A new genus of flower-dwelling melicharid mites (Acari: Mesostigmata: Ascoidea) phoretic on bats and insects in Costa Rica and Brazil Author Lindquist, Evert E. Author Moraza, Maria L. text Zootaxa 2008 1685 1 37 journal article 10.5281/zenodo.180479 d1874f7a-7d67-4f0d-8e5e-16c18ececf86 1175-5326 180479 Spadiseius , new genus ( Figs. 1–69 ) Type species: Spadiseius calyptrogynae new species . Genus based on adult female, male and immature instar material representing two newly described species, and on adult females and males of four undescribed species. Diagnosis. Nymphs and adults of Spadiseius share the following apomorphies with other genera included in the family Melicharidae : fixed chela with pilus dentilis modified from a setiform structure into an expanded hyaline lobe or flap (autapomorphic); movable chela (except for adult male) with a ventral mucro near its base (autapomorphic); peritrematal shield narrowly connected to or free posteriorly from exopodal plate beside coxa IV (homoplastic). They are distinguished apomorphically from those of other melicharid genera by the following three attributes. Dorsal shield of deutonymphs and adults somewhat hypertrichous, with one to several pairs of supernumerary setae inserted symmetrically near setae j6 and sometimes among setae z3–z5 , s3– s5 on the anterior region and sometimes asymmetrically among setae J1–J4 on the posterior region. Dorsal shield of adult male with some to many of the peripheral setae of z–Z , s–S and r–R series enlarged dimorphically to form a variably well developed corona of basally thick and apically clavate or capitate or attenuate setae (those of female usually uniformly short, simple). Femur IV of deutonymph and adult female with dorsal seta ad-1 thick, untapered, oar-like, in distinction to adjacent tapered setae. Other attributes include: dorsal shield of adults with lateral margins entire and with setae z3 present; adult female with setae st1–st3 on sternal shield ( st3 sometimes inserted on a posteriorly desclerotized region of this shield), st4 with sternal poroids 3 inserted on soft cuticle, st5 and paragenital poroids iv5 inserted on soft cuticle alongside genital shield, and with obovate to nearly inversely subtriangular (rather than ovate or elliptical or subcircular) anal shield with gland pores gv3 ; adult male with sternitigenital shield slightly narrowed and not consolidated with endopodal strips between coxae IV, and with weakly sclerotized ventrianal shield; setae st5 usually attenuated, longer than st1–4 , and sometimes inserted on soft cuticle closely alongside sternitigenital shield, both sexes with relatively small anal opening (euanal setae and anal poroids on anal valves absent). Both sexes with anterior margin of tectum pointed or narrowly rounded, smooth or slightly serrated. Leg II of male with ventral setae unmodified on femur, but with av-1 , av-2 and sometimes mv short, spine-like on tarsus. Description. Adult. Idiosomal dorsum . Dorsal shield of adults entire, without lateral incisions, ornamented with reticula on female and sometimes also with wart-like, seta-bearing thickenings on male, and lacking a delineated marginal rim laterally where marginal setae are inserted. Dorsum with approximately 45– 60 pairs of setae, most (including some of r– series and rarely even R1–R2 ) inserted on dorsal shield, but usually R– and UR– series, r5 , and sometimes r4 on soft cuticle in adult female and some of R– and UR– setae variably off shield in adult male; z3 present; submarginal UR– series with few setae present on deutonymph and adult; dorsal shield mildly hypertrichous, usually with a pair of extra setae near j6, variably with 2 or 3 extra pairs amidst z– and s– series on podonotal region, and sometimes with several paired or asymmetrically unpaired setae amidst J– series on opisthonotal region. Dorsal setae of adult female usually mostly uniform in simple form (sometimes slightly knobbed at base, or untapered and rod-like) and