Contributions to the Taxonomy of Arlesminthurus Bretfeld and Calvatomina Yosii (Collembola, Symphypleona, Appendiciphora), with the Description of New Species from Northeastern Brazil †

Simple Summary Springtails (Hexapoda, Collembola) are tiny insect-like animals found mostly in soil habitats. Symphypleona is one of the four orders of springtails, gathering species with rounded bodies and antennae longer than the head. Here, we describe in detail two new species of Neotropical Collembola, both from northeastern Brazil: Arlesminthurus caatinguensis sp. nov. and Calvatomina gladiata sp. nov. We also provide detailed notes on their morphology, especially on their chaetotaxy (the shape and arrangement of the chaetae over the head, body and appendages), to give support to future studies on comparative anatomy, taxonomy and evolution of the Symphypleona. Abstract Arlesminthurus Bretfeld is a small genus of Neotropical Bourletiellidae, with only four described species so far. Calvatomina Yosii is a widespread taxon of Dicyrtomidae, with most species known from the tropics. Here, we describe two new species from northeastern Brazil: Arlesminthurus caatinguensis sp. nov. and Calvatomina gladiata sp. nov. We also provide a detailed chaetotaxic study for Arlesminthurus for the first time, with updated diagnoses and identification keys for the Neotropical species of both genera and notes on their morphology. Arlesminthurus caatinguensis sp. nov. resembles A. aueti Arlé in body color pattern, male head and dental chaetotaxy. The discovery of one bothriotrichum-like sens on the large abdomen of the new species needs to be investigated as a possible generic diagnostic feature, but we suggest that this structure is homologous to the S-sens seen in at least four Bourletiellinae genera, and they are likely related to each other. Calvatomina gladiata sp. nov. belongs to the rufescens-group and resembles C. rufescens Reuter and C. guyanensis Nayrolles and Betsch in some aspects of the head, dental and abdominal chaetotaxy. These descriptions represent the first record of Arlesminthurus from Caatinga and the first nominal species of Calvatomina from Brazil.


Introduction
Symphypleona Börner (sensu Bretfeld [1]) is an order of springtails with global distribution and holding almost 1300 species in 122 genera and 10 families [2]. Of these, about 1100 species in 109 genera and eight families belong to the Appendiciphora [3], a group which is recognized by the presence of a pair of subanal appendages on the female's small abdomen [2,4].
In Brazil, 71 nominal species of Symphypleona have been recorded so far, of which 46 species in 18 genera and seven families represent the Appendiciphora [5]. Of these families in the country, Bourletiellidae is represented by only eight species in five genera and Dicyrtomidae by three species in one single genus [5]. Very little is known about these families, considering that they are among the most diverse and widespread Symphypleona, just after the Sminthuridae [2], and the fact that Brazil shelters several species-rich habitats.
An example of this lack of knowledge is seen in northeastern Brazil, where only 16 species of Symphypleona have been registered until now, two of Bourletiellidae and only one of Dicyrtomidae [5][6][7], but none of the genera Arlesminthurus Bretfeld, 1999 [4] (Bourletiellidae) or Calvatomina Yosii, 1966 [8] (Dicyrtomidae), although the latter has been recorded with non-nominal specimens in different regions from Brazil [7,9,10].
Arlesminthurus is a bourletiellid genus that is exclusively Neotropical, currently with four described species, three from Brazil and one from Nicaragua. Such species are usually associated with aquatic environments [5,[11][12][13][14]. On the other hand, Calvatomina is the largest genus of Dicyrtominae, and it is widely distributed and holds 34 valid species, most of them from tropical areas, but with only five taxa recorded from the Neotropical region [2,[15][16][17][18]. Although the genus may be widespread in Brazil, as already stated, there has been no nominal species of it recorded from the country until now. All known species of Brazilian dicyrtomids belong to Ptenothrix Börner, 1906 [2,5,19].
Herein, two new species, Arlesminthurus caatinguensis sp. nov. and Calvatomina gladiata sp. nov., are described from northeastern Brazil and illustrated in detail. For the new species of Arlesminthurus we provide a detailed map of the chaetotaxic homologies, the first one for the entire genus (for Calvatomina a similar chaetotaxic study was presented in Nayrolles and Betsch [18]). We also provide updated diagnoses to both genera, a key to all species of Arlesminthurus and another to the Neotropical taxa of Calvatomina, as well as comparative tables plus notes on the morphology of each genus.

Materials and Methods
Specimens preserved in ethanol (92% or 70%) were cleared in Nesbitt's solution and then mounted on glass slides in Hoyer's medium following the procedures described in Cipola et al. [14]. Maps of species localities were made after Shorthouse [20].
The type material was deposited at the Invertebrate Collection of the National Institute of Amazonian Research (INPA), Manaus, and at the Collembola Collection of Biosciences Center of Federal University of Rio Grande do Norte (CC/UFRN), Natal, Brazil.

