New Ptiliidae (Coleoptera) from Sarawak in the spirit collection of the Natural History Museum, London

This paper is based on three collections of Ptiliidae from Sarawak totalling more than 2000 specimens made by staff and affi liates of the Natural History Museum, London, between March–July 1978. One new genus Niptella gen. nov with its type species Niptella gutta gen. et sp. nov. and 24 new species are described and fi gured: Sindosium collinsi sp. nov., Bambara hammondi sp. nov., Bambara subtortuosa sp. nov., Bambara tortuosa sp. nov., Erro brookei sp. nov., Cissidium globulum sp. nov., Cissidium longum sp. nov., Cissidium marshallae sp. nov., Cissidium pauxillum sp. nov., Cissidium subfoveolatum sp. nov., Cissidium triangulum sp. nov., Discheramocephalus nigritus sp. nov., Kuschelidium sarawakense sp. nov., Ptinella alisonae sp. nov., Acrotrichis acuta sp. nov., Acrotrichis belli sp. nov., Acrotrichis bidens sp. nov., Acrotrichis geiseri sp. nov., Acrotrichis globosa sp. nov., Acrotrichis hanskii sp. nov., Acrotrichis muluensis sp. nov., Acrotrichis plaga sp. nov., Storicricha resticula sp. nov., Storicricha umbella sp. nov. New records and information are provided for Dipentium latum Darby, 2019; Ptiliola semitaria Darby, 2018; Baeocrara minima Darby, 2019; Acrotrichis agricola Darby, 2019; Acrotrichis britteni Johnson, 1969; Acrotrichis bubalis Darby, 2019; Acrotrichis cognata (Matthews, 1877) and Acrotrichis cursitans (Nietner, 1856).


Introduction
This paper is based on collections of Ptiliidae from Sarawak (Malaysia) by N.M.Collins, March-May 1978 (103 specimens), I. Hanski, April-July 1978 (±1800 specimens), and P.M. Hammond and J. E. Marshall, May-July 1978 (105 specimens) in the spirit collection of the Natural History Museum, London (BMNH).All collectors worked in the Mulu World Heritage Area comprising some 52000 hectares of equatorial rainforest ranging from 50-2377 meters above sea level with many extensive cave systems and a geology including alluvial clays, sandstone and limestone formations all producing a large number of diverse habitats with many endemic species (Chung et al. 2000) (Fig. 1).Although many beetles have been recorded from Sarawak, there do not appear to be any specifi c records of Ptiliidae.

Material and methods
Hanski and Collins confi ned their collecting to pitfall traps, those of the former mostly baited with fi sh and placed at different distances above sea level, whilst Hammond and Marshall concentrated on litter sampling.
After preliminary sorting to families, the insects were transferred into alcohol fi lled vials before being stored in a kilner jar in the Museum's spirit collection.All insects removed during the course of this study have either been mounted for pinning in the general collection or returned to the kilner jar.Recent research was carried out using a Leica M165C stereo microscope, an Olympus BH2 compound microscope fi tted with Phase Contrast, and a Phenom scanning electron microscope.Images and measurements were made using the inbuilt software and cameras of the Phenom, a Leica DFC450 digital camera and associated software attached to the stereo microscope, and a Canon EOS 1100D digital camera with associated software attached to the Olympus microscope.The images were prepared for publication using Helicon stacking software and Corel Paint Shop Pro software care being taken not to alter or obscure any features.All specimens selected for detailed study were subsequently mounted on cards with dissections mounted in Euparal on acrylic sheet pinned with the dry mounted specimens and labels.
As set out in my previous papers the generic and species descriptions rely as much on fi gurative illustration and traditional morphometrics as on literal description, the specifi c intention being to convey as much information as possible for future workers without the need to study type material.Unless otherwise stated the habitus length measurement is taken from the front of the head to the apex of the elytra.Where several specimens are involved this is taken from the holotype or averaged from a series representing the smallest and largest judged by eye.Magnifi cations are those of the original SEM pictures.Colour is that of the mounted specimens, in all cases when not mounted and placed in transmitted light (i.e., in alcohol) most appear much paler.Genera are arranged alphabetically within tribes.As explained below many of the specimens of Acrotrichis Motschulsky, 1848, Storicricha Johnson, 1988, Bambara Vuillet, 1911 and Ptiliola Haldeman, 1848 look very similar in alcohol and require dissection of the genitalia to determine species.This is clearly not possible given the number of specimens involved so that those not selected as holotypes and paratypes for pinning and dissection have been returned to the spirit collection determined where numbers permitted by association and without type designations.
I have had great diffi culty in knowing whether the very faintly written locality information in many of the tubes referred to 'camp' or 'comp' and have rationalized all with comp on the basis that a camp site could be referred to as a type of compartment.
The institutional acronym BMNH used in the taxonomic treatment refers to the Natural History Museum, London (formerly British Museum: Natural History).Genus Sindosium Johnson, 2007 Genus described on the basis of two species: S. foveatum Johnson, 2007 andS. opacipenne Johnson, 2007 from the Solomon Islands.An additional species S. bacchusi Darby, 2019 was subsequently described from Sabah (Darby 2019).The name is an anagram of Nossidium Erichson, 1845 to which genus it shows very close affi nities particularly in the wing shape, male possession of parameres and the form of the meso-and metaventra.

