Microporus thoreyi (Signoret, 1882)

Microporus thoreyi (Signoret, 1882) is a poorly known but visually striking member of the heteropteran family Cydnidae (burrower or burrowing bugs) ( Larivière & Larochelle 2004). It has a shiny black, broadly oval body, and on first glance is easily mistaken for a dorsoventrally flattened beetle ( Fig. 1). It has light, orange-brown legs that have a fossorial appearance and prominent bristles along the margins of the thorax. The front of the head (anteocular margin) bears prominent, short stout pegs interspersed with longer bristles. Body length of the three specimens examined by Larivière (1995) in her description of the species ranged from 4.36 – 4.75 mm. Her account also includes a line drawing of M. thoreyi and sketches of the female first gonocoxae and metathoracic scent gland opening. An excellent photograph of the species is provided by Thorpe (2012).

M. thoreyi also occurs in Australia, and is assumed to have been introduced to New Zealand ( Larivière & Larochelle, 2004). However, because nothing had been written about it between the time of its original description as Cydnus thoreyi in 1882 (and its inclusion in Lethierry & Severin’s catalogue of Hemiptera in 1883), and her 1995 account of the species, Larivière considered it to be an “enigmatic taxon”.

The New Zealand material examined by Larivière (1995) consisted of one male and two females collected in pit-traps in Woodhill Forest west of Helensville (AK), and at Ruakaka south of Whangarei (ND). The type material (a single specimen on which the original description was based) could not be located. More recently, Thorpe (2012) reported the finding of another male in a pit-trap in Shakespear Regional Park, Whangaparaoa Peninsula (AK).

New record from Northland

Two female specimens of M. thoreyi were found at Lake Heather , a sand dune lake in Northland on 13 February 2012. They were taken in a sweep sample of emergent aquatic vegetation at the margin of the lake while one of the authors (SRP) was searching for larval Odonata and other aquatic invertebrates. We assume the two burrower bugs were on emergent stems or leaves as several unidentified spiders, ants and a weevil were also present in the same sample. This appears to be the first New Zealand record of M. thoreyi taken close to water and the first not collected in a pit-trap. Body lengths of the two females were 4.6 and 4.0 mm, making the latter the smallest individual known.

Lake Heather (35 o 3.05’ S, 173 o 11.62’ E) is 5.5 km west of Awanui near the base of the Aupouri Penisula in the far north of New Zealand. It is not named on official NZMS maps or on Google Earth but lies due north of, and adjacent to, the larger Lake Rotoroa, which is identified by these sources. The lake is 39 m above sea level and has a sandy catchment with land cover dominated by pasture and rough scrub. Emergent vegetation around the lake, including the sampling area, was dominated by the spike rush Eleocharis sphacelata , with a sedge ( Baumea articulata ), raupo ( Typha orientalis ), a second spike rush ( E. acuta ) and introduced alligator weed ( Alternanthera philoxeroides ) also present ( Wells et al. 2007). Sweep samples taken from the same part of the lake on six occasions between February and December 20011, and in November 2008 included no specimens of M. thoreyi .

The Lake Heather specimens represent the northernmost record of M. thoreyi in New Zealand, being about 200 km north of both Ruakaka and the Woodville Forest site. Their apparent presence on emergent vegetation close to a lake shore suggests these phytophagous bugs may not be solely root feeders as has been assumed ( Larivière & Larochelle 2004).