Arlesminthurus caatinguensis sp. nov. Cipola, Lycarião and Medeiros
Description: Total length (head + large abdomen) of holotype 0.96 mm, in males 0.88-0.96 mm (n = 3), and females 1.12-1.13 (n = 3). Body with different types of chaetae as presented in Figure 3. Both sexes with the same color pattern. Frontal head with one longitudinal reddish strip from the anterior to the postocellar region, with a depigmented interruption in the subantennal region; body with dark bluish to greenish pigments on antennae, head (except clypeal part to postocellar and ventro-distal region) and on large and small abdomens (except ventrally). Large abdomen with depigmented patches and strips in specific patterns, such as a longitudinal line from the head to one third of the large abdomen, a circle followed by two transverse bands, and distally 5-6 small circles; laterally with about 10 depigmented circles (seven median and three distally). Legs with traces of pigments, mainly in the joints between the segments; eyepatches black ( Figure 4).
Diagnosis: Both sexes with the same color pattern, with head with a longitudinal strip, large abdomen anteriorly with two lateral spots and one longitudinal strip depigmented; Ant IV with eight subsegments, Ant III with two oval organ-like microsensilla on males and only one ventral in females, Aai chaeta absent; male's head with 0-4 spines and 5-9 spine-like chaetae on the interocular region, frontal region with γ inferior chaeta short and robust and γ superior chaeta apically hooked, f line with the unpaired chaeta, if  present, subequal to the others; male's thoracic region with 1-4 spines and 2-3 spine-like  chaetae, abdominal region with 13-15 spines and 13-16 spine-like chaetae; large abdomen inferiorly with one bothriotrichum-like sens; female's small abdomen with one robust spine-like chaeta on the superior lobe; unguis inner tooth present; dens with eight  chaetae on each side, with the exception of the ventral formula with 3,3,1,1…1 chaetae, outer side with eight chaetae somehow elongated, inner side with seven elongated chaetae; mucro wide and with two invaginations on both sides (inner and outer).
Description: Total length (head + large abdomen) of holotype 0.96 mm, in males 0.88-0.96 mm (n = 3), and females 1.12-1.13 (n = 3). Body with different types of chaetae as presented in Figure 3. Both sexes with the same color pattern. Frontal head with one longitudinal reddish strip from the anterior to the postocellar region, with a depigmented interruption in the subantennal region; body with dark bluish to greenish pigments on antennae, head (except clypeal part to postocellar and ventro-distal region) and on large and small abdomens (except ventrally). Large abdomen with depigmented patches and strips in specific patterns, such as a longitudinal line from the head to one third of the large abdomen, a circle followed by two transverse bands, and distally 5-6 small circles; laterally with about 10 depigmented circles (seven median and three distally). Legs with traces of pigments, mainly in the joints between the segments; eyepatches black ( Figure  4).    Figure 7A); A subsegment with a unilobed apical bulb (AI), one dorso-lateral microsensillum (AII), and 13 dorsal and 10 ventral chaetae, AI-III areas with eight, eight and nine chaetae, respectively (Figure 7A-C); M subsegment subdivided into six (M1-6), each with a single whorl of generally 10 chaetae, two latero-distal chaetae smaller (Heae ventrally, Hppe dorsally), both present or absent on M3 and M4, and Heae present or absent on M6; B subsegment with 33-40 chaetae, 7 BA, 21-28 BM (3-4 whorls with seven chaetae each) and five BB (Gpi, Gi, Gai absent) ( Figure 7A,D-E). Ant III with 37 chaetae of different sizes, 23 dorsal and 14 ventral; distal whorl ventrally with two conical organs inside a single oval invagination, two oval organ-like microsensilla (one dorsal and one ventral, only one ventral in females), and six chaetae (Ai, Api, Ap, Ape, Ae, Aa), Ai slightly smaller, Ap smaller, and Api and Ape reduced; Aai absent, but possibly homologous to one of the ventral oval organ-like microsensilla ( Figure 7A,F-G). Ant II with 18 chaetae, two ventral and 16 dorsal; distal row with seven chaetae and one bothriotrichum-like sens ventrally; proximal row with three chaetae ( Figure 7A). Ant I with seven chaetae, six dorsal, one smaller, as well as one ventral chaeta ( Figure 7A). Head length of holotype as 0.027 mm, in males 0.026-0.027 mm, and females 0.032-0.034 mm. Eyes 8 + 8, A-B, E-F and H larger, D smaller, others subequal; two subequal interocular chaetae present ( Figures 5A, 8A and 9A). Labrum distally with two inner papillae and one W-shaped crest and four (a1-2), five (m0-2) and five (p0-2) chaetae, a2 and p0-1 smaller, p2 larger, others subequal; prelabral (pl) chaetotaxy with 3 + 3 subequal chaetae ( Figures 8A and 9A,B). Labium with one minute and five normal and smooth lpc ( Figure  8C). Labial palp with six main papillae (H, A-E), formula of guard appendages as: H(2),  Figure 7A,D,E). Ant III with 37 chaetae of different sizes, 23 dorsal and 14 ventral; distal whorl ventrally with two conical organs inside a single oval invagination, two oval organ-like microsensilla (one dorsal and one ventral, only one ventral in females), and six chaetae (Ai, Api, Ap, Ape, Ae, Aa), Ai slightly smaller, Ap smaller, and Api and Ape reduced; Aai absent, but possibly homologous to one of the ventral oval organ-like microsensilla (Figure 7A,F,G). Ant II with 18 chaetae, two ventral and 16 dorsal; distal row with seven chaetae and one bothriotrichumlike sens ventrally; proximal row with three chaetae ( Figure 7A). Ant I with seven chaetae, six dorsal, one smaller, as well as one ventral chaeta ( Figure 7A). Head length of holotype as 0.027 mm, in males 0.026-0.027 mm, and females 0.032-0.034 mm. Eyes 8 + 8, A-B, E-F and H larger, D smaller, others subequal; two subequal interocular chaetae present ( Figures 5A, 8A and 9A). Labrum distally with two inner papillae and one W-shaped crest and four (a1-2), five (m0-2) and five (p0-2) chaetae, a2 and p0-1 smaller, p2 larger, others subequal; prelabral (pl) chaetotaxy with 3 + 3 subequal chaetae ( Figures 8A and 9A,B). Labium with one minute and five normal and smooth lpc ( Figure 8C). Labial palp with six main papillae (H, A-E), formula of guard appendages as: H(2), A(0), B(4), C(0), D(5), E(5) + l.p. finger-shaped, smooth and not reaching the a.a. base ( Figure 8D). Mandibles typical, right with five and left with four incisive teeth, without any other modifications. Maxillae with three outer teeth and six lamellae, two larger in leaf-shape, two elongated and capitate, and two unequal and pin-shaped ( Figure 9C). Maxillary outer lobe with t.a. and b.c. subequal in length; sublobal plate (sl.p.) with one appendage and oral fold with two chaetae, all smooth ( Figure 9D). Basomedian and basolateral labial fields respectively with four and five chaetae, three slightly smaller and two larger, others subequal ( Figure 8E). Postlabial chaetotaxy with four transversal chaetae of a line ( Figure 8E).
Male's large abdomen ( Figures 5B and 10A,B): Th II with two m chaetae, Th III m and p with two and 6-7 chaetae, respectively, 1-4 as spines or spine-like chaetae. Abd I a, m and p with five, two and two chaetae (one spine in each line), respectively. Abd II a, m and p with 7-8, eight and nine chaetae, respectively; a and m with three spines and one spine-like chaeta, p with 3-4 spines and 1-2 spine-like chaetae, each line with ABC bothriotricha aligned transversally. Abd III a, m and p with eight, seven and six chaetae, respectively; a with three spine-like chaetae, m and p respectively with one and 0-1 spine, and one and 1-2 spine-like chaetae. Abd IV a, m and p with five, six and four chaetae, respectively; a with three and b and c with one spine-like chaetae, respectively, m with one small bothriotrichum-like sens on the inferior region. Posterior region dorsally with 2-3, three and two chaetae and one oval organ. Furcula basis with 15 chaetae with different sizes but with same homology in both sexes ( Figures 10 and 11).
Etymology: Refers to the Caatinga biome where the new species was found. Remarks: Arlesminthurus caatinguensis sp. nov. resembles A. salinensis (Arlé, 1971) [12] from the Pará state, Brazil, and A. aueti (Arlé, 1961) [11], of which the type locality is the "Tatuari" River, currently known as "Tuatuari" River, situated in the Indigenous Park of "Xingu", near Gaúcha do Norte municipalities, the Amazon Biome of the Mato Grosso State, Brazil. These species are similar based on the absence of sexual dimorphism in color patterns, the dens inner row with seven larger chaetae, and wide mucro with invaginations on the outer side (Table 1). However, A. caatinguensis sp. nov. is more similar to A. aueti based on the head with a median longitudinal strip, the large abdomen anteriorly with two lateral spots and one longitudinal strip depigmented, the male's head with interocular spines (absent in A. salinensis) and the γ inferior short and robust frontal chaeta (normal and hooked at the apex in A. salinensis) and the mucro with two invaginations on the outer side (four in A. salinensis). However, A. caatinguensis sp. nov. differs from A. aueti based on the Ant IV with eight subsegments (6-7 in A. aueti), the male's γ superior frontal chaeta, which is apically hooked, and the f line unpaired chaeta, which is subequal to the others (γ superior chaeta is swollen and f unpaired chaeta is larger in A. aueti), the unguis inner tooth (absent in A. aueti) and the mucro inner edge with two invaginations (irregular in A. aueti). In addition to these characteristics, the new species also differs based on the dens ventral formula with 3,3,1,1 . . . 1 chaeta, whereas in A. aueti it is apparently 1,3,1,1 . . . 1 (see Arlé [12], figure 24).
In A. salinensis the color pattern is diffuse on the head and the occipital region and the body is depigmented, whereas in A. caatinguensis sp. nov. there is a distinct color pattern, as previous described and illustrated in Figure 4. Arlesminthurus caatinguensis sp. nov. also differs from the first species based on the unguis inner tooth, which is present and well developed (vestigial in A. salinensis), and the mucro with two invaginations on the inner side (smooth in A. salinensis).          On the small abdomen of the female of A. caatinguensis sp. nov. there is a robust spine-like chaeta (?) between mps1 and mps2 chaetae ( Figures 6A and 13A,B,D), without a clear homology (following Betsch 1997 [31]), which has never been reported in any species of Arlesminthurus before [4,[11][12][13]. This feature may be an autapomorphy of the new species; however, it should be further investigated in other species of the genus, especially the Brazilian ones, which lack details on the small abdomen chaetotaxy. Other features like the head and large abdomen spines of males, the presence of an oval organ on the dorso-posterior region of the large abdomen and on the superior and inferior lobes of the small abdomen ( Figure 6A) may be shared, at least, among some of the Brazilian species and must be better studied in previously described taxa. Further comparisons among Arlesminthurus species are presented in Table 1.