Subfamily, tribal and generic keys to the Ptiliidae of Sarawak
Sindosium collinsi sp.nov.urn:lsid:zoobank.org:act:E8C7E79C-4136-4C77-97DD-07373C1335D5Fig. 2 Diagnosis Shares with S. foveatum the pair of sulci under the mesoventral collar but distinguished from that species by the foveolate pronotum without a clearly defi ned medial fovea and by the shorter pubescence.From S. opacipenne it may be distinguished by the foveolate mesoventrum and from S. bacchusi by the form of the hind angles of the pronotum lacking semi-circular incursions.

Etymology
Named after Nicholas M. Collins, the collector of the paratypes and of other Sarawak specimens.COLOUR.Elytra dark brown, pronotum and head yellowish brown, antennae and legs yellow.Pronotum and elytra with pale pubescence the setae arising from small foveolae (Fig. 2D).
PRONOTUM.Length 0.24 mm width 0.41 mm, with wide lateral borders and raised serrate margins, posterior border with raised margin (Fig. 2D).
ELYTRA.Length 0.56 mm, width 0.48 mm, undersides of lateral margins with a single row of setae.
VENTRUM.Proventrum narrow in front of procoxae, with rows of foveae along the anterior and posterior margins, coxal cavities open behind (Fig. 2C).Mesoventrum, without reticulation or pubescence, collar sloping posteriorly for a short distance onto lateral margins, without distinct humeri, with a narrow raised medial ridge extending posteriorly to raised, rounded projection, not extending between the mesocoxae, posterior margin of keel with a pair of deep fringed sulci (Fig. 2E).Mesocoxae separated by almost half their width (Fig. 2E).Metaventrum with scattered pubescence and strongly raised anterior margin between mesocoxae, posterior margin forming a narrow bifi d projection between metacoxae, mesepiventral sutures apparent reaching posteriorly from mesocoxae to lateral margins.Wings of usual Sindosium type.FEMALE GENITALIA.Spermatheca (Fig. 2B).MALE GENITALIA.Not known.

Tribe Ptiliini Erichson, 1845
Genus Bambara Vuillet, 1911 Small, fragile and weakly sclerotised insects, widely distributed particularly in the tropics with many undescribed species.No published records from Sarawak.A careful study of the chaetotaxy of the head, legs, antennae, abdomen and other features failed to reveal the presence of any reliable differences to distinguish species.Similarly, no reliable features have been detected in the external skeleton.These fi ndings correlate with those of Dybas (1966) and Johnson (1971) both confi rming spermathecal differences as the best method of determining species.The use of elytral shape as used by the author in separating Madagascan Bambara has not proved to be helpful with these specimens, none of which possess elytra which are wider at, or close to, the humerus.No species were detected with a mesoventral collar extending onto the humeri as B. contorta Dybas, 1966 the only species in the genus recorded to date to exhibit this feature.
In dorsal view, species of Bambara are easily confused with some smaller, paler Acrotrichis and with species of Ptiliola, but are easily separated from the former by the longer elytra covering most of the abdomen and from the latter by the adjacent metacoxae separated only by the bifi d extension of the metaventrum.Dimorphism involving blindness and aptery, similar to that exhibited by species of Ptinelliini, has been shown to be present in the genus (Darby 2014b) but was not detected in the Sarawak species.

