Porcelloderes impenetrabilis gen. & sp. n. from Tanzania, an Assassin Bug Camouflaging in the Adult Stage (Hemiptera: Heteroptera: Reduviidae: Physoderinae)

ABSTRACT Porcelloderes impenetrabilis gen. & sp. n. (Hemiptera: Heteroptera: Reduviidae: Physoderinae) is described, based on males, females, and larvae from different localities in northeastern Tanzania. The new discovery extends the range of the subfamily (previously known from the Oriental Region and the Pacific, from Madagascar and neighbouring islands, and from Central and South America) to mainland Africa. In contrast to all previously described physoderine species, the new species is apterous, which is probably a result of neoteny; the neotenous aptery and its morphological consequences are discussed. The diagnosis of Physoderinae is extended in order to make it applicable to apterous taxa. In all examined specimens including larvae, the body surface is covered by a firm incrustation of soil, deposited between the long setigerous tubercles. This is the first record in the subfamily Physoderinae of camouflaging by application of material on the body, and the first report of such behaviour in the adult stage in Reduviidae.


INTRODUCTION
Physoderinae is a small subfamily within Reduviidae, which has an unusual geo graphic distribution. The largely unrevised Physoderes Westwood, 1846 occurs wide ly in the Oriental Region and the Pacific, with nearly 40 described species. Eleven small ge nera, each containing one to six (altogether 26) species, are distributed in Ma dagascar, Mauritius and the Comores; these were monographed by Villiers (1968). Two mo notypic genera, Cryptophysoderes Maldonado Capriles, 1972 andLeptophysoderes Weirauch, 2006, have been described from the New World: Panama and Ecuador, respectively. Of the two New World genera, Cryptophysoderes is rather similar to the Old World forms; however, Leptophysoderes shows several unique characters. No species have been known to occur on the mainland of Africa so far (Maldonado Cap riles 1990;Weirauch 2006a).
Among material collected in Tanzania, a series of a physoderine assassin bug re presenting a previously unknown genus and species were found and the bug is described in the present paper. This discovery represents the first record of the subfamily from the African continent.

MATERIAL AND METHODS
All examined specimens of the new species are in the collection of the Hungarian Natural History Museum, Budapest. For this study, all described Old World genera of Physoderinae have been examined (the Malgasy genera were accessed in the Mu séum National d'Histoire Naturelle, Paris). The New World genera were thoroughly documented and illustrated by their authors (Wygodzinsky & Maldonado Capriles 1972;Weirauch 2006a). Therefore, it was not necessary to re-examine them directly.
In order to study the external morphology, specimens of the new species had to be cleaned. The solid soil incrustation covering the body turned out to be impossible to remove by using forceps or pins, even from specimens transferred to detergents. Consequently, a male and a female adult (paratypes) as well as a last instar larva were placed in alcohol and cleaned by ultrasonic cleaner at the Institute of Chemistry, Eötvös Loránd University, Budapest. Only from these three cleaned specimens was it possible to take exact measurements, which are given in millimetres.
External and genital structures were examined using a stereoscopic microscope (MBS-10) and uncleared and cleared alcohol-glycerol mounts were studied under a compound microscope (XSZ-N107), partly by oil immersion (Fig. 22). All drawings were made using a camera lucida. Measurements were taken using a micrometer eyepiece. Male genitalia were studied after brief maceration in potassium hydroxide solution. TAXONOMY Genus Porcelloderes gen. n.
Etymology: From Latin porcellus (piglet) and Greek deire (neck), the latter referring to Physoderes, the type genus of Physoderinae. Gender feminine. Type species: Porcelloderes impenetrabilis sp. n. Diagnosis: Recognized within Physoderinae by the combination of the following characters: body small, about 4.5-5.0 mm; apterous; body covered by wide, stiff, curved hairs arising from prominent, wart-like tubercles (Figs 5, 6), markedly affecting outlines of head and pronotum (Figs 7-10); ocelli absent; antennal segment I not reaching apex of clypeus ( Fig. 9); pronotum transversal, its main body is formed by the anterior lobe, the posterior lobe is reduced to a narrow transverse rim, posterior margin without submedian lobes (Fig. 10); mesoscutellum not differentiated; tarsi two-segmented . Description: Body: Small apterous physoderines, length of adults about 4.5-5.0 mm. Body broad, robust (Figs 1-3); body surface covered by wide, stiff, curved hairs set on long, wartlike tubercles (Figs 5,6); abdominal venter covered with short, adpressed hairs. Head ( Fig. 7): Elongate, porrect, densely covered by very long and dense setigerous tu bercles; anterior and posterior lobes separated by a deep transverse impression dorsally at level of eyes; preocular part about twice as long as postocular part; eye ( Fig. 9) very small, globular, strongly protruding in dorsal view, far removed from dorsal and ventral outline of head in lateral view (Fig. 7); antennae situated approximately halfway between apex of clypeus and anterior margin of eye. Antenna (Fig. 9) as usual in subfamily, short, apex of segment I not reaching apex of clypeus. Labium (Fig. 7) as usual in subfamily, long and slender, apparent first segment (II) relatively short, stout, not reaching to level of antenniferous tubercle, apparent second segment (III) very long and slender, narrowing posteriorly, apparent third segment (IV) shortest.
Thorax: Pronotum ( Fig. 11) transversal, its main body formed by anterior lobe, posterior lobe reduced to narrow transverse rim along its posterior margin; anterior margin forming broad, flattened collar, anterolateral angles obtuse; distinctly marginated laterally, lateral margin with row of almost regularly arranged long setigerous tubercles; disc with more or less longitudinal rows of long setigerous tubercles. Mesonotum and metanotum short, transverse, with fairly long setigerous tubercles laterally, posterior margins thickened, forming transverse carinae. Pro-and mesonotum each with rather deep medial impression at their base; mesoscutellum not differentiated; metanotum impressed medially. Thoracic pleuron covered with sparse, fairly long setigerous tubercles. Meso-and metathoracic wings entirely absent. Legs (Figs 11-14) short and stout; coxae very short; trochanters long as characteristic in subfamily; all femora widened, with their ventral surface un armed except for setigerous tubercles; tibiae simple, stout; femora and tibiae with re gular longitudinal rows of small setigerous tubercles; tarsi two-segmented, segment I very small.

