Stenodiplosis eragrostidis Felt, 2020

Kolesik, Peter & Gagné, Raymond J., 2020, A review of the gall midges (Diptera: Cecidomyiidae) of Indonesia: taxonomy, biology and adult key to genera, Zootaxa 4847 (1), pp. 1-82 : 66-68

Stenodiplosis eragrostidis Felt , new combination

[ Figs 39 a–g]

Contarinia eragrostidis Felt, 1927b: 381 .

Material examined. Types: 9 males, 11 females ( NYSM #a3440), reared from seed heads of Eragrostis unioloides (Retz.) Nees ex Steud. , collected by C.A. Backer at Bogor, Java [see DvLR & DvL (1941) for this locality], viii-1922. The type series is mounted on two slides, one with 4 males and 5 females, the other with 5 males and 6 females, all whole and uncleared. Most characters are well-preserved in at least one of the specimens, except for the male terminalia that are mostly shriveled in all the males.

Description. Male. Length 1 mm ( Felt 1927b), wing length 1.2 mm (1.1–1.4), width 0.4 mm (0.4–0.5). Palpus 1-segmented [as in Fig. 39e ]. Antenna: 12 flagellomeres, first and second fused; flagellomeres binodal, each node with one whorl of looped circumfila, basal node slightly wider than long, distal slightly longer than wide, internode one third length of basal node, neck half-length distal node; circumfilar loops subequal, on basal node reaching end of internode, on distal node reaching end of neck [ Fig. 39c ]. Wing with R 5 slightly bowed at distal ¼, joining C slightly beyond wing apex [ Fig. 39a ]. Tarsal claws simple, curved beyond midlength, widened beyond bend, empodia as long as claws [ Fig. 39b ]. Abdominal tergites lacking lateral setae. Terminalia: gonostylus stout, strongly tapering from wide base towards tooth, completely setulose [ Fig. 39d ].

Female. Length 1.5 mm ( Felt 1927b), wing length 1.2 mm (1.1–1.4), width 0.4 mm (0.4–0.5). Antenna: flagellomeres about 2.5x longer than wide, neck 1/7 total length, node with shallow, bare constriction at midlength, each half of flagellomere with separate whorl of looped circumfila, loops on basal half reaching constriction, loops on distal half nearly reaching end of neck [ Fig. 39f ]. Terminalia: ovipositor as long as abdomen; cerci [ Fig. 39g ] closely appressed, tapered, about 2.5 longer than basal width, without microtrichia and with setae of various sizes.

Pupa, larva, unknown.

Remarks. We transfer this species to Stenodiplosis Reuter , a Holarctic group presently comprising 12 species, all of them associated with grass seeds, some of considerable economic importance ( Gagné & Jaschhof 2017). The most important relevant adult character for this generic placement is the lack of lateral setae on the abdominal tergites ( Gagné 2018 ). Many Stenodiplosis spp. exhibit a reduction in palpal segments, so S. eragrostis also fits that criterion with its single segment. Not an exclusive character, but most Stenodiplosis species have fully setulose gonostyli, as does this species. Larval characters also define the genus, including the loss of the larval spatula, the miniscule terminal segment and terminally situated hind spiracles. The larva of S. eragrostidis is unknown, but we expect that it shares these character states.

Felt (1927b) stated that the male palpi were indistinguishable in the mounted specimens and that the female had a four-segmented palpus. We found that the palpi are one-segmented in both sexes, as did Harris (1979) who also examined the type series. When Harris (1979) described Contarinia brevipalpis from the inflorescence of Eragrostis brownii in tropical Australia, he noted that it shared with C. eragrostidis the one-segmented palpus, and the binodal female flagellomeres that bear two whorls or circumfila. Additionally, these two species share the shape of the gonostylus and female cerci, also the relative length of internodes and necks in both male and female flagellomeres. They can be separated by the tarsal claws that are shorter and less curved in C. brevipalpis ( Harris 1979, Fig. 44) than in C. eragrostidis [ Fig. 39b ] and by the setation of female cerci that bear apically two pairs of long setae in C. brevipalpis ( Harris 1979, Fig. 36 ) and one pair in C. eragrostidis [ Fig. 39g ]. These differences may turn out to be very minor but, without Harris’s types and additional specimens before us, we cannot make a decision at this time. We take the occasion to place C. brevipalpis in Stenodiplosis also, as a new combination.

Biology. Contarinia eragrostidis causes slight swelling and developmental retardation of seed heads of Eragrostis unioloides (Poaceae) , with the gall approximately 5 mm long and 2 mm in diameter ( Felt 1927b).

Geographical distribution. This species is known from Java where it was found at the type locality in Bogor, alt. 250 m, viii-1922 ( Felt 1927b; DvLR & DvL 1941). Additionally, it was found on Andaman Islands ( India): Port Blair, 27-xi-1981 ; Dhanikhari, 11-xii-1981; Manarghat, 13-xii-1982; Wandoor 24-ix-1983. Several males and females were reared and deposited in the collection of the museum of Zoological Survey of India at Port Blair ( Sharma 1984) but we have not seen these specimens .

Figures

FIGURES 36a–l. Schizomyia laporteae: a, gall on Laportea stimulans (Fig. 74 of DvLR & DvL 1910b); b, same (Fig. 221 of DvLR & DvL (1926)); c, apex of gonopod (ventral); d–f: pupa: d, head; e, thoracic spiracle; f, abdominal tergum 6 (lateral); g, female first tarsomere; h, male palpus; i–l, female: i, tarsal claw and empodium; j, ovipositor apex; k, 3rd flagellomere; l, antenna.

FIGURES 39a–g. Stenodiplosis eragrostidis: a–d, male: a, wing; b, last tarsal segment of hind leg with claw and empodium; c, 6th flagellomere; d, gonostylus (dorsal); e–g, female: e, palpi; f, 6th flagellomere; g, cerci (dorsal).