Diagnosis
Determined by the form of the spermatheca.

Etymology
Named after Peter Hammond, the collector of these specimens and of many other Sarawak species.

Diagnosis
Determined by the dark colouration and the form of the spermatheca which can only be confused with B. tortuosa sp.nov., but the 'corkscrew' in that species is longer and the coils arranged differently.

Etymology
Name recognises the close similarity of the spermatheca with that of B. tortuosa sp.nov.MALE GENITALIA.Aedeagus (Fig. 3G).

Remarks
The commonest species in the Gunung Mulu National Park.
Genus Dipentium Johnson, 1982 Genus of eleven species of robust, strongly chitinised beetles recorded from various tropical and subtropical parts of the world, especially in the Madagascan and Indo-Australian regions.The genus includes species with pronota that are both wider than and the same width basally as the elytra.The form of the mesoventral collar with a narrow medial ridge extending posteriorly from the raised front margin is shared with Greensladella Johnson, 2007, Micridium Motschulsky, 1869and Microptilium Matthews, 1872

Remarks
These specimens do show some slight differences from the D. latum specimens from Sabah in the medially less densely foveolate metaventrum and in the shorter mesoventrum but these are not considered suffi cient to designate them as a new species.
Genus Erro Darby, 2017 Genus of distinctive beetles erected to accommodate two species E. impiger Darby, 2017 andE. angolensis Darby, 2017 from Madagascar and Angola respectively.When describing the genus I declined to place it in a specifi c tribe simply stating that I considered it to be close to Discheramocephalini. (Darby 2017a).It is here placed in Ptiliini being the only suitable tribe available.

Diagnosis
Separated fom E. impiger and E. angolensis by the foveolate pronotum with acute hind angles.

Etymology
Named after James Brooke, the British explorer who became the fi rst Rajah of Sarawak in 1841 and whose descendants continued to govern the kingdom until 1946.HEAD.Antennomeres III-XI, length 0.34 mm.Width across eyes 0.26 mm.Head with a pair of foveolae on a level with the front of the eyes (Fig. 4C) and a longitudinal fossa behind the eyes.Mentum and submentum chaetotaxy (Fig. 4D).

Holotype
PRONOTUM.Strongly foveolate in posterior third the foveolate area extending forward into two shallow depressions either side of disc, lateral margins strongly sinuate before acute hind angles, median portion of hind margin projected slightly backwards, length 0.21 mm, width 0.33 mm.
ELYTRA.Pubescence arising from foveolae but no additional depressions as on the pronotum, widest about middle, hind margin slightly truncated.length 0.43 mm, width 0.43 mm.
VENTRUM.Mesoventrum coarsely reticulate medially and with sharply pointed teeth at the anterior angles, collar sinuate with a narrow medial ridge extending posteriorly to a sharply pointed keel between the contiguous mesocoxae, posterior margins sinuate (Fig. 4E).Metaventrum pubescent without evidence of epiventral sutures, metacoxae separated by ± ¼ the width of the sclerite.

Genus Ptiliola Haldeman, 1848
Genus of very small beetles with six recognised species from Europe and Angola, and numerous undescribed species from the tropics.The dorsal and ventral characters provide minimal help in the separation of species although the chaetotaxy of the metaventrum was found useful by Vorst (2007)

Additional material
Many other examples determined by association retained in alcohol.