With the description of the new species, we intend to provide a detailed map of chaetotaxic homologies and other morphological aspects of Arlesminthurus, to provide further foundations for future species descriptions and comparisons within the genus and among the Bourletiellidae.
Remarks on the Neotropical fauna: Calvatomina rufescens (Reuter, 1890) [40] is one of the most puzzling species of the genus. It was originally described by Reuter based on specimens collected from a greenhouse in Helsinki, Finland. Subsequently, it was redescribed by Hüther [41] after the analysis of its type material. Hüther also suggested that the species was introduced, as it shows many resemblances with other tropical taxa and it was only collected from greenhouses [4,16,41]. Calvatomina rufescens has been considered widespread, but most records outside of its type locality are doubtful due to incongruences in the chaetotaxy of the females' small abdomen [2,4]. However, this is not the case for the specimens from Colombia and Puerto Rico [16,17]. Although the drawings of Mari-Mutt do not represent chaeta as1(M) as blunt acanthoid, in his notes the author explains that M is polymorphic in the Colombian specimens, and it can be a regular pointed or a long blunt acanthoid chaeta, as well as as3(N'), which can be a thick or a regular pointed chaeta (Mari-Mutt [16] pp. 377-378, figures 64 and 65). The same polymorphism of the M chaeta was recorded to Puerto Rican specimens by Soto-Adames ( [17], pp. 64-65, figure 20). Considering such polymorphism, the only clear differences among Mari-Mutt, Soto-Adames and Hüther's drawings are the absence of the short regular chaetae mps'(G) and ami1(T) in the latter's representations, which could be easily overseen due to their positions. To endorse this point of view, Hüther also did not represent chaetae ps1-2, which are primary elements seen in most if not all Symphypleona [31]. Hüther's redescription of C. rufescens also matches the notes of Mari-Mutt in key features like color pattern, empodial complex morphology, chaetotaxy of the parafurcal area, collophore with one chaeta on each side, tenaculum with two chaetae, manubrium with 10 chaetae and dens ventral chaetae formula from the apex to the basis as 3,2,1,1,0,0,1, with the proximal chaeta smaller and far apart from the others. Because of this, at this time and with the current knowledge of the species morphology, we believe the records of Neotropical C. rufescens from Colombia and Puerto Rico are valid, since they fit the redescription provided by Hüther [41]. Even so, this conclusion does not exclude the possibility that C. rufescens could represent a species-complex, due to its widespread distribution and since further data not represented by the previous authors may have obscured closely related taxa.
Calvatomina rufescens var. discolor (Schött, 1902) [42] is a similar case to C. rufescens. This variation of the late species was described in Sweden based on material also collected from greenhouses [16,42]. Schött presented a short description lacking chaetotaxic data, but remarked that his specimens' color pattern was characteristic and distinct from that of C. rufescens described by Reuter [40]. Calvatomina rufescens var. discolor was not revised by Hüther, but it was considered by the author to be "of the same species" in a short note provided in his revision, which lacks any comparative data or further explanation (Hüther [41], pp. 50-51), and it was disregarded by important revisions like Bretfeld [4] and Fjellberg [43]. However, Mari-Mutt [16] proposed a new status to C. rufescens var. discolor as a full species based on material collected from Colombia. His specimens presented the same J-shaped band of purple-violet pigment laterally on the large abdomen described by Schött and were similar to the Colombian specimens of C. rufescens. Even so, a similar color pattern was also described to C. christianseni (Delamare-Debouteville and Massoud, 1964) [15] in Suriname (see Delamare-Debouteville and Massoud [15], p. 78, figure 40B) and is similar to C. nymphascopula Soto-Adames, 1988 [17] from Puerto Rico (see Soto-Adames [17], p. 66, figure 22). Since there are no further useful data on the morphology of C. discolor from Sweden, at this time we cannot confirm if the Colombian species matches the Swedish one, nor can we refute this hypothesis. We thus consider Calvatomina discolor as a species inquirenda, and its type material, if available, must be redescribed in order to clearly circumscribe its identity. Nevertheless, Mari-Mutt's description of C. discolor is detailed and represents a distinct Neotropical species, so we provisionally propose C. discolor sensu Mari-Mutt [16] to stand for it until further data on the material from the type locality are presented.  