moderately short length (except Z5 sometimes longer and apically capitate), J5 smaller than others ( Figs. 18 , 46 ); dorsal setae of adult male highly dimorphic, with those in central region of shield either very short, simple (similar to J5 ), and sometimes inserted on wart-like thickenings, or moderately short and thickened blade-like, while some to most peripheral setae are enlarged, of variable lengths, and either attenuated or with thick shafts and capitate or clavate apices, many of them inserted on tubercles ( Figs. 21 , 23 , 51–53 ). Dorsal shield with complement of 23 pairs of discernible pore-like structures (9 podonotal, 14 opisthonotal), of which 7 (4 podonotal, 3 opisthonotal) superficially appear secretory (gland pores) and 16 (5 podonotal, 11 opisthonotal) non-secretory (poroids) ( Fig. 18 ); marginal poroid Rp (= idR3 ) between setae R3–R4 on soft cuticle in female but sometimes on edge of shield in male. Peritrematal plates uniting with dorsal shield anteriorly at level between setae s1 and r2 on adult female and between r2 and r5 on adult male; peritremes well developed, interspecifically variable in length, reaching anteriorly at least to level of setae r5 . Anterior to dorsal shield, vertical region with pair of plates (often difficult to discern, not illustrated) above bases of legs I and sometimes touching dorsal shield at level of paravertical setae z1 . Idiosomal venter . ADULT FEMALE. Sternal shield entire, sometimes desclerotized posteriorly behind level of poroids 2, with 3 pairs of setae ( st3 inserted in often desclerotized area), 2 pairs of poroids and continuous with endopodal extensions between coxae I and II, weakly between II and III. Metasternal plates absent, fourth pair of sternal setae with third pair of sternal poroids on soft cuticle ( Figs. 19 , 47 ). Endopodal strips weakly developed or vestigial between coxae III and IV. Genital shield with hyaline anterior margin broadly rounded, extending to level of third sternal poroids and usually not overlapping posterior margin of sternal shield; posterior margin of genital shield broadly rounded; genital setae st5 and poroids iv5 inserted on soft cuticle flanking shield. Postgenital furrow weakly formed, with or without a strip of 2 or 4 weakly sclerotized platelets. Inguinal region with 1 or 2 pairs of metapodal platelets, the smaller pair difficult to discern, and gland pores gv2 and gp2 on exopodal rim behind coxae IV. Anal shield relatively small, obovate or nearly inversely subtriangular, with anal opening not enlarged; adanal gland pores on lateral edges of shield at level of posterior margin of anal opening; cribrum normally developed. Opisthogaster with 8 to 10 pairs of simple setae on soft cuticle around anal shield ( JV1–JV5, ZV1–ZV5 , but sometimes without ZV3 and one of other ZV setae; a UR seta may appear like another ZV pair), SV series absent. Peritrematal region on each side with 2 gland pores and 4 poroids; peritrematal plate with poroid ip1 inserted on its dorsal edge laterad seta s2 , gland pore gp1 and adjacent poroid ip2 inserted on its dorsal edge at level between coxae II and III ( Fig. 18 ), and with poroid ip3 appressed to posterior edge of stigmata ( Fig. 19 ); peritrematal plate lacking any posterior extension, such that poststigmatic poroid ip4 inserted on soft cuticle and gland pore gp2 inserted on exopodal rim posterolaterad coxa IV. Exopodal strips weakly sclerotized alongside peritrematal shield, with projections between coxae I and II, II and III, III and IV. Spermathecal apparatus without distinctly sclerotized structures, but with a usually discernible tubular conduit leading from solenostome between bases of legs III–IV to a visibly denser calyx and hyaline vesicle. ADULT MALE. Sternogenital shield with 4 or 5 pairs of setae and 3 pairs of poroids, united with endopodal strips between coxae I–II and II–III, but free from weak strips between coxae III–IV; posterior margin of shield prominent, convex or bilobate, contiguous