Remarks
In 2018, I described Ptiliola semitaria from Angola and illustrated alongside the fi gure of the spermatheca a second fi gure of a spermatheca of a specimen with a reduced length of duct between the pump and chamber which I suggested might be P. semitaria (Darby 2018).The spermathecae of Ptiliola from Sarawak include examples of similar ducts ranging in length between the two seeming to confi rm that only one species is present.It is also worth noting that this form of spermatheca is similar to that of the European P. brevicollis (Matthews, 1860), but in that species the duct is shorter.
A fi gure of the spermatheca of the Sabah P. semitaria is included for reference (Fig. 5G) together with fi gures of the Sarawak insect (Fig. 5A-F).

Tribe Dis cheramocephalini Grebennikov, 2009
Genus Cissidium Motschulsky, 1855 Genus of worldwide distribution particularly in the tropical regions with numerous species, many awaiting description.(Ongoing research by the author proposes to designate several subgenera.)The new species described below share the following features: body convex, pubescent, head fi nely margined at sides, eyes of male larger and more prominent than those of the female, antennae long, antennomere XI constricted medially producing a 'dumbell' or 'hour-glass' like fi gure easily mistaken for two separate antennomeres.Pronota broader than long, sides curved sometimes angulate with clearly marked raised margins, posterior margin with insinuation opposite scutellum.Elytra entire, longer than broad, generally leaving ⅔ abdominal sclerites exposed.Prosternum very short anterior to procoxae which are contiguous.Mesosternum with a distinctive central keel reaching between the mesocoxae as a sharp point or wider, hind/side margin crenulate usually in posterior half, without clearly visible perforations [not withstanding that the tribe was erected to contain species with mesoventral perforations].Metaventrum slightly longer than the mesoventrum, metacoxae separated by ± ⅓ the width of the sclerite.Pygidium without teeth at apex.Dissections of the genitalia have not been attempted in some cases because external features are suffi cient to determine the species and the risk of destruction to the specimens.

Diagnosis
Id entifi ed by the globular appearance of the elytra and the shining dorsal surface frequently lacking pubescence.Might be confused with C. marshallae sp.nov.but that is a little smaller and more coarsely foveolate species.

Etymology
Refers to the rounded appearance of the elytra.HEAD.With a row of indistinctly formed foveolae on a level with the top of the eyes, antennomeres III-XI, length 0.25 mm, mentum and submentum with ± circular foveolae (not always clearly defi ned), wider anteriorly than posteriorly, anterior border rounded as Fig. 9C.
PRONOTUM.Length 0.19 mm, width 0.29 mm, foveolate throughout, two short carina at the base appearing only faintly or as a fusion of foveolae in some specimens, side margins angled medially, pubescence long, overlapping (but frequently abraded) (Fig. 7A).

Remarks
The pronotal sculpture is sometimes diffi cult to make out, side lighting is helpful.

Diagnosis
Identifi ed by the form of the mesoventrum which is unlike any other Sarawak Cissidium.

Etymology
Refers to the form of the keel and lateral margins of the mesoventrum.PRONOTUM.Length 0.19 mm, width 0.29 mm, foveolate throughout, foveolae forming short longitudinal depressions at base, side margins strongly sinuate, hind angles acute (Fig. 7B).
ELYTRA.Length 0.43 mm, width 0.37 mm, foveolate throughout, evenly rounded, broadest at middle.VENTRUM.Mesoventrum without pubescence, collar sharply angled posteriorly at humeri, angles projecting, lateral margins straight meeting posterior margin at rounded right angle, without serrations, keel fl at topped and parallel sided, widening and stopping short of the collar, tapering slightly between mesocoxae (Fig. 8D).Metaventrum with scattered pubescence, metacoxae separated by ⅓ width of the sclerite.

Remarks
The mesoventral characters suggest that this species belongs either to a subgenus of Cissidium or to a separate genus.

Diagnosis
The densely foveolate pronotum, the sinuate border of the anterior margins of the keel and the sharply pointed keel between the mesocoxae distinguish this species.

Diagnosis
The pronotal foveae distinguish this species from all others on Sarawak.From C. foveolatum Johnson, 1982 from New Zealand, which has similar large foveae on the pronotum, it may be distinguished by the more sinuate margins of the pronotum, the lack of a deep medial fovea on the forehead between the eyes and the wider keel between the mesocoxae.