Figs 1-29
Etymology: From Latin impenetrabilis (impenetrable), referring to the firm soil layer covering the body of all specimens examined.

Description:
Apterous male and female. Colour: General body colour rather uniformly dark brown, head somewhat lighter. Antennal segment I light yellowish brown, segments II-III same colour as head, apical half of segment IV stramineous. Labial segment I and base of segment II light yellowish brown, apical 2/7 of segment II and entire segment III dark brown. Leg colouration the same as overall body colour, base of tibiae and apical tarsal segment light brown.
Male genitalia: Genital capsule as in Figs 16, 17, short, oval, dorso-apical part with short, stout, apically rounded process (Fig. 18). Paramere (Figs 19-21) short, apical half relatively narrow, angularly bent around middle, apical half thick, nearly straight, apically truncate, external margin with a series of tubercles, each having hair sensilla apically (Fig. 22). Articulatory apparatus of phallus (Figs 23, 24) stout, support bridge complex with narrow ponticulus transversalis, with 2+2 capitate processes, basal foramen transverse, oval, with thick ductifer; support bridge complex continued in 1+1 relatively short and thick support bridge prolongations fused along their whole length; phallotheca short and broad, oval, with tongue-shaped dorsal sclerotized plate (Figs 23, 24: dsp) and 1+1 broad, nearly triangular, ventral sclerotized plates ( Fig. 23: vsp); endosoma with several minute, tooth-like sclerotized processes forming distinct fields; struts fused, spoon-shaped in dorsal view ( Fig. 24: str), apical portion fused with dorsal sclerotized plate of phallotheca.  relatively strongly sclerotized, abdomen greatly membranous. Head (Fig. 8): Similar to that of adult, about 1.55 times longer across eyes than its width, preocular part about 2.15 times longer than postocular part; head across eyes about 1.2 times wider than interocular distance; eyes small, weakly protruding laterally. Thorax: Pronotum about 1.4 times longer than its greatest width, lateral margin broadly rounded, posterior margin projecting posteriorly along midline; meso-and metanota weakly sclerotized, short, incompletely separated from each other, their lateral margins rounded. Legs: Short and stout, similar  Habitat and biology: The specimens examined during the present study were collected in February 1987 from four localities in north-eastern Tanzania; the longest distance between two localities is approximately 250 km. Additional data on the localities were provided by Mahunka et al. (1987). Specimens from Matombo were extracted with a Moczarsky-Winkler bag from material sifted from accumulated debris near the entrance of a cave. Specimens from Kimboza Forest Reserve were captured on the same day from a locality of a few kilometres away from the previous one, at about 250-300 m a.s.l.; they were extracted with Berlese funnel from litter taken in the gallery forest surrounding the river Ruvu. Specimens from Kwamgumi were extracted about two weeks later with Berlese funnel from litter and soil collected in a primary rainforest in Segoma Forest Reserve. According to Mahunka et al. (1987), specimens from Amani were collected at light, which statement might be erroneous. However, specimens of several apterous hemipterans are known to approach light sources by walking. There was yellow, orange or red lateritic soil in all the localities.

