NSW Scientific Committee - final determination
The Scientific Committee has found that:
1. Panesthia lata (Dictyoptera: Blattaria: Blaberidae: Panesthiinae) is a wood-feeding cockroach first described by Walker in 1868. The following description is from Roth (1977). Male: Head punctulate, ocellar spots not round, vertex not foveolate, exposed. Pronotum convex, anterior margin very slightly concave, incrassate, with a small mesal rounded elevation; anterior half moderately depressed, the floor sparsely roughened and with fine transverse striae; laterally finely and sparsely punctate, mesal disc tubercles represented by low, rounded mounds. Meso- and metanotum with very few, fine punctations. Mesonotum not reaching the margin of the body, the anterior half, or the entire lateral margin, covered by the tegmina. Tegmina lateral, reaching slightly beyond hind margin of mesonotum. Wings absent. Tergites hairless, shallowly punctate, the punctations more numerous on posterior segments; anterolateral corners of T5-T7 with small holes lacking setae, the opening on T5 very small. Lateral margin of segment 7 practically straight, the caudal angle short, stout, directed caudad. Supranal plate densely punctate, hind margin arcuate, entire, the lateral angle short, rounded. Sternites shallowly punctate, punctations most numerous on S7 whose hind margin is concave. Cercus subrectangular, dorsoapical surface punctulate but lacking setae, ventrally with a setose swelling below apex. Anteroventral margin of front femur with 1-2 spines and a small distal spine, hind margin with a large distal spine. Genital phallomeres well developed. Total length 33-40 mm; pronotum length x width 7.8-9 x 13-14.5 mm; tegmen length x width 4.5-5.7 x 2.8-3.6 mm. Colour is somewhat metallic, shiny. Head reddish to black, apex of clypeus and base of labrum tawny, remainder of labrum brownish, the apex darker. Pronotum with disc blackish, blending into reddish. Meso- and metanotum and anterior abdominal tergites blackish. Mesal edge of tegmen pale. Abdominal sternites black, legs reddish.
Female differs from male as follows: Anterior pronotal margin slightly concave, but not incrassate and lacking the mesal elevation. Anterior half of the pronotum less depressed and punctate and without elevated mounds of tubercles; in their place may be a pair of round, slight depressions. The female is generally blacker than the male, showing less of the reddish tinge and lacking the metallic shine. The apical clypeal band is also much narrower than in the male. Anteroventral margin of front femur with 2 spines. Total length 32.5-41 mm; pronotal length x width 7.5-9.2 x 12.5-16 mm; tegmen length x width 5-6.4 x 3-3.8 mm (Roth 1977).
The female nymph (18 mm) has meso- and metanotum and abdominal tergites densely punctate, holes in anterolateral corners of T5-T7, and hind margin of the supranal plate entire (Roth 1977).
There are 7 specimens of Panesthia lata in the Australian Museum and 5 at the University of Sydney (collection of H. A. Rose)
2. Close relatives of Panesthia lata exist throughout the eastern states of mainland Australia. Panesthia lata is endemic to Lord Howe Island (Roth 1977) where it is thought to have once been widespread (H. A. Rose, pers. comm.). A comment from Olliff (1889) supports this contention: "The most important members of the Orthoptera we obtained were a large Blatta, probably a new species, which is invariably found in and under decayed logs". This description is consistent with the habitat of all wood-feeding cockroach species throughout parts of Asia, Indo-Malayan and Australian regions. On Lord Howe Island, suitable habitat exists in all lowland areas.
3. No Panesthia lata have been found on Lord Howe Island since the 1960s, despite extensive insect surveys (H. A. Rose pers. comm.). In 2003, specimens of P. lata were collected on Blackburn Is. and Roach Is. by I. Hutton and H. Rose. On Blackburn Is. specimens were only found around a single Banyan tree, Ficus macrophylla ssp. columnaris. The population size was estimated at 1 adult and 10 juveniles. On Roach Is., Panesthia lata was located adjacent to a Cyperus lucidus grass patch where they were found under rocks and feeding on Poa grass and Cyperus leaves. In another area on Roach Is., a few small individuals were found under Commelina cyanea. Only 15 adults were seen during a one-hour search (H. A. Rose, pers. comm.). Both Roach and Blackburn Island are part of the Lord Howe Island Permanent Park Preserve.
4. The apparent extinction of Panesthia lata on Lord Howe Island is probably due to rats which were introduced in 1918. Rats are not currently present on either Blackburn or Roach Islands but could be introduced accidentally to Blackburn Is. via small boat traffic. On Blackburn Is. Panesthia lata may be threatened by further spread of Rhodes grass (Chloris gayana). Rhodes grass forms thick mats which Panesthia lata is unable to penetrate (H. A. Rose, pers. comm.). Fire may also be a potential threat, especially in areas dominated by Rhodes grass.
5. In view of the above the Scientific Committee is of the opinion that Panesthia lata Walker 1868 is likely to become extinct in nature in New South Wales unless the circumstances and factors threatening its survival or evolutionary development cease to operate.
Associate Professor Paul Adam
Chairperson
Scientific Committee
Proposed Gazettal date: 13/2/04
Exhibition period: 13/02/04 - 26/03/04
References
Olliff AS (1889) Lord Howe Island: Its Zoology, Geology and Physical Characters. Australian Museum Memoirs 2, p 31.
Roth LM (1977) A taxonomic revision of the Panesthiinae of the World. I. The Panesthiinae of Australia (Dictyoptera: Blattaria: Blaberidae). Australian Journal of Zoology Supplementary Series No. 48, 1-112.