Etymology
Refers to the large foveae on the pronotum.PRONOTUM.Length 0.22 mm, width 0.32 mm, with scattered pubescence and a row of foveae along the posterior margin, the four medial ones tending to form two large ones, side margins sinuate before the acute hind angles (Fig. 7E).

Diagnosis
The triangular shape of the mentum distinguishes this species from all others.
VENTRUM.Mesoventrum without pubescence, collar extending onto humeri without a terminal tooth, lateral margins almost straight before turning to meet mesocoxae, keel becoming rugose before narrowing to a point between the mesocoxae (Fig. 8F).Metaventrum with scattered pubescence throughout, posterior margin between metacoxae with two sharp points at corners, metacoxae separated by ¼ width of the sclerite.

Remarks
The form of the mentum and the mesoventral characters suggest that this species belongs either to a subgenus of Cissidium or to a separate genus.

Cissidium spp.
Several other species of Cissidium were also present in the material as fragments, one with a foveate head (Fig. 9D), another with ringed pronotal foveolae (Fig. 9C).These have not been considered complete enough to be described as new or determined as existing species.
Genus Discheramocephalus Johnson, 2007 Fifteen species have been described to date from Madagascar, Peru, Solomon Islands, Indonesia and Africa, and Johnson stated that he had also seen specimens from Brazil and Sri Lanka (Johnson 2007).

Diagnosis
Easily distinguished from all other Ptiliidae in Sarawak by the longitudinal foveae on the pronotum, and by the pair of deep sulci on abdominal ventrite VIII (most easily seen in dissections but not showing in Fig. 10F).

Etymology
Named after the Latin adjective 'niger', meaning 'dark', and referring to the insect's colouration.HEAD.With a deep transverse fossa behind the eyes extending laterally to the ventral surface and a group of setae in clearly defi ned foveae behind each eye (Fig. 10D).Antennomeres III-XI, length 0.21 mm.Distance across eyes 0.17 mm.PRONOTUM.Length 0.12 mm, width 0.19 mm, with a pair of longitudinal foveae on the disk and another pair close to the lateral margins, in between these two much smaller foveae close to the posterior margin on each side (Fig. 10B).Scutellum with a sharp central keel (Fig. 10E).

Holotype
ELYTRA.Length 0.33 mm, width 0.27 mm.VENTRUM.Proventrum depressed in front of procoxae and with raised angular humeri, extending posteriorly.Mesoventrum with a broad strongly reticulated medial keel and concave lateral margins before posterior termination, keels present extending to sides of mesocoxae, mesocoxae separated by their width, posterior margins obliterated.Metaventrum with scattered pubescence, anterior margins extending in form of a lobe between the mesocoxae, metacoxae almost adjacent.
ABDOMEN.Depressed laterally apparently for reception of metatibiae and tarsi, fi rst visible segment with a serrated posterior margin, ventrite VIII with a pair of deep sulci.Pygidium with ± 10 spines and two coarse setae near the anterior corners (Fig. 10F).Wings of usual ptiliid type.Dissection failed to reveal any genitalia to determine sex, but size of eyes suggests male (females in this genus usually have smaller eyes).
Tribe Nanosellini Barber, 1924 Genus Kuschelidium Johnson, 1982 Described by Johnson on the basis of a single specimen K. maori Johnson, 1982 from New Zealand.The rounded body form and possession of a spatulate plate covering the mesocoxae, are similar features to those possessed by members of the termitophilous subfamily Cephaloplectinae, but in those species the plate is an extension of the proventrum and not of the mesoventrum (incorrectly referred to as the metaventrum by Sawada & Hirowatari 2002).In describing the genus Johnson (1982) refrained from placing it fi rmly in a subfamily suggesting that the almost contiguous metacoxae and entire elytra placed it closest to some of the nanoselline genera including Mikado Matthews, 1889 and Throscidium Matthews, 1872.Sawada & Hirowatari agreed when describing K. okinawense Sawada & Hirowatari, 2002 from Japan and this is followed here, although the very clear morphological differences between the genus and most other genera in the tribe may well see it change in the future.HEAD.Head and antennal insertions concealed beneath pronotum in dorsal view but eyes visible; distance across eyes 0.29 mm, antennal grooves present (Fig. 11B).Mentum very contracted length 0.03 mm, width 0.06 mm, without prominent setae in the anterior corners and with a wide anterior margin; submentum with two setae only (Fig. 11B).Labrum densely pubescent.Antennomeres III-VIII length 0.13 mm, antennomere V slightly longer than IV and VI, antennomeres IX-XI length 0.12 mm forming a loosely jointed club.PRONOTUM.Strongly domed, anterior margin with projecting corners to acco mmodate eyes, posterior margin sinuate the medial portion shallowly concave and the corners acutely angled.Prosternum almost absent in front of procoxae.Mesosternum with a large spatulate plate of length 0.22 mm, width 0.25 mm, covering the pro-and mesocoxae and extending over half of the metaventrum, the hind margin with an incursion to allow for the raised medial portion of the metasternum (Fig. 11D).