DISCUSSION
Neotenous aptery in Porcelloderes gen. n. All described members of Physoderinae are macropterous, brachypterous specimens probably representing an undescribed species of Physoderes have been deposited in some collections (W.S. Hwang pers. comm.); however, no apterous specimens have been known so far. Furthermore, no species exhibiting pterygopolymorphism (i.e., the occurrence of more than one alary morph) has been reported. Although the new species is therefore an unusual member of the group, its subfamily assignment is with certainty based on the following characters: body surface with setigerous tubercles; labium straight, with apparent first and third segments short and apparent second segment longest (Fig. 7); trochanters long and proximally narrow (Figs 12-14); fossula spongiosa absent in all legs; and fore tibial comb set on a prominent spur (Figs 11, 12).
Porcelloderes impenetrabilis gen. & sp. n. is apparently a paedomorphic species: its peculiar morphology is a result of heterochronic changes in its ontogeny. Of the eight modes of heterochrony (Alberch et al. 1979), the new species probably exhibits neoteny, viz., paedomorphosis resulting from general slowing down of developmental rates in shape. In neotenously apterous adults, wings are completely missing, and a number of larval characters are retained in the adult stage. Such morphs occur in several groups of Heteroptera, at least in Enicocephalidae, various families of Gerromorpha, Aradidae, Termitaphididae, Blissidae, and Coreidae: Agriopocorinae. Among Reduviidae, this phe nomenon is especially common, and occurs in at least the following subfamilies: Eme sinae, Saicinae, Tribelocephalinae, Ectrichodiinae, Stenopodainae, Reduviinae, Sal yavatinae, and Harpactorinae: Rhapidosomatini.

Diagnostic characters and relationships of Porcelloderes gen. n.
Many unique characters of Porcelloderes are consequences of neoteny, most importantly the absence of ocelli, the features connected with the strong modification of the whole thorax (posterior lobe of pronotum strongly reduced, no articulating wings present, mesoscutellum not differentiated), and the two-segmented tarsi. Since no ana lysis of the evolutionary relationships within Physoderinae exist, no other apterous member of the subfamily is known, and many unique characters of P. impenetrabilis sp. n. obviously resulted from neoteny, it is difficult to speculate about the phylogenetic relationships of the new genus. The most important characters to consider are the following. Two-segmented tarsi. -Within Reduviidae, as in the whole Cimicomorpha, the oc currence of three-segmented tarsi is a plesiomorphic condition. This character is shared by most genera of Physoderinae. Two-segmented tarsi, found in Porcelloderes, is shared only by the following physoderine genera: Physoderoides Miller, 1955, Rodepirea Villiers, 1972, and the two New World genera, Cryptophysoderes and Leptophysoderes. The two-segmented condition probably evolved independently more than once in Physoderinae. This character is difficult to evaluate since its occurrence in P. impenetrabilis sp. n. is apparently a larval feature retained in the adult stage. However, I am not aware of any genus within Heteroptera in which apterous species bearing two-segmented tarsi and macropterous species bearing threesegmented tarsi are accommodated. Short antennal segment I. -The length of antennal segment I was considered by Villiers (1968) as being of generic importance within Physoderinae. The following genera have a short antennal segment I, not reaching the apex of the clypeus: Paulianocoris Villiers, 1953, Epiroderoides Villiers, 1962, Befotaka Villiers, 1962, Henicocephalo ides Villiers, 1962, and Maroantsetrana Villiers, 1968  -Several of the physoderine genera have a rough, granulose or finely tuberculate integument; however, no species are known to have similar large and long tubercles that markedly affect the outlines of the head and pronotum.
In conclusion, since it is impossible to positively place the new species into any of the existing genera, and also taking into consideration that no members of the subfamily have hitherto been reported from the mainland of Africa, the establishment of a new genus to accommodate the new species is justified. The phylogenetic relationships of Porcelloderes gen. n. remain unknown.

