarsus pigmented proximally and distally, middle region pale.
Abdominal segments II–VII with 1 + 1 eversible vesicles. Coxosternites bright yellowish or without color. Urocoxites lacking spines, sternites small, triangular. Ratios of lengths of the urosternite, stylus (without apical spine), and urocoxites I–IX presented in Table 3.
The ovipositor of the quaternary type (Sturm & Bach de Roca 1993), characterized by slender, elongate structure, reaching or extending beyond the apex of styli IX. Gonapophyses with 64‒68 divisions, apical divisions in each gonapophysis with a terminal spine as long as the three most distal divisions. Apical divisions of the anterior gonapophyses with 3‒4 thin chaetae in addition to sensory setae and apical spines, and several minute sensory conules. Posterior gonapophyses with approximately 28 distal divisions with one macrochaeta on each 1 or 2 divisions and a pair of thin setae per division, subsequent divisions glabrous (from about the 30th division from the distal apex to the basal part).
Habitat and habits: The specimens used for describing this species were discovered on tree trunks with varying degrees of bark coverage, ranging from fully intact to partially peeled. These trunks typically had a diameter ranging from 55 to 115 cm. The specimens were found camouflaged among the lichens that covered these trunks within the rainforest of LABS, particularly in areas with over 75% canopy cover (see Figs. 2A). Encounters with the specimens occurred between 17:30 and 20:00, with the exception of one specimen collected at 16:15 on a rainy day, probably due to the reduced amount of available light. Two specimens were found at a height no more than 0.7‒0.9 cm above the ground on a hot and humid day, without rain. Another specimen was located at 2.2-m height on a similar tree during rainfall. It was noted that the specimen positioned lower on the trunks would drop to the ground as a defensive mechanism. This behaviour may suggest a life cycle alternating between ground level during hot, dry days, and upper trunk areas during rainy days to seek shelter from ground flooding. Observations indicated that the species exhibits nocturnal habits, becoming active from 17:30 onwards.
Etymology. The specific epithet stems from the illicit artisanal gold mining and its rampant mercury usage in extraction, an ongoing and significant issue across the Madre de Dios river basin in southeastern Peru (Gerson et al. 2022). Furthermore, “saltadora arborícola del mercurio” in Spanish and “tree mercurial jumping bristletail” in English are suggested as vernacular names for this newly discovered species.
Differential comparison. The new species has been described through the observation and morphological measurements of three female individuals. The great size of the last segment of the maxillary palpus with respect to the previous one (n/(n-1)>0.9) places Neomachilellus mercurialis sp. nov. in a group composed of eight extant species: N. adisi, N. geayi, N. lamtoensis, N. nimbensis, N. muticus, N. peruvianus, N. rangeli and N. scandens. The size of the antennae, shorter than the body, separates this species from the remaining of this muticus-group of species. The position and affiliation of the two African species (N. lamtoensis and N. nimbensis) within Neomachilellus may be questioned because they do not seem to follow the same neotropical biogeographical pattern as the rest of the species within the genus. Furthermore, the new species differs from these two in the lack of strong pigmentation of the coxae. Among the remaining species in this group, five are endemic to the Amazon rainforest (N. adisi; N. geayi; N. peruvianus; N. rangeli; and N. scandens) and one to Clipperton Island and the Galapagos archipelago (N. muticus). Within this group, the new species differs from the others in the following features: 1) The ovipositor of N. peruvianus does not extend beyond the terminal spine of stylet IX, while that of N. mercurialis sp. nov. does, as it differs on the length of the last maxillary palpus article with respect to the previous one (1.13‒1.27), the lack of pigmentation on article VI of the maxillary palpus, and the scarce pigmentation on its legs. 2) The lack of pigmentation in the article VI of the maxillary palpus, the number of divisions of the gonapophyses (54‒57), the annulation of the antennal chain (9‒17), and the antennae longer than the body, differentiate N. muticus sensu Paclt 1976 from the new species. 3) The number of gonapophysis divisions (55‒60), the different intensity and wide extent of pigment on the tibiae, especially on the forelegs (Wygodzinsky 1978), and the gonapophyses segmentation (55‒60), separate N. scandens from the new species. 4) The short interocellar distance and the relative proportions of the ocelli and compound eyes (Wygodzinsky 1978), and the gonapophysis segmentation (68‒75), separate N. adisi from N. mercurialis sp. nov. 5) The legs and compound eye proportions, trochanter pigmentation in N. geayi (Mendes 1996) and the relation of the length of the last segment with respect to the previous one (1.3) set it apart from the new species. 6) The spiniform setae on the dilated area of the distal outer surface of the foreleg coxae, the differing distribution of pigment on the palpi and legs and the gonapophysis segmentation (59‒60) separate N. rangeli from the new species.
description: Published as part of Palacios-Martinez, Iñigo, 2024, New species of Neomachilellus Wygodzinsky 1953 (Insecta: Archaeognatha: Meinertellidae) from Madre de Dios, Peru, pp. 417-429 in Zootaxa 5448 (3) on pages 420-426, DOI: 10.11646/zootaxa.5448.3.5, http://zenodo.org/record/11231985