Remarks
Placed in Kuschelidium on grounds of priority.The size of the mesoventral spatulate plate which is much larger than that of any described species of Kuschelidium begs the question as to whether the new species belongs in a different genus.I have seen an undescribed species from Tioman, Malaysia, with a similar plate of smaller size but larger than K. maori and given the presence of this possibly transitional species, it seems safer to assign the new species to Kuschelidium until more specimens have been found to provide a better basis for analysis.Although the specimen was not found in association with termites its peculiar morphological modifi cations do suggest a life adapted for the hostile environment of the termites' nest.

Etymology
The name is an anagram of the genus name Ptinella.

Description
Body shallowly convex, rather broad, with clear reticulation, densely foveolate and pubescent, the pubescence, barely overlapping, longer along the lateral margins.Head broad, with a row of pustulate setae behind the eyes; mentum with sharply pointed anterior angles, the two longer anterior setae set behind two shorter setae, disc with two rows of two setae, reticulation sharply marked, submentum with four prominent setae at lateral margins; antennae 11 segmented, antennomeres XI-XI forming a loosely jointed club.Pronotum with two depressions marked by coarser reticulation, sides evenly rounded to obtuse posterior angles, lateral and posterior margins with a fi ne raised border, scutellum triangular sharply pointed.Metascutellum without lateral setae.Elytra evenly rounded, without epipleura, setae arising from concave border of cells.Proventrum, reticulate, broad in front of contiguous procoxae, with a ridged anterior border and row of short setae, coxal cavities closed behind.Mesoventrum reticulate, without pubescence, collar not extending onto the humeri which are sharply toothed, lateral and posterior margins evenly rounded, keel rounded anteriorly not reaching collar, fl at topped and 'teardrop' shaped, extending to a point between the mesocoxae.Metaventrum reticulate and pubescent, posterior margin between metacoxae broad, half the width of the sclerite, without lateral points, metepisternal sutures absent.Pygidium with a small medial point.Female spermatheca very small, globular.Male aedeagus arcuate with a short projection at the anterior end.

Remarks
The form of the mesoventral keel distinguishes this genus from all others in the Ptinellini.(Darby, unpublished).Throscidium species have a similarly shaped keel, but the sharply defi ned semi-circular lateral margins of the mesoventrum of that genus are entirely different.

Diagnosis
Determined by the form of the mesoventral keel.

Etymology
From the Latin 'gutta', meaning 'drop', and referring to the shape of the mesoventral keel.

Genus Ptinella Motschulsky, 1844
Widespread genus of small and fragile species associated with saproxylic habitats.Dimorphism is a common feature, the dominant form (aptera) being characterised by being depigmented, blind or with reduced eyes and apterous.Normal individuals (alata) are usually more pigmented, often have less truncate elytra and possess eyes and wings.
Ptinella alisonae sp.nov.urn:lsid:zoobank.org:act:4BDD6A5D-9D57-4879-98CD-670F69CF33E5Fig. 13 Diagnosis Separated from all other Ptinella spp.by the form of the spermatheca and the presence of the projecting setae on the pronotum.Differs from the indeterminate species below in lacking sinuate hind angles to the pronotum.