presented the same J-shaped band of purple-violet pigment laterally on the large abdomen described by Schött and were similar to the Colombian specimens of C. rufescens. Even so, a similar color pattern was also described to C. christianseni (Delamare-Debouteville and Massoud, 1964) [15] in Suriname (see Delamare-Debouteville and Massoud [15], p. 78, figure 40B) and is similar to C. nymphascopula Soto-Adames, 1988 [17] from Puerto Rico (see Soto-Adames [17], p. 66, figure 22). Since there are no further useful data on the morphology of C. discolor from Sweden, at this time we cannot confirm if the Colombian species matches the Swedish one, nor can we refute this hypothesis. We thus consider Calvatomina discolor as a species inquirenda, and its type material, if available, must be redescribed in order to clearly circumscribe its identity. Nevertheless, Mari-Mutt's description of C. discolor is detailed and represents a distinct Neotropical species, so we provisionally propose C. discolor sensu Mari-Mutt [16] to stand for it until further data on the material from the type locality are presented.  Diagnosis: Specimens mostly brownish, with a light sword image on dorso-anterior large abdomen ( Figure 19). Ant III with 10, Ant II with two cup sensilla, Ant I with seven regular subequal chaetae ( Figure 20A-C). Head clypeal area with 4-5 unpaired central chaetae and two, one, two, one cup sensilla on lines b, c, e and f, respectively, line f with one acanthoid chaeta laterally to antennal basis ( Figure 20D,E). Sublobal plate with one chaeta-like appendage ( Figure 20K). Labial papillae with five proximal chaetae ( Figure  20L). Epicoxae II-III with one acanthoid chaeta each; femurs II-III with one oval organ each, tibiotarsi I-III with four each; tibiotarsi I-III with five cup sensilla each ( Figure  21A-C). Collophore with two chaetae on each side, tenaculum with two chaetae on each side. Manubrium with nine dorsal chaetae on each side ( Figure 21G). Dens dorsally with 25 chaetae; dens ventral formula from apex to the basis as: 4,2,1,1,0,0,1 ( Figure 21H,I). Parafurcal area (furcula basis) with 4-5 neosminthuroid chaetae plus two cup sensilla ( Figure 22). Small abdomen with three blunt acanthoid chaetae on the dorsal anal valve (ms1, ms2 and ms4 on females, ms1, ms2 and mps1 on males), plus three cup sensilla (as4, as5 and a1 on both genders), mi1 on ventral anal valves of females also as a blunt acanthoid chaeta (Figure 23). Diagnosis: Specimens mostly brownish, with a light sword image on dorso-anterior large abdomen ( Figure 19). Ant III with 10, Ant II with two cup sensilla, Ant I with seven regular subequal chaetae ( Figure 20A-C). Head clypeal area with 4-5 unpaired central chaetae and two, one, two, one cup sensilla on lines b, c, e and f, respectively, line f with one acanthoid chaeta laterally to antennal basis ( Figure 20D,E). Sublobal plate with one chaeta-like appendage ( Figure 20K). Labial papillae with five proximal chaetae ( Figure 20L). Epicoxae II-III with one acanthoid chaeta each; femurs II-III with one oval organ each, tibiotarsi I-III with four each; tibiotarsi I-III with five cup sensilla each ( Figure 21A-C). Collophore with two chaetae on each side, tenaculum with two chaetae on each side. Manubrium with nine dorsal chaetae on each side ( Figure 21G). Dens dorsally with 25 chaetae; dens ventral formula from apex to the basis as: 4,2,1,1,0,0,1 ( Figure 21H,I). Parafurcal area (furcula basis) with 4-5 neosminthuroid chaetae plus two cup sensilla ( Figure 22). Small abdomen with three blunt acanthoid chaetae on the dorsal anal valve (ms1, ms2 and ms4 on females, ms1, ms2 and mps1 on males), plus three cup sensilla (as4, as5 and a1 on both genders), mi1 on ventral anal valves of females also as a blunt acanthoid chaeta ( Figure 23).
Description: Body (head + trunk) length of type series ranging between 0.79 and 1.2 mm, males average 0.87 mm, females average 0.82 mm, holotype with 1.2 mm. Habitus typical of the genus. Body and appendages with different types of chaetae as presented in Figure 18. Body color in ethanol mottled brown, darker and more uniform on antennae, lateral head and trunk, femurs and tibiotarsi, without pigments on the surrounding region of the eyes and furcula; dorsally lighter and spottier, with an inverted sword image on anterior region of the large abdomen ( Figure 19). Body chaetae smooth and acuminate, with the exception of few chaetae on small anal valves.