Extended diagnosis of Physoderinae
Weirauch (2006a) critically revised the original definition of Physoderinae (Miller 1954). However, since only macropterous morphs have been known up until now, some cha racters in her revised diagnosis apply only to these. The diagnosis of Physoderinae is accordingly supplemented with the following: In apterous morphs, ocelli absent; thorax strongly modified as follows: pronotum short, transverse, its main body is formed by the anterior lobe, posterior lobe is reduced to a narrow transverse rim along its posterior margin, which is without paramedian lobes; mesonotum very short, transverse, mesoscutellum not differentiated; metanotum very short; meso-and metathoracic wings entirely absent.
Very few field observations exist on physoderines. Most species are cryptic, and spe cimens have been found mainly among vegetable debris, the bases of banana and Pandanus leaves, in the staminate strobilus of Cycas, in hollow trees, and in caves (Usinger 1946;Miller 1954;Wygodzinsky & Usinger 1960;Wygodzinsky & Maldonado Capriles 1972;Schuh & Slater 1995). Specimens have sometimes been collected from plants by insecticidal fogging (Weirauch 2006a), from traps baited with human faeces, or while feeding on dipteran larvae (Martínez & Carcavallo 1989). The single report of the Neotropical Cryptophysoderes fairchildi feeding on vertebrate blood (Carvacallo & Tonn 1976) needs confirmation.
All examined adults and larvae of P. impenetrabilis sp. n. collected in various loca lities were uniformly covered by a thick and firm layer of soil. Camouflaging in Re duviidae by application of material on the body was reviewed by Cai et al. (2002) and Weirauch (2006b). Such behaviour is known for larvae of certain genera of the sub families Reduviinae, Cetherinae, Salyavatinae, Stenopodainae, Triatominae, and Sphae ridopinae. Although museum specimens of physoderines more or less covered by dirt are not rare (W.S. Hwang pers. comm.), no specimens with what approaches the firm mud layer on Porcelloderes have been reported. Camouflaging by application of material on the body has never been documented in this subfamily; the present observation on ca mouflaging in P. impenetrabilis sp. n. is the first record of such behaviour in the subfamily Physoderinae, and also in adult Reduviidae.
In the camouflaging of reduviid larvae, two different kinds of structures facilitate attachment of the camouflaging particles to the body surface: the anchor setae hold the material mechanically, whilst the trichomes, which are composed of glandular units and hair-like projections, fix the particles with the sticky secretion of the glands. These structures were documented in detail by Weirauch (2006b) in various species belonging to several subfamilies. A larva of P. impenetrabilis sp. n. was carefully macerated, and both surfaces of the integument of the abdomen were carefully examined under a microscope, but no glandular units could be detected. However, the fact that the soil particles on the body are firmly cemented together and difficult to remove mechanically even if the specimen is soaked in water, alcohol, moisturizers or detergents, makes it highly possible that the soil particles are glued together by a sticky secretion of unknown origin.
In adults of P. impenetrabilis, both the dorsal and the ventral surfaces of the abdomen are ornamented with highly elevated carinae (Figs 2, 15). The anterior, lateral and pos terior margins of syntergite I-III, the fusion lines between mediotergites I-II and II-III, the posterior and lateral margins of mediotergites IV-VI, the lateral margins of mediotergite VII, the posteromedian angles of epipleurites II-VI, and the posterior margins of all visible abdominal sternites are conspicuously elevated, and ornamented with setigerous tubercles. Areas surrounded by setigerous tubercles on the head, pronotum and abdomen are smooth. The camouflaging material (soil) is certainly deposited in these deep, smooth areas surrounded by tubercles, and fixed mechanically partly by the high tubercles themselves and partly by their serrate apical setae. The abdomen of the larva is weakly sclerotized and lacks such conspicuous carinae; as a consequence, the mud layer on larvae is thinner and concentrated mainly on the head and pronotum.
In some reduviid genera, species that exhibit camouflaging behaviour possess a fan of long setae. It is situated at the apex of the apical tarsal segment of the hind leg, and is responsible for gathering and loading camouflaging material on to the body. A tarsal fan such as this is absent in other genera (Weirauch 2006b). No similar application structures were found on the tarsi of any of the adults and larvae of P. impenetrabilis sp. n. In this species, the method of application of the camouflaging material on to the body remains unclear.