Etymology
Named after Miss Alison Michie, a lifelong family friend and fond of botanical knowledge.HEAD.Without a transverse fossa behind and with no obvious reticulation, antennomeres III-XI, length 0.25 mm.distance across eyes 0.20 mm, mentum and submentum chaetotaxy (Fig. 13D).

Holotype
PRONOTUM.Almost as wide as the elytral base, without obvious reticulation, lateral margins with three projecting setae and without a sinuation before the hind angles, posterior margin slightly sinuate the central portion projecting posteriad, length 0.13 mm, width 0.23 mm (Fig. 13E).

Ptinella sp.
Several examples of a second species of Ptinella are present in the material but no spermathecae were found in the dissections and consequently they have not been determinable for the reasons given above.Subfamily Acrotrichinae, Reitter, 1909Tribe Nephanini Portevin, 1929 Genus Baeocrara Thomson, 1859 Seven species of Baeocrara have been described from Europe, Japan, India, Sri Lanka, Nepal, Philippines, Zaire (Johnson 1988) and Sabah (Darby 2019).

Remarks
The distinctive mesoventral collar (Fig. 17B) separates the species from all other genera in the tribe, and the form of the aedeagus from all other species in the genus.Baeocrara minima has also been recorded from Sabah.The Sabah specimens are slightly larger than the Sarawak specimen, but apparently possess no other features to merit description of the latter as a new species.

Tribe Acrotrichini Reitter, 1909
Genus Acrotrichis Motschulsky, 1848 The largest ptiliid genus, distributed worldwide, with numerous described species.Unless stated otherwise, all spe cies share the following features: body elongate, usually rather broad, relatively fl at, dorsal surface including the head pubescent.Antennae with 11 antennomeres I-II forming the scape and pedicel being much larger than III-XI, and IX-XI forming a loosely formed and tapering club; all antennomeres bearing long setae.Sides of pronotum with a narrow raised margin, and hind angles produced backwards.Scutellum without distinguishing features.Metascutellum with a single lateral spine or spur on each side (not present in any other Ptiliidae subfamily (Hall 2000).Elytra truncate apically exposing ± four abdominal segments.Proventrum narrow in front of the procoxae.Mesoventrum with a well-developed collar extending across the pleura and a raised keel between the mesocoxae.Metasternum pubescent, posterior margin between the metacoxae with sharp lateral points.Metacoxae with rounded plates tapering towards the lateral margins.Abdominal tergites II-V with wing folding spicule patches.Pygidium composed of tergites IX and X fused seamlessly together with or without ⅔ teeth.Abdominal ventrite I without femoral lines.Male ventrite VI with a more or less curved excision, ventrite VII small, covering the excision in ventrite VI, and with an anteriorly directed apodeme.Aedeagus symmetrical in dorsal/ventral view often, but not always, with two hooks.Spermatheca well developed.Wings of usual featherwing type.Parthenogenetic species have been recorded.
Several attempts have been made to establish subgenera and, more recently, species groups within specifi c geographic faunas.However, the validity of some of these classifi cations is questionable if a more holistic view is taken and allowance made for new criteria resulting both from the discovery of many new species and also from better descriptions of old ones.For this reason and until the genus is better understood, no attempt is made here to assign species to particular groups and they are treated instead in one alphabetic sequence.Further information together with a more detailed account of the morphological features useful in separating species of Acrotrichis is included in Darby (2014a).

Diagnosis
The acute angles of the pronotum and form of the spermatheca distinguish this species.

Etymology
Refers to the sharp corners of the pronotum.

Remarks
Previously known only from Sabah.The form of the spermatheca distinguishes the species (Fig. 17C).

Diagnosis
The fl attened hind angles o f the pronotum together with the form of the genitalia distinguish this species.

Diagnosis
The short metaventral termination and form of the genitalia distinguish this species.

Etymology
Named after the form of the metaventral termination between the metacoxae.
PRONOTUM.Length 0.22 mm, width 0.47 mm, hind angles with a tiny sinuation in the lateral margin creating an acute angle (viewed from 45°).

