Phasmatidae Gray, 1835

Hennemann, Frank H. & Conle, Oskar V., 2008, Revision of Oriental Phasmatodea: The tribe Pharnaciini Günther, 1953, including the description of the world's longest insect, and a survey of the family Phasmatidae Gray, 1835 with keys to the subfamilies and tribes (Phasmatodea: " Anareolatae ": Phasmatidae), Zootaxa 1906, pp. 1-316 : 17-20

Phasmatidae Gray, 1835 sensu stricto

Type genus: Phasma Lichtenstein, 1796: 77 .

Phasmidae Gray, 1835: 12 .

Phasmidae Karny, 1923: 235 .

Günther, 1953: 546.

Phasmatidae, Bradley & Galil, 1977: 186 . [Corrected spelling of Phasmidae Karny, 1923: 235 ]

Otte & Brock, 2005: 31.

Lanceocercata Bradler, 2001: 179. syn. nov.

Sensu Bradley & Galil (1977: 180) the family Phasmatidae Gray, 1835 contained six distinct subfamilies, five of them distributed througout the Old World ( Phasmatinae , Tropidoderinae , Xeroderinae , Platycraninae and Eurycanthinae ) and one, the Cladomorphinae , inhabiting the Neotropical Region. Close relationship between the latter and the five Old World subfamilies is rather unlikely (→ 4.1). Apparently, the Phasmatidae as interpreted by Bradly & Galil (1977) form an artificial group, which is not only seen in containing a single not closely related Neotropical taxon, but also in several morphological features of the exosceleton of the insects such as the genitalia, structure of the profemora or antennae.

Based on morphological examination of the genital exosceleton and copulation habits Bradler (2001) recognized a predominantly Australian and supposedly monophyletic group of anareolate phasmatodeans he termed Lanceocercata. Subsequent, cladistic studies ( Tilgner, 2002) and molecular studies (Whiting et al., 2003) support the monophyly of this group. Bradler (2001: 183) interpreted the rather basal ground pattern of Lanceocercata, like the just slightly prognathous head, presence of ocelli, short thorax and long tegmina, as an indication that this group must have splitted off rather early from the remaing Phasmatodea . According to Bradler (2001: 183), Lanceocercata includes the subfamilies Tropidoderinae and Xeroderinae , sections of Phasmatinae (tribes Phasmatini and Acanthoxylini ) and Pachymorphinae (tribe Pachymorphini ), as well as the subfamily Platycraninae , except its type genus Platycrana Gray, 1835 . Consequently, large traditional groups like the subfamilies Phasmatinae , Pachymorphinae and Platycraninae are currently believed to be polyphyletic ( Bradler, 2001 & 2003).

Bradler (2001) based the monophyly of Lanceocercata on the following five supposedly apomorphic characters:

1. Cerci strongly laterally flattened and ± enlarged, foliaceous or lanceolate.

2. Vomer of ♂♂ strongly reduced and concealed by sternum XI (= paraproct). Functionally replaced by a clasping apparatus of the anal segment (= tergite X).

3. Anal segment (= tergum X) of ♂♂ specialized and forming a clasping apparatus to hold fast to the ♀ abdomen during copulation. Tergite strongly tectiform, longitudinally split and forming two flexible semi-tergites, only connected by a thin membrane dorsally. Interior surfaces of anal semi-tergites posteroventrally armed with a variable number of distinct incurving teeth (= “Dornenfeld”).

4. Subgenital plate of ♀♀ (= sternum VIII) with a prominent, ± ledge-like longitudinal keel in basal portion.

5. Derived copulation position. By making use of the clasping apparatus of their anal segment ♂♂ grasp the ♀ along the longitudinal keel of the subgenital plate (= sternum VIII).

Detailed examination and extensive comparison of genital structures and other morphological characters (e.g. structure of the profemora and antennae) or copulation habits here undertaken amongst the concerned taxa and other related subgroups, support a monophyly of Lanceocercata. Certain subfamilies included in the Lanceocercata by Bradler (e.g. Xeroderinae and Pachymorphini ) however are rather insufficiently defined and most certainly artificial groups, which clearly warrant better recognition (→ 4.6). This is in particular indicated by containing very differently structured types of genitalia, some of which do not at all match with the characteristics listed by Bradler. Indeed however, the five supposedly apomorphic features that Bradler (2001) listed to characterize Lanceocercata are true for almost all of the taxa originally included, and apparently such correlating specialisations are rather unlikely to have been evolved independently in separate subgroups, thus supporting Bradler’s hypothesis. The concerned features and their importance for the arrangement of Old World Phasmatodea are discussed in some more detail below.