Head (Figures 19 and 20): Antennae shorter than body, with 0.66 mm in the holotype (Figure 19). Holotype antennal segments ratio of Ant I:II:III:IV as 1:3:11.8:2.2. Ant IV with about 54 regular chaetae plus a small subapical "mushroom-like" organ ( Figure 20A). Ant III with a constriction in the basal 2/5, almost subsegmented, with 58 regular chaetae plus 10 cup sensilla, apical organ typical with two sense rods inside a single invagination, accessory microsensillum present ( Figure 20A,B). Ant. II with 20 regular chaetae plus two cup sensilla ( Figure 20C). Ant I with seven regular chaetae, subequal in size ( Figure 20C). Head length (eyes to mouth) of holotype 312 µm. Clypeal area a-f lines with 8/7(+1)/4/4(+1)/3(+1)/5(+1) chaetae respectively, two extra chaetae with unclear homologies (circled), one of them unpaired; b, c, e and f lines with two, one, two, one cup sensilla, respectively; f line with one lateral acanthoid chaeta, near to the antennal basis ( Figure 20D-F). Interantennal area α, β and γ lines with two, two, one short chaetae, respectively, three small pseudopore-like organs present nearby to the α line; frontal area with only A, D and E lines, with two, three, three short chaetae, respectively; E line with one small cup sensillum behind the eyes; eyes 8 + 8, with two interocular chaetae ( Figure 20D). Distal margin of the clypeus with three prelabral chaetae, labral chaetotaxy with 2(+1) p, 2 (+1) m and two a chaetae, a2 as an almost blunt chaeta (somehow spiniform), m1 larger than all other labral chaetae; four labral crests present, the two internal apically subdivided; labrum without clear formed papillae (Figure 20D,G,H). Mandibles asymmetrical with 5-6 apical incisive teeth ( Figure 20I); maxillae typical with six lamellae ( Figure 20J); maxillary outer lobe with apical chaeta about three times longer than the basal one, sublobal plate with one inner chaeta-like appendage plus an outer short cuticular projection ( Figure 20K). Ventral groove with two surrounding chaetae from lines a and b, labial basomedian field projected laterally with four central (one larger than the others) and three lateral chaetae, basolateral field with two subequal chaetae ( Figure 20F). Labial palp with five proximal subequal chaetae, labial papilla formula of guard chaetae as H (2)    Large abdomen appendages ( Figure 21): Epicoxa, subcoxa and coxa I with zero, one, zero chaetae, respectively; trochanter I with four chaetae; femur I with 11 regular chaetae plus one microsensillum and one cup sensillum; tibiotarsus I with 44 regular chaetae (seven of them in the inner side thicker, proximal Fpae, Fppe and Fse↓ present), plus five cup sensilla (one of them as proximal Fpe) and four oval organs (O4ae, O4pe, O3pe and O2pe), distal whorl with eight chaetae ( Figure 21A). Epicoxa, subcoxa and coxa II with one, one, three chaetae, respectively, epicoxa chaeta acanthoid; trochanter II with 4-5 chaetae; femur II with 14 regular chaetae plus one microsensillum, one cup sensillum and one oval organ; tibiotarsus II with 44 regular chaetae (seven of them in the inner side thicker, proximal Fpae, Fppe and Fse↓ present), plus five cup sensilla (one of them as proximal Fpe) and four oval organs (O4ae, O4pe, O3pe and O2pe), distal whorl with eight normal chaetae ( Figure 21B). Epicoxa, subcoxa and coxa III with one, one, four chaetae, respectively, epicoxa chaeta acanthoid; trochanter III with six chaetae; femur III with 12 regular chaetae plus one microsensillum, one cup sensillum and one oval organ; tibiotarsus III with 41-44 chaetae (11-12 of them in the inner side thicker, proximal Fpae, Fppe and Fse↓ present), plus five cup sensilla (one of them as proximal Fpe) and four oval organs (O4ae, O4pe, O3pe and O2pe), distal whorl with eight chaetae ( Figure 21C). Foot complexes I-III with two pretarsal chaetae each, one anterior and one posterior; ungues without cavity with two unpaired inner teeth subequal in size, lateral lamellae without teeth, pseudonychia present, merged to the dorsal face with two dorsal teeth, the distal one smaller, ending in a subapical projection, with lateral margins irregularly serrate, tunica present at the apex of the ungues ( Figure 21D-F). Unguiculi trilamellate without the postero-internal lamella, with two teeth on antero-internal lamella, proximal one enlarged; unguiculi with filament on the posterior lamella, nearside the apical tooth, unguiculus I filament surpassing the unguis apex, shorter on unguiculi II and III. Collophore corpus with one posterior chaeta on each side, plus one distal chaeta on each lateral flap, with a pair of warty sacs. Tenaculum with three teeth on each ramus plus the basal tubercle, with two chaetae on each side of the corpus. Furcal size length in holotype as: manubrium = 74 µm; dens = 249 µm; and mucro = 79 µm. Manubrium with nine dorsal chaetae on each side ( Figure 21G); dens dorsally (posteriorly) with 25 chaetae on the dorsal, inner and outer lines of chaetae combined, one proximal longer than others ( Figure 21H); dens ventrally (anteriorly) with nine chaetae, with the following formula from the apex to the basis: 4,2,1,1,0,0,1 ( Figure 21I); mucro with narrow apex, with both edges serrated, with about 20 teeth on each edge ( Figure 21H,I). Ratio mucro: dens: manubrium in holotype 1:3.4:1.07.
Etymology: The new species was named after the sword-like image on its dorsum (from Latin gladius = sword).
Habitat: Calvatomina gladiata sp. nov. specimens were collected from "Mata dos Saguis", a small forested area within the Biosciences Center of the Federal University of Rio Grande do Norte campus, Natal, Rio Grande do Norte state, Brazil (Figure 1). Further data on the area is presented in [44]. It is the same type locality of the recent described Brachystomella nordestina Souza, Bellini and Weiner, 2018 [44] and Lepidocyrtinus dapeste (Santos and Bellini, 2018) [44].