Remarks
The close proximity of the metacoxae makes this a marginal choice for placement in Storicricha (see below).Johnson, 1969 Fig.

Diagnosis
The form of the spermatheca distinguishes this species (Fig. 17A).

Remarks
Tropical, mainly synanthropic species recorded from various parts of tropical Asia.Johnson (1985) noted that he had seen only females from the Seychelles and Mascarenes and considered that the species was parthenogenetic; he added the rider, however, that he had also seen possible males from West Bengal.More recently, he determined males taken by myself in Kerala, S. India, in association with females as possibly britteni (unpublished).

Remarks
Previously only known from Sabah.

Diagnosis
The microtrichiate elytra (Fig. 17D) and the shape of the spermatheca distinguish this species.The elytral microtrichiae give the elytra a dull appearance rather than the blue-grey iridescent sheen of Nearctic and Palaearctic specimens which I have seen tempting a determination as the very similar, both morphologically and in the form of the spermatheca, with the equally widespread A. josephi Matthews, 1872.

Remarks
Adventive, synanthropic, parthenogenetic species recorded from North America and New Zealand.

Diagnosis
The long row of setae on the male abdominal ventrite VI distinguishes it (Fig. 17B).

Remarks
Widespread and common tropical to temperate, mainly synanthropic species but also occurring in natural habitats.

Diagnosis
Only likely to be confused with A. belli sp.nov., but the longer and narrower body and form of the genitalia distinguish it.

Etymology
Named after Michael Geiser, my colleague in the Department of Life Sciences NHM.

Diagnosis
The rounded body form, possession of elytra with wide epipleura and a medial foveola in the mesoventral collar distinguish this species.

Diagnosis
The large size, wide separation of the metacoxae and form of the genitalia distinguish this species.

Etymology
From the Latin 'plaga', meaning 'trap', and referring to the similarity of the spermatheca to a plumber's trap.
Genus Storicricha Johnson, 1988 In describing this genus, which was based on two species from Sri Lanka, Johnson (1988) noted that there were no features distinguishing it from Acrotrichis except for the approximate metacoxae separated only by a narrow bifurcate extension of the metaventrum.Future research on the subgenera of Acrotrichis (in progress) may reduce the status of Storicricha to that level.Four additional species have been added to the genus recently from Peru (Darby 2017b).

Diagnosis
The bifi d termination of the metaventrum and form of the spermatheca distinguish this species.

Discussion
These collections involved ± 1900 specimens of 20 species in 19 genera trapped in fi sh baited pitfalls and 110 specimens of 18 species in 8 genera collected from litter samples.Of the pitfall trapped specimens, the vast majority, ± 1640, are in the genera Acrotrichis, Storicricha, Bambara and Ptiliola.It is interesting to note that the morphological differences between the species of Acrotrichis and Storicricha in particular, compared with those of the same genera in other regions, appear to be much less pronounced.The wide range of pygidial, elytral, abdominal and other features recorded in Nearctic species is not present in the specimens from both Sarawak and Sabah most of which are smaller and paler.Furthermore, their overall similarity to species of Ptiliola, and Bambara is such that a careful microscopic study is required to separate them.As a result, many have been determined on the basis of association and not designated as paratypes.The few examples of adventive species such as A. cursitans and A. cognata however immediately stand out as being clearly alien to the fauna.
The six new species of Cissidium add further evidence to this being a highly speciose genus throughout the tropical regions in contrast to Ptenidium, which is speciose in regions to the north and west, and has also been recorded from neotropical countries, which might have been expected to occur in the material, but no specimens have been found from either Sarawak or Sabah.

Fig. 1 .
Fig. 1.Map of Sarawak showing location of the Gunung Mulu National Park where the Ptiliidae were collected.

FEMALE
GENITALIA.Spermatheca robust with part of the coils in the form of a corkscrew (Fig.3Ea-Eb).

alluvial forest litter; BMNH.
in the Ptiliini, but they are much smaller and less robust species.
in distinguishing the European species P. fl ammiferaMlynarski, 1985.