Diphamorphos graminis, Schmidt, 2005

Schmidt, Stefan & Brown, Graham, 2005, A new genus and species of Australian pergid sawfly (Hymenoptera: Symphyta, Pergidae) causing damage on grass (Poaceae), Zootaxa 955, pp. 1-8 : 2-5

Dalia graminis , Schmidt, new species ( Figs 1–9 )

Type Material. Holotype female. Australia, Northern Territory, Douglas Daly Research Farm, 25.ii.1990, M. Neil, 47765, ex Digiterea sp. Type deposited in Museum & Art Gallery of the Northern Territory, Darwin, Australia ( MANT). Paratypes 9 females, same data as holotype (5 in MANT, 4 in Zoologische Staatssammlung München, Munich, Germany ( ZSM)); 3 females, Early Storms, Douglas Daly Region, 7.xii.2001, M. Plant, reared from larvae on grass Pennisetum typhoides , (2 in MANT, 1 in ZSM); 2 larvae dry mounted ( MANT (sample no. 44473), ZSM); 20 larvae in ethanol (10 in MANT (sample no. 44473), 10 in ZSM),

Female. Length, 4.5–5.0 mm. Head brown except clypeus and labium yellow–brown. Thorax orange, legs light brown, apical tarsal segments dark brown. Antenna with basal 4– 5 segments yellow­brown and remaining segments dark brown. Abdomen brown. Wings with brown tint, venation including fore wing stigma dark brown.

Antenna, 12–segmented, segments 4–7 subserrate ( Fig. 1 ); first flagellar segment as long as two following segments; subapical segments broader than long (subapical segment ~1.5X broader than long); apical segment conical and slightly broader than long or as long as broad. Eyes suboval, bare, ~1.5X broader than their maximum length, slightly converging towards clypeus in frontal view. Head behind eyes subparallel in dorsal view ( Fig. 2 ); postocellar area length ~0.5X its maximum width; anterior ocellus separated from lateral ocellus by distance equal to diameter of lateral ocellus ( Fig. 2 ); malar space very narrow, ~0.1X maximal diameter of anterior ocellus; clypeus truncate; left mandible with small inner tooth, right mandible simple. Vertex densely punctured but shiny between punctures and covered with pale setae ( Fig. 2 ); postocellar area scarcely setose and shiny. Thorax smooth and shiny with white setation; abdomen with weak transversely rugose surface sculpture, shiny. Inner spur of fore tibia smaller than outer one; apical tibial spurs of midtibia of equal length; hind basitarsus subequal in length to following two tarsal segments. Sheath in dorsal view apically widened with blunt apex. Lancet short, lamnium consisting of 8–9 segments, each annulus (proximal edge of segment) with 4–5 large teeth ( Fig. 5 ). Serrulae very shallow, without subserration.

Male. Unknown.

Larva. Length of full grown ethanol–preserved specimen about 15 mm. Living larvae are dorsally grey and ventrally whitish with dark brown head which is lighter below eyes ( Fig. 7 ). Colour of ethanol–preserved specimens as follows ( Fig. 6 ): head above brown, yellowish below eyes, clypeus white; antenna brown on white base. Body grey–brown dorsally down to level of suprapedal lobes, ventrally whitish. Thoracic legs laterally and abdominal prolegs anteriorly brownish ( Figs 6 , 7 ).

Head sparsely setose; setae short, 1– 3 X diameter of an eye; antenna 2–segmented. Annulets of pro– and mesothorax dorsally slightly bilobed. Abdominal segments 1–8 each with four annulets and with following number of pale tubercles: 1: 2 (dorsal), 2: 6–8, 3: 0, 4: 6; each tubercle with one to several warts. Apical segment of abdomen (supra–anal lobe) with many warts and posteriorly with several setae. Abdominal segments 1–8 and 10 with prolegs; prolegs of abdominal segments 1 and 2 reduced. Prolegs anteriorly with several setae, those of segment 10 also laterally and posteriorly with setae. Cocoon black with single wall ( Figs 8, 9 ).

Host plant. Digiterea sp., Pennisetum glaucum (L.) R.Br. ( Poaceae ).

Comments. This species is known from two sites of cleared woodland near the junction of the Douglas and Daly Rivers. The soil is red sand. The larvae are grass­feeders and may occur in such large numbers that they reach plague proportions, appear like armyworms ( Noctuidae ), and completely defoliate host plants. The preferred hosts are Digitera sp. and Pennisetum glaucum which appears to grow in open areas. When this food source is consumed they will move into adjacent stands of agricultural crops including sorghum and dry land rice. They are able to survive to maturity on these plants, but have only been found on the margins of these taller crops.

Pupation occurs at or near the base of the plant in a black ovoid cocoon ( Figs 8, 9 ). The cocoon is amongst the leaf litter. It is impossible to locate without sieving as, although the cocoon is black, it is covered with sand grains and amongst frass, and, thus, well camouflaging ( Fig. 9 ). In the laboratory, larvae were first found to pupate within bundles of grass stems that had been held together with rubber bands. This was a convenient method of handling food supplies for the larvae and coincidently provided a suitable pupation site.

Adults are slow fliers and occur close to the ground. They can be difficult to locate as the preferred host plant is relatively open and the wasp is camouflaged by red soil and accumulated frass in the background.

The number of generations per annum is unknown. There are probably several, but numbers and seasonality are related to rainfall. Larvae collected in mid December produced the adults in late January under laboratory conditions.

Figures

FIGURES 1 – 6, Dalia graminis: 1, Antenna in lateral view, 2, Head in dorsal view, 3, Fore wing, 4, Hind wing, 5, Lancet, 6, Full grown larva.

FIGURES 7 – 9, Dalia graminis: 7, Larva feeding on host plant, 8, Eonymph removed from cocoon, with remains of cocoon on right, 9, Cocoon.