with or overlapping, but not consolidated with anterior margin of ventrianal shield; setae st5 longer than st1–4 , and sometimes inserted on soft cuticle when posterolateral corners of shield constricted; paragenital poroids iv5 on soft cuticle beside posterolateral corners of shield ( Figs. 22 , 58 ). Opisthogaster with ventrianal shield weakly sclerotized other than in anal shield area, overrunning lateral areas occupied by metapodal platelets, and with 6 or usually 7 pairs of ventral setae in addition to circumanal setae; setae JV5 and, if present, ZV5 inserted on soft cuticle. Ventrianal shield free from peritrematal and expodal plates; cribrum as in adult female. Exopodal and peritrematal shielding, and peritremes as in adult female. Gnathosoma . Tectum with anterior margin triangular, pointed or narrowly rounded apically, smooth or slightly serrated ( Fig. 7 ). Fixed cheliceral digit of adult female with 3 to 5 small teeth subapically, that of adult male with 2 to 4 teeth, both sexes with pilus dentilis expanded into a hyaline pointed lobe (instead of setiform) antiaxially, and with hyaline rim smooth, unfringed along its paraxial face above base of movable chela; movable chela of female with 1 or 2 small teeth and with ventral mucro near base ( Fig. 8 ); movable chela of male edentate, without ventral mucro, with hyaline envelope at its base more strongly fringed than in female, and with spermatodactyl directed anteriorly, simple or distinctively shaped in form ( Figs. 27 , 55 ). Corniculi of adult female with prominent longitudinal keel or carina on ventral face ( Fig. 59 ) and with variably convergent simple apices ( Figs. 1 , 59 ), those of adult male similarly formed but more widely spaced, usually less convergent ( Fig. 26 ); internal malae slender, pointed, finely fringed in the female, broader, coarsely fringed and bifid apically in the male, not extending beyond tips of corniculi; salivary stylets split apically ( Figs. 1, 3 , 59, 60 ); labrum prominent, blade–like, projecting slightly beyond apices of corniculi, with smooth lateral margins ( Fig. 2 ). Deutosternum with 7 or 8 rows of subequally moderately narrow denticles, all rows connected. Palpi with normal setation and setal ontogeny as described for Gamasina by Evans (1964) , including only one seta on palptrochanter of protonymph; palpfemoral seta al spatulate, palpgenual seta al-2 tapered or spatulate, and palpgenual seta al-1 tapered; palptarsal apotele two-tined ( Fig. 5 ). Legs . Legs I to IV with paired claws and rounded pulvilli well developed, inserted on well developed pretarsi. Legs of moderate length, I and IV no longer than dorsal shield. Ventral face of coxae I with serrated ridges and with six coxal glands, 2 anteriorly and 4 posteriorly ( Fig. 64 ). Tarsus I with sensilla s inconspicuous, not lanceolate or elongate ( Figs. 61–63 ). Tarsi II–IV with apical setal processes ad-1 , pd-1 inconspicuous, less than half as long as pretarsi ( Figs. 28 , 34 ). Complement of setae and their ontogeny on segments of legs I to IV normal for Melicharidae (as presented by Lindquist & Evans 1965 for Melicharini), setation of genua of legs I-II-III-IV, respectively, usually 13-11-9-9 , but genu IV sometimes with 10 setae when pl-2 asymmetrically or pseudosymmetrically present; that of tibia usually 13-10-8-10 ( pl-2 absent on tibia III), but tibia I sometimes with 12 setae when v-3 asymmetrically or pseudosymmetrically absent. Femora I–IV with dorsal seta ad-1 thickened, less tapered than adjacent setae, usually progressively longer on legs I to IV, oarlike on femur IV and sometimes on femora I–III ( Figs. 30–33 ), more enlarged on male than female ( Figs. 66– 69 ); femur II ventral setae unmodified on female and male; other leg setae (apart from dorsoapical sensory cluster on tarsus I) simple, unmodified on female, but many setae on dorsal and lateral faces of femora, genua and tibia thickened and blunt-tipped or clavate on adult male. Tarsus II of male