The new species fits the rufescens-group due to the presence of only three unpaired basal chaetae on the ventral dens and ms1(a0) as a blunt acanthoid chaeta [4,18,37]. There are three species from the rufescens-group recorded in the Neotropical region: C. guyanensis, C. rufescens and now C. gladiata sp. nov. Outside the Neotropical Region, three other taxa from this group are similar to the new species: C. cruciata, C. pallida (Yosii, 1969) [37] and C. trivandrana, all from India, especially in the overall chaetotaxy of the small abdomen of the female with as1(M), as2(M'), as3(N') and ami1(T) as small regular pointed chaetae (see Nayrolles and Betsch [18], p. 288, table 2). However, the new species clearly differs from the Indian taxa in: dens ventrally with four chaetae at the apex (vs. 2-3), dorsal dens with 25 chaetae (vs. [23][24], Ant III with 10 and Ant II with two cup sensilla, respectively (eight and three in C. trivandrana), clypeus with 4-5 unpaired chaetae (six in C. cruciata), collophore with two chaetae per side (one in C. trivandrana), and ms4(H) and mi1(L) on the females small abdomen as blunt acanthoid chaetae (as regular pointed chaetae in C. pallida). Further comparisons among these species are shown in Table 2.   In the new species of Arlesminthurus herein described, there is a bothriotrichum-like sens on the inferior side (Abd IV m line) of the large abdomen ( Figures 5B and 10), which was not described in the other four species of the genus [4,[11][12][13]. Apparently, most of the Bourletiellidae genera are devoid of this bothriotrichum-like sens (e.g., [4,36,48,49]). For instance, this structure is absent in the specimens of Stenognathriopes janssensi Zeppelini and Silva, 2012 [50] analyzed by us, corroborating the original description of the genus (see Betsch and Lasebikan [51], Figure 1A).
Although no representative phylogenetic study of Bourletiellidae using modern methods has been performed so far, Betsch ([36], p. 188) arbitrarily proposed a clade contemplating the genera Bourletiella, Deuterosminthurus and Heterosminthurus. This grouping was based on their simple and conical tibiotarsal spines, unguiculi I-III of similar sizes and tenaculum with two teeth per side (see Betsch [36], p. 174). Except for the obliquely truncate tibiotarsal chaetae [4,57,58], these characteristics are also present in Fasciosminthurus, which was considered by Betsch as a synonym of Prorastriopes Delamare Deboutteville, 1947 [59], and for that reason it was not nominally included in his arbitrary phylogenetic construction (see Betsch [36], p. 175). At that time, three species of Arlesminthurus were already described as Deuterosminthurus (D. aueti, D. richardsi and D. salinensis), and more recently A. franzkafkai plus A. caatinguensis sp. nov. herein described. These five species, and so Arlesminthurus as a whole, also fit into the group proposed by Betsch [36], except for the tenaculum morphology, which is variable, with two or three teeth [4].
In addition to the S-sens of the large abdomen present in at least these five genera (Arlesminthurus, Bourletiella, Deuterosminthurus, Fasciosminthurus and Heterosminthurus), plus unguiculi and distal tibiotarsal spine morphology, such taxa share a denser chaetotaxy, with extra chaetae on the dorsal head (e.g., Figures 8A and 9A) and large abdomen, Ant IV with subapical sensillum and tibiotarsi I-III with three, three and two capitate tenent hairs, respectively [4,36,57,58].
Thus, it is fairly evident that these genera are similar to each other, and for that reason some species were transferred among them according to the evolution of Bourletiellidae's internal taxonomy [4,11,12,36,57,58]. To go further in looking for similarities among Arlesminthurus species it is necessary to investigate if the bothriotrichum-like sens is also present in the other species of the genus, as well as the S-sens in other species of the Bourletiellidae genera, and to make sure whether both structures share the same morphology and could be considered as the same. We believe this feature could carry a strong phylogenetic signal within the Bourletiellidae.

On the Differential Chaetotaxy of Calvatomina Species
As noted by Yosii [8], the chaetotaxy of the small abdomen of females is the main feature used to separate Calvatomina species, as the color patterns could be insufficient or misleading. The displacement and morphology of such chaetae are of diagnostic importance among most Appendiciphora [3,4,36,43], and they were used in posterior studies not only to distinguish Calvatomina taxa, but also to divide the genus into species groups [4,18,37,60]. Another important diagnostic feature noted by Yosii [37] was the ventral chaetotaxy of the dens. Although the number of apical chaetae may be subject to different interpretations, the number and position of basal unpaired chaetae (1,1,0,0,1 or 1,1,1,0,1) provide clear data to compare the species, and they were used by Yosii [37] to separate the bougainvilleae-group and Pseudodicyrtomina Stach, 1957 [60] from the rufescens and formosana groups (a further discussion on such groups is presented in the next topic). The comparative Table 2 endorses such data as important diagnostic features.