1) The conspicuous lanceolate or foliaceous cerci are frequently found throughout anareolatae Old World Phasmatodea but can with quite some certainty be put down to a single genealogical lineage, which must have separated from the stem of Phasmatodea rather early in the evolution of the order ( Bradler, 2001: 183). Laterally compressed cerci are also found in other subgroups, but they are never structured in the typical manner of Lanceocercata. In Lanceocercata they are usually formed by flattened, leaf-like extensions of the dorsal and ventral surfaces and the apex of the cercus ( Figs. 2–19). They vary considerably in size and shape amongst the taxa of Lanceocercata and even show variation within individual tribes here interpreted as monophyletic (e.g. Phasmatini & Monandropterini ). The enlarged and specialized cerci do not serve as forceps to grasp the ♀ abdomen during copulation like, for instance, in certain members of the New World Diapheromerinae : Diapheromerini Kirby, 1904 (e.g. Diapheromera Gray, 1835 or Pseudosermyle Rehn, 1906 ) but they do in certain genera of Phasmatinae and Tropidoderinae have the basal portion set with minute denticles. During copulation these serve for the ♂ as an additional anchorage to hold fast by being pressed tightly against the lateral surfaces of the ♀ subgenital plate (Figs. 432 & 434). The conspicuous dorsal tooth of the cerci in ♂♂ of Monandropterini and Gigantophasmatini trib nov. (subfamily Tropidoderinae ) may have a similar function ( Figs. 11–16).

2) Bradler (2001: 181) stated the vomer of ♂♂ to be completely extinct in Lanceocercata which however only concerns to the external part of that organ ( Figs. 38, 39 & 42; → 3.2). The vomer is part of the phasmatodean ground plan and in Phasmatodea consists of two parts, an internal part and an often well sclerotised external part (Zompro, 2004: 24). The external part is often increasingly reduced secondarily in taxa which have it functionally replaced by a split anal segment that serves as a clasping apparatus to hold fast to the ♀ abdomen during copulation. But although the external part is reduced or lacking the internal part is still present as a desclerotized structure concealed by sternum XI (= paraproct). Indeed, the vomer is not visible without internal examination and removing of the paraprocts in all of the taxa which Bradler (2001) placed in Lanceocercata. However, an increasingly reduced vomer is also true for other subgroups e.g. the related subfamilies Clitumninae and Lonchodinae ( Figs. 35–36, 40–41), both of which also have it functionally replaced by a clasping apparatus formed by the anal segment. Hence, the lack of an external vomer in general can well be presumed as apomorphic but it can hardly be interpreted an autapomorphy of Lanceocercata.

3) The function of an anchorage to hold fast to the ♀ abdomen during the copulation is replaced by a conspiuous clasping apparatus of the ♂♂ anal segment. This is of a very characteristic shape and structure and found in almost all the taxa that Bradler (2001) included in Lanceocercata. The anal segment (= tergite X) is strongly tectiform, longitudinally split and consists of two movable semi-tergites which are merely connected by a thin membrane dorsally ( Figs. 2–19, 32–34). The ventro-apical angles are ± distinctly elevated and in some taxa even form a finger-like, in-curving process (e.g. Podacanthus Gray, 1833 or Parapodacanthus Brock, 2003 ). This processs either bears several terminal teeth, or the internal surfaces of the semi-tergites ventro-apically bear a longitudinal bulge or ledge, which is armed with a variable number of back-curving teeth ( Figs. 32–34).

A split anal segment which consists of two movable semi-tergites to form a clasping apparatus is also frequently found in ♂♂ of the subfamilies Clitumninae (→ 5.) and Lonchodinae (→ 5.5). These are however of a rather distinct structure, having the complete apex ± elongated, finger or spatula-like and with the interior surfaces almost entirely or at least along the outer margins set with small teeth ( Figs. 35–36, 20–25, 29–31). Most members of these two subfamilies have the external vomer increasingly reduced and often lacking, but it is in some genera present as a rather small papillate or filiform but well sclerotized organ (→ 5.3). Another example for a strongly reduced external vomer and a specialized a clasping apparatus of the anal segment is the Old World subfamily Eurycanthinae (→ 4.1).

As a result, it is not the split anal segment itself but the particular shape and structure of the clasping apparatus which might be regarded an autapomorphy of Lanceocercata. A split anal segment which consists of two movable semi-tergites may rather be interpreted a synapomorphy of Lannceocercata + Clitumninae + Lonchodinae + Eurycanthinae , supposing relationship between these groups.