also with dimorphically modified setae, including av-1 , av-2 , and sometimes av-3 ( mv ) short, spine-like ( Fig. 28 ). Tarsi III–IV of adult male without knob- or spine-like setae, but with ventral setae more attenuate than on female. Deutonymph . Idiosomal dorsum. Dorsal shield with lateral incisions (sometimes indistinct) reaching to, or slightly mediad, level of setae Z1 , and with approximately 35 to 40 pairs of setae: about 16–18 pairs ( j1–j6, z2–z6, s3–s6 , and 1 to 3 pairs of extra setae) on podonotal region, and 15–18 pairs ( J1–J5, Z1–Z5, S1–S5 , and sometimes a few paired or asymmetrically unpaired setae amidst J series) on opisthonotal region ( Figs. 16 , 42 ). Soft cuticle with z1, s1–s2, r2–r5 on podonotal region and R1–R6 and 2 or 3 pairs of UR– setae on opisthonotal region. Dorsal setae added to protonymphal complement denoted without parentheses in Figs. 16 , 42 . Dorsal idiosomal complement of poroids and gland-pores similar to that in female; paravertical poroids ipz1 added to protonymphal complement. Idiosomal venter. Sternal shield with endopodal extensions between coxae I–II and II–III but not between III–IV, and with 4 pairs of setae and 3 pairs of poroids; setae st5 and paragenital poroids inserted on soft cuticle at level of posterior margin of shield ( Figs. 17 , 43 ). Anal shield subcircular; adanal pores on lateral edges of shield at level of posterior margin of anal opening; cribrum as in adult female. Opisthogaster with 8 to 10 pairs of ventral setae ( JV1–JV5 , ZV1–ZV3 and sometimes ZV4, ZV5 ) plus 1 or 2 adjacent UR– setae; ventral setae added to protonymphal compliment denoted without parentheses in Figs. 17 , 43 ; ZV4, ZV5 sometimes absent. Peritrematal shields not uniting with dorsal shield. Poststigmatic poroid ip3 contiguous with stigma on posterior edge of peritrematal shield, poststigmatic poroid ip4 on soft cuticle; poroid ip2 and gland pore gp1 near midlength of peritreme between coxae II and III on soft cuticle. Rim of exopodal plates behind coxae IV well delineated, with gland pore gv2 at its medial extremity. Gnathosoma . Tectum, chelicerae, salivary stylets, corniculi, deutosternal structures and palpi similar to those in adult female. Legs. Pretarsi, claws, and chaetotaxy of legs I–IV as in adult, including these additions to protonymphal setal complement: ad-3 on femora I–IV, v-3 on femora I–II, al-2 on femur II; al-2 on genua I–IV, ad-3 on genu I, ad-2 on genu IV, pd-3 on genua I and IV, pl-2 on genua I–III, pl-1 and rarely pl-2 on genu IV, usually av-2 on genu I, av-1 on genua II–IV, pv-1 on genua II–III; al-2 on tibiae I–IV, ad-3 on tibia I, ad-2 on tibia II, pd-3 on tibiae I and IV, pl-2 on tibiae I, II, IV, usually av-2 on tibia I. Femora I–IV with dorsal seta ad-1 thickened, less tapered than adjacent setae, usually progressively longer on legs I to IV, oar-like on femur IV and sometimes on femora I–III ( Figs. 44, 45 ). Protonymph . Idiosomal dorsum. Body dorsum with sclerotized podonotal and pygidial shields, and with 30 pairs of setae: 11 pairs on podonotal shield, 4 pairs on lateral soft cuticle beside podonotal shield, 7 pairs on interscutal soft cuticle, and 8 pairs on pygidial shield; dorsal setae added to larval complement denoted without parentheses in Fig. 13 . Mesonotal scutellae weakly sclerotized as 3 pairs of sigillae laterad setae J1–J2 . Body dorsum with complement of 22 pairs of discernible pore-like structures, of which 15 (3–4 on podonotal shield, 6–7 on soft cuticle, 5 on pygidial shield) non-secretory (poroids) and 7 (4 on podonotal shield, 1 on soft cuticle, 2 on pygidial shield) superficially appear to be secretory (gland pores). Peritrematal region on each side with 5 or 6 pore-like structures, of which 3 poroids and 2 or 3 appear to be gland pores. Idiosomal venter. Sternal shield with endopodal extensions between coxae I–II and II–III, with 3 pairs of setae and 2 pairs of poroids (third pair absent); setae st5 inserted on soft cuticle at level of posterior