Family PACHYGRONTHIDAE

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Family PACHYGRONTHIDAE

Compiler and date details

15 February 2002

Introduction

The Pachygronthidae are a moderate-sized family of monocot-feeding lygaeoid bugs presently comprising 13 genera and 78 species (Slater & O'Donnell 1995; Zoological Record 1995–2001). They are found in all major zoogeographic regions and are largely tropical and subtropical in distribution. The Australian fauna comprises six genera and ten species.

Stål (1865, 1870, 1874) provided the first synthesis of the suprageneric group. From Distant (1882) onwards, pachygronthids have largely been considered to form a subfamily of the Lygaeidae sensu lato. Slater (1955) reviewed the group and considered it to have a basal phylogenetic position within Lygaeidae. Henry (1997) raised the subfamily to family level, as Pachygronthidae, and established the Blissidae as their sister-group.

Stål (1874) recognised two tribes among pachygronthids: Pachygronthini and Teracrini. Slater (1955) claimed that these tribes are dissimilar morphologically, but did not dispute a close relationship, based primarily on the ventral position of the abdominal spiracles. These two tribes are raised to subfamily and the classification used in the Catalogue is as follows: Pachygronthidae: Pachygronthinae and Teracrinae.

The Pachygronthinae have a circumtropical distribution. Slater (1955) divided the nominotypical genus, Pachygrontha Germar, into eight species-groups, which are mostly restricted to either the eastern Palaearctic, Oriental, Afrotropical or Neotropical Regions. The Australian fauna is relatively depauperate and composed of five pachygronthine species (2 endemic), most of which are confined to the tropics. Pachygrontha bipunctata bipunctata (Stål) is also widespread throughout the Eastern Hemisphere tropics. Slater (1955) argued that the Australian Pachygrontha species are an extension of the Oriental fauna. The subfamily is also represented in Australia by the monotypic endemic genus Magninus Distant, which is restricted to coastal areas (Albany and Warren River) of south-western Western Australia.

The Teracrinae comprise seven genera and 22 species (Slater 1964; Slater & O'Donnell 1995), and, aside from Phlegyas (Western Hemisphere), are found in the Eastern Hemisphere, particularly in the tropics. Opistostenus Reuter and Stenophyella Horváth have Indo-Pacific distributions and each is represented in Australia by an endemic species. Darwinocoris Slater and Stenophlegyas Slater are endemic monotypic genera; D. australicus Slater is restricted to southern Western Australia (King George's Sound) and S. woodwardi Slater is known from disjunct locations in Queensland.

Slater (1955, 1956, 1962, 1978) reviewed the Australian fauna, describing two new genera and four species. Aside from the ubiquitous Stenophyella macerta Horváth, pachygronthids are not well represented in museum collections.

Knowledge of the biology of Pachygronthidae is very limited. Most species are monocot-feeders and are thought to be 'up-on-plant' seed-predators. They are known from plant species of the Poaceae, Cyperaceae and Restoniaceae. In Australia Pachygrontha robusta Slater is known from the widespread sedge genus Gahnia J.R.&G.Forst; one of us [GC] has also found undetermined species of Pachygrontha associated with Gahnia species. Darwinocoris australicus Slater is known from the restio, Leptocarpus coangustatus Nees. Stenophyella macerta is one of the most abundant heteropterans in Australia and is commonly taken when sweeping grasses. Malipatil & Kumar (1975) and Slater (1976a, 1976b) provided biological notes on Australian pachygronthids.

Diagnosis

Pachygronthids are slender, elongate species, that are generally pale in colour. The head is declivent and the bucculae are short. The antennae are elongate and filiform or weakly fusiform. The first segment either greatly exceeds the clypeus (Pachygronthinae) or barely reaches the apex of the clypeus (Teracrinae). The pronotum is trapeziform, usually with a shallow transverse impression medially. The forefemora are incrassate and are armed with prominent spines. The costal margins of the hemelytra are not explanate and do not extend over the connexiva. The hemelytral membrane possesses simple veins that are neither anastomising nor connected by cross-veins. Most species are macropterous, although brachypterous morphs are known. All the abdominal spiracles are ventral. The abdominal sutures are straight and extend to the lateral margins. The male parameres are symmetrical and either have a tuft of sensory hairs (Pachygronthinae) or lack them (Teracrinae). (Slater 1955; Schuh & Slater 1995; Henry 1997)