4) Already Bradler (2001: 183) himself doubted the true apomorphic nature of the sharply keeled and boat-shaped subgenital plate of ♀♀ of Lanceocercata. Indeed longitudinally keeled subgenital plates are frequently found in most other subgroups of Phasmatodea , e.g. the related Clitumninae , Eurycanthinae or sections of Lonchodinae . As Bradler stated it is a supposition for the derived copulation position of Lanceocercata in which ♂♂ grasp the longitudinal keel close to the base of the subgenital plate and true for all taxa contained in Lanceocercata. Its presence in other not closely subgroups, none of which exhibit the same conspicuous copulation habit and often have a praeopercular organ and/or a well developed external vomer in ♂♂, suggests it must not necessarily be a specialization dependent on the copulation behaviours. It can thus hardly be an autapomorphy of Lanceocercata.

5) The derived copulation position observed in Lanceocercata is indeed remarkable and differs from all other extant Phasmatodea . In contrast to the remaining Phasmatodea , even ones without an external vomer, ♂♂ of all taxa of Lanceocercata grasp the ♀ abdomen along the distinct longitudinal median keel of the subgenital plate (= sternum VIII), which is well supported by the conspicuous longitudinal interior row of teeth or terminal teeth on the ventro-apical elevation of the anal semi-tergites of the (Figs. 431–435). Other groups which lack an external vomer (e.g. Clitumninae or Lonchodinae ) and have an anal segment that forms a clasp- ing apparatus have ♀♀ with a ± well developed praeopercular organ on sternum VII, formed by a pair of humps, laterally compressed spines or lobes (→ 5.). These appendages of the ♀♀ praeopercular organ are then grasped and used as an anchorage by the ♂♂, the shape of the appendages usually correlating with the shape of the anal semi-tergites of the ♂♂ (Figs. 436–437). Other groups, like sections of the New World subfamily Diapheromerinae , have the vomer functionally replaced by elongated, forceps-like cerci to enable the ♂♂ to grasp the ♀ abdomen during the copulation. In all those taxa with a sclerotised external vomer in ♂♂, these hold fast to the ♀ abdomen by inserting this hook-like organ into a hole, slit or special external structure (= praeopercular organ) on sternum VII of ♀♀. Consequently, the conspicuous copulation position can obviously be regarded an autapomorphy of the Lanceocercata.

Another apomorphic feature of Lanceocercata not mentioned by Bradler (2001) is the lack of a praeopercular organ in ♀♀ which correlates with the lack of an external vomer in ♂♂. The ♀♀ of neither taxon of Lanceocercata have any hint of a praeopercular organ on sternum VII, hence this structure can be regarded as lacking in this particular group of Phasmatodea . The lack may be explained by the derived copulation position for which a praeopercular organ has apparently become unnecessary.

A common feature of the eggs of Lanceocercata is the presence of a capitulum which however may be of various shapes and structures. All have closed capitula (for a definition see: Clark-Sellick, 1988: 275), which are either hat-like with a ± stalk, knob-like and closely appressed to the operculum, or conical without a stalk.

However, despite these common and obviously homologous morphological features of the insects, two fundamentally distinct types of internal micropylar plates are observed amongst the eggs of the taxa contained in Lanceocercata—open and closed plates. The structure of the internal micropylar plate may well serve for an arrangement of the subgroups of Lanceocercata and should be taken into account, since its type of shape (open or closed), and presence or absence of a median line, are obviously uniform within an individual tribe (Clark- Sellick, 1998: 204, → 4.3). Amongst Lanceocercata the internal micropylar plate is open in sections of Phasmatinae ( Phasmatini and Acanthomimini ), sections of Tropidoderinae (tribes Tropidoderini and Monandropterini ), but closed in Extatosomatinae , Gigantophasmatini trib. nov. (subfamily Tropidoderinae ), Acanthoxylini (subfamily Phasmatinae ) and “ Platycraninae ”. The internal plates of Pachymorphini (szubfamily Pachymorphinae ) are not known. The presence of both types of plates in Xeroderinae sensu Bradley & Galil, 1977 (closed in Cotylosoma Wood-Mason, 1878 and Nisyrus Stål, 1877 but open in Dimorphodes Westwood, 1859 ), suggests this latter subfamily is polyphyletic or deserves splitting into two separate tribes (→ 4.6.2).

As a result, the monophyly of Lanceocercata is well supported by morphological features of the genital exosceleton (see also: Tilgner, 2002) and indeed some of the features emphasized by Bradler (2001) appear to be autapomorphies of a supposedly monophyletic group. But, due to Lanceocercata contains the subfamily Phasmatinae with the subordinate taxon Phasmatini and the type genus Phasma, Lanceocercata represent what must actually be regarded the family Phasmatidae Gray, 1835 (sensu stricto). Consequently, the term “Lanceocercata” has to be interpreted as a synonym of the available family name Phasmatidae .

For a list of the subfamilies and tribes contained in Phasmatidae s. str. see below.