margins of legs IV ( Fig. 14 ). Anal shield, circumanal setae, adanal pores, and cribrum similar in form, size and position to those on deutonymph. Opisthogaster with 4 pairs of ventral setae on soft cuticle around anal shield. Poststigmatic poroid and gland pore, and poroid and gland pore anterior to apex of peritreme between coxae II and III on soft cuticle. Exopodal plates indiscernible. Gnathosoma . Tectum more broadly triangular and bluntly pointed than in deutonymph ( Fig. 15 ); other gnathosomatic structures similar to those in deutonymph, except palpi with normal protonymphal complement of setae (see Evans 1964 ), including only 1 trochanter seta. Legs. Legs I-II-III-IV with pretarsi, well-developed claws, and with normal protonymphal complement of setae as described for Ascidae by Lindquist and Evans (1965) : coxae, 2-2-2-1; trochanters 4-4-4-4; femora 10- 8-5-4 , including pv added to larval complement on femur II; genua 8-6-6-5; tibiae 8-7-7-7. Femora I–IV with dorsal seta ad-1 thicker, less tapered than adjacent simple setae, and sometimes rod- or oar-like ( Figs. 40, 41 ). Larva. Idiosomal dorsum. Body dorsum with sclerotized podonotal and pygidial shields, and with 12 pairs of setae plus alveolar rudiments of 3 other pairs: 9 pairs of setae on podonotal shield (denoted in Fig. 10 ), 3 pairs of setae ( s6, S3, S4 ) plus alveolar rudiments of 2 other pairs ( J2, J3 ) on soft interscutal cuticle, and 2 pairs of setae ( Z3, Z4 ) plus alveolar rudiments of 2 other pairs ( J4, J5 ) on pygidial shield. Setae S5 and Z5 present on soft cuticle ventrolaterally ( Fig. 11 ). Body dorsum with complement of 16 pairs of discernible pore-like structures, of which 12 (4 on podonotal shield, 5 on soft cuticle, 3 on pygidial shield) superficially appear to be non-secretory (poroids) and 4 (2 on podonotal shield, 1 on soft cuticle, 1 on pygidial shield) secretory (gland pores). Idiosomal venter. Sternal shield with endopodal extensions between coxae I–II and slightly between II– III, with 3 pairs of setae and 2 pairs of poroids (third pair absent); pair of subcutaneous structures evident at level of posterior margins of coxae III ( Fig. 11 ). Anal shield oval, with para-anal setae longer than postanal seta; anal valves lacking euanal setae and their alveolar rudiments; cribrum absent. Opisthogaster with 3 or 4 pairs of ventral setae ( JV1, JV2, JV5, sometimes ZV2 ) plus setae S5 and Z5 on soft cuticle around anal shield. Gnathosoma . Tectum broadly, irregularly triangular ( Fig. 12 ). Fixed digit of chelicera with dentition and pilus dentilis lobe as in protonymph; movable chela edentate or with one minute tooth, and with ventral mucro ( Fig. 37 ). Subcapitulum with salivary stylets, corniculi, internal malae and rows of deutosternal denticles as in protonymph; with 2 pairs of hypostomatic setae. Palpi with normal larval complement of setae, including none on trochanter, as described for Gamasina (see Evans 1964 ). Legs. Legs I-II-III with pretarsi, well-developed claws, and with normal larval complement of setae as described for Ascidae by Lindquist and Evans (1965) : coxae, 2-2-2; trochanters 4-4-4; femora 10-7-5 ; genua 8-6-6; tibiae 8-7-7. Femora I–III with dorsal seta ad-1 either slightly more thick and less tapered or untapered and rod- or oar-like in contrast to adjacent femoral setae ( Figs. 38, 39 ). Etymology . The name of the genus is a Latinized combination of the botanical term spadix , a rod-like spike bearing minute flowers usually enclosed within a sheath-like spathe on the same axis, and derived from Latin, based on a Greek word meaning a torn-off branch or frond, especially of a palm, and seius or sejus , a Roman surname used by many authors to form names for genera of mesostigmatic mites. The name is masculine in gender, and is intended to refer to the spadix- or spike-like form of inflorescences of aroids and palms harboring these mites. Distribution and habitats . Material available of this genus is associated with