Our revision of the Neotropical Calvatomina, specially the comparison between detailed described species as C. gladiata sp. nov. and C. guyanensis, suggested other easily accessible data which are useful in order to compare them. The number of cup sensilla on Ant. II, III and the clypeal area, the presence of a short acanthoid chaeta lateral to the antennal basis and even the number of clypeal unpaired chaetae proved to be helpful features to distinguish the species (see Table 2). Since the head chaetotaxy of the Dicyrtomidae is remarkably easier to understand compared to other taxa like Sminthurinae, due to the presence of fewer chaetae [30], the clypeal data can be used as reliable and clear diagnostic elements. Our previous studies also suggested that the morphology of the maxillary outer lobe and the sublobal plate and the number of proximal labial chaetae can be useful in separating closely related genera of Symphypleona and even species within the same genus, a result seen in other revisions as well [25,43,61,62]. For this reason we included this information in the diagnosis of C. gladiata sp. nov and such data should be investigated in further species of the genus and of the Dicyrtomidae.
Other features which may be useful in delimiting Calvatomina species are the number of cup sensilla on the tibiotarsi (a characteristic we dismissed in Table 2 since it was not entirely available for any other compared species) and the number of ventral tube, tenaculum and manubrial chaetae. For instance, on the tibiotarsus I of the new species and C. tesselata (Snider, 1990) [63] there are five cup sensilla, whereas in C. guyanensis apparently there are four, as well as in C. sylvestratilis (Snider, 1990) [63], C. bellingeri (Snider, 1990) [63], C. madestris (Snider, 1990) [63] and C. microdentata (Snider, 1990) [63], and only three in C. longidigita (Snider, 1990) [63]. Furthermore, as pointed in Snider [63], the parafurcal area chaetotaxy may be quite variable among different species of the genus.
As discussed in Nayrolles and Betsch [18], the chaetotaxy of the appendages and at least of the small abdomen has additions during the development from juveniles to the adults of Calvatomina. Therefore, the reduction in the number of some elements, such as on the collophore, tenaculum and furcula, may represent a type of pedomorphosis, a hypothesis which should be investigated in further species other than C. guyanensis.

On the Validity of Calvatomina Internal Groups
Yosii [37] divided Calvatomina into three groups of species (bougainvilleae, rufescens and formosana). The sole feature to separate the bougainvilleae-group from the others was the dens with 1,1,1,0,1 proximal ventral chaetae (vs. 1,1,0,0,1 in the other two groups). Yosii also suggested that such groups represent natural taxa (Yosii [37], p. 226). However, the ventral dental chaetotaxy formula of the bougainvilleae-group is not exclusive to it, since it is shared with other Dicyrtominae, at least with Pseudodicyrtomina [4,37,60]. Among the species of the bougainvilleae-group there is no clear and exclusive pattern in the females' small abdomen chaetotaxy. For instance, its species may present ms1(a0) as a blunt acanthoid (as in C. christianseni and C. discolor sensu Mari-Mutt) or as a regular pointed chaeta (as in C. bougainvilleae, see Yosii [39], p. 37 and Yosii [37], pp. 228-229). Thus, the morphology of a0, which is the sole feature proposed to separate the rufescens from the formosana-group, is polymorphic within the bougainvilleae-group. Our revision of the Neotropical species shows that there is no clear diagnostic feature shared between C. discolor sensu Mari-Mutt and C. christianseni, which are exclusive to this group, other than this ventral extra chaeta on the dens (see Table 2). The finding of C. rufescens (from the rufescens-group) and C. discolor sensu Mari-Mutt from Colombia, which are remarkably similar in several diagnostic characteristics, with the exception of ms4(H) and mi1(L) chaetae on the female's small abdomen and ventral dens chaetotaxy, also suggest that species from different groups could actually be closely related (see Mari-Mutt [16], p. 379). Therefore, the separation of the bougainvilleae-group from the others based on a single dental ventral chaeta, without the support of any other clearly exclusive characteristic, may be arbitrary. As a matter of fact, Yosii [37] did not explain clearly why such characteristics were used to split Calvatomina into species-groups, other than their usability.
Distribution does not clearly support Yosii's groups either. The three groups were found in the Neotropical Region: C. discolor and C. christianseni from the bougainvilleaegroup; C. nymphascopula, with a similar color pattern to the previous species but from the formosana-group; and as remarked before, C. rufescens, C. guyanensis and C. gladiata sp. nov. from the rufescens-group. The Hawaiian species, although most likely introduced, are represented by the three groups as well [63][64][65], which is also the case for the Calvatomina fauna from the Solomon Islands [37]. With such an overlapping distribution, there is no clear biogeographic evidence supporting a vicariant speciation of the internal groups of Calvatomina.
In this sense and considering the previous notes, we believe the species groups of Calvatomina described by Yosii [37] could be artificial and must be studied from a phylogenetic perspective, even if these groups can be handy for comparisons of species.

Conclusions
After our study, Arlesminthurus now has five and Calvatomina has 35 described species, respectively, with all Arlesminthurus and six Calvatomina taxa recorded in Neotropical regions. We expect that the detailed analyses of the morphology of both species, especially of Arlesminthurus caatinguensis sp. nov., may provide further foundations for the comparative studies of the Bourletiellidae and Dicyrtomidae. The observation of Arlesminthurus caatinguensis sp. nov. large abdomen chaetotaxy, with a bothriotrichum-like sens which is quite likely homologous to the S-sens seen in other bourletiellid genera, reinforces the importance of the study of the whole body chaetotaxy for the Symphypleona, a feature that is dismissed in several taxonomic studies.