aroid and palm inflorescences and their pollinators from just two localities in Costa Rica and Brazil . Collection details for the two described species are presented with the description of each species, below. Data given on the slide labels of the four undescribed species are as follows: Spadiseius sp. 3, 5 females, 1 male : Costa Rica , Heredia Province, La Selva Biological Station ( 10° 26' 1" N , 84° 1' 2" W ) elevation 50–150 m , 1–29 June 1997 , coll. E.E. Lindquist, ex “Palmae” ( Arecaceae ). Spadiseius sp. 4, 1 female, 1 male : Brazil , São Paulo State, Pariquera-Açu area ( 24° 36' S , 47° 53' W ), 17 January 2000 , coll. L.V.F. Silva, ex Arecaceae , terminal shoot of Astrocaryum aculeatissimum (Schott) Burret. Spadiseius sp. 5, 2 females: Brazil , São Paulo State, Pariquera-Açu area ( 24° 36' S , 47° 53' W ), 19 January 2000 , coll. L.V.F. Silva, ex Arecaceae , flowers of Euterpe edulis Mart. Spadiseius sp. 6, 1 female: Brazil , São Paulo State, Pariquera-Açu, 19 January 2000 , coll. L.V.F. Silva, ex Arecaceae , flowers of Euterpe edulis Mart. Specimens of species 5 and 6 have the same collection data, but whether they were from different flowers of the same host or coexistent in the same flowers is uncertain. Remarks . As noted in the diagnosis, the genus Spadiseius is based on three apomorphies, all of which appear to be unique, or autapomorphic, among the known taxa of Melicharidae : (1) the presence of supernumerary setae in specific areas of the anterior and sometimes the posterior regions of the dorsal shield in deutonymphs and adults; (2) some to many of the peripheral setae of the dorsal shield enlarged dimorphically to form a corona of attenuate or clavate or capitate setae in adult males, in contrast to their generally simple setal counterparts in females; and (3) femora I–IV of nymphs and adults with seta ad-1 thick, poorly tapered, and sometimes rod- or oar-like (generally oar-like on femur IV of deutonymph and adult female), in distinction to adjacent simple setae. Within the known taxa of Melicharidae , Spadiseius seems most closely related to the genera Xanthippe Naskrecki & Colwell (1995) and Rhinoseius Baker & Yunker and Tropicoseius Baker & Yunker sensu Naskrecki & Colwell (1998) , based on the shared derived attribute of setae av-1 , av-2 , and sometimes av-3 (also denoted as mv ) modified as stout, spine-like structures on tarsus II of adult males. Xanthippe is based on but two species, which live in inflorescences of the same species of palm, Socratea exorrhiza , in Venezuela , and whose adult females are phoretic on pollinating beetles of the nitidulid genus Mystrops . This taxon is thought to represent the sister group (or immediate outgroup) of the also Neotropical flower-dwelling genera Rhinoseius and Tropicoseius , whose adult females are phoretic on hummingbirds ( Naskrecki & Colwell 1998 ). Spadiseius is tentatively considered here to be the immediate outgroup of those three genera, as it is plesiomorphic relative to them in its adult males not having enlarged or otherwise modified ventral setae av on the femur, genu, and tibia of leg II, in its adult females and males not retaining a deutonymphal division or lateral incisions on the dorsal shield, and in its deutonymphs and adults retaining setae z3 on the dorsal shield. In a key to world genera of Ascidae presented by Halliday et al. (1998) , the genera comprising Melicharidae sensu Lindquist et al. (in press) track through the second part of couplet 19 to couplets 26 through 33. Other than the dorsal shield of adults being slightly hypertrichous rather than holotrichous, Spadiseius tracks readily through couplet 26 to couplet 28, where an additional couplet may be inserted to account for this genus: 28A(26). Dorsal shield of adults entire, slightly to notably hypertrichous, with one to several pairs of supernumerary setae inserted near setae j6 and sometimes among setae z3–z5 , s3–s5 on anterior region and sometimes among setae J1–J4 on posterior region; femur IV of female with dorsal seta ad-1 untapered, rod-like or oar-like, in distinction to adjacent simple setae; dorsal shield of male with peripheral setae enlarged to form a corona of basally thick and apically clavate or capitate or attenuate setae, in contrast to their generally simple setal counterparts in females .......................... Spadiseius - Dorsal shield of adults entire or with midlateral incisions or rarely completely divided, holotrichous or nearly so, lacking supernumerary setae; femora I–IV of female with dorsal seta ad-1 tapered, not distinguished from adjacent setae; dorsal shield of male with peripheral setae attenuate, sometimes longer than their setal counterparts in females, but not forming a corona of thickened setae ..... 28B 28B (see couplet 28 in Halliday et al. ) The attribute of salivary stylets having split apices, which is evident (but not always readily discernible) in all active instars of members of Spadiseius , has not been noted among other melicharines or less related families of mesostigmatic mites. However, these structures are not routinely accounted for in descriptive taxonomy, and character state alternatives in their form have not been considered. Based on our limited observations among members of other taxa, including species of Rhinoseius , Tropicoseius , Xanthippe , the split condition is clearly apomorphic; however, the taxonomic usefulness of this character is beyond further consideration at present. Similarly, the pair of plates in front of the dorsal shield on the adult female have not been noted in previous descriptions of melicharine or other related mites. These structures may be dorsolateral extensions and expansions of the exopodal strips that extend above the bases of legs I from alongside legs I– IV. Their taxonomic usefulness can not be considered in absence of observations from exemplars of other related taxa. Although mites of the genus Spadiseius are not characterised by having elongated idiosomas, their larvae are notable among melicharine taxa in having the posterior region of the podonotal shield, as delineated between the insertions of setae j5 and j6 , elongated relative to the anterior region between j1 and j5 (i.e., with a ratio of about 1.3 to 1.4, see Fig. 10 ). This disproportionate length is lessened on protonymphs (to about 1.2, Fig. 13 ) and the ratio becomes subequal on deutonymphs and adults. An examination of illustrations shows a similar larval and protonymphal elongation of the posterior podonotal region in Mycolaelaps maxinae Lindquist (1995) , but followed by considerably greater elongation in the anterior region of deutonymphs and adults (the ratio becoming 0.9 or 0.8), all instars of which are elongated for living in the pore tubes of bracket fungi. In contrast, the larvae and protonymphs of freely living species of the melicharine genus Proctolaelaps have the posterior region as delimited by setae j5–j6 consistently subequal to or shorter than the anterior region, with the ratio increasingly favoring the anterior region on deutonymphs and adults (e.g., see illustrations in Bernhard 1963 ). The only other taxa with posterior/anterior podonotal region ratios similar through ontogeny to those of Spadiseius and not having elongated idiosomas are among the few species of the genera Rhinoseius and Tropicoseius ( sensu Naskrecki and Colwell 1998 ) for which the developmental instars have been described (e.g., see illustrations in Hunter 1972 , Micherdzinski & Lukoschus 1980 , Wiese and Fain 1996a , 1996b ). Our observations of an unidentified species of Rhinoseius for which we have a developmental series indicates the same phenomenon, i.e., larval ratio 1.5, protonymph 1.1–1.2, deutonymph and adult 0.7– 0.8. This ontogenetic attribute may be an apomorphy shared between these genera of flower-dwelling melicharines. If so, it will be interesting to determine whether the as-yet undescribed immatures of the genus Xanthippe share it as well.