Tetrigimyia minor, Shima, Hiroshi & Takahashi, Hajime, 2011

Shima, Hiroshi & Takahashi, Hajime, 2011, Tetrigimyia minor, a new genus and species of Tachinidae (Diptera) parasitic on Formosatettix larvatus (Orthoptera: Tetrigidae) in Japan, Zootaxa 2921, pp. 39-46 : 42-45

Tetrigimyia minor sp. nov.

( Figs. 1–8)

Male. Head ( Fig. 1) black in ground color, pale brownish on parafacial, face and gena below eye and reddish brown on frontal vitta, with dense whitish pruinosity, yellowish gray on fronto-orbital plate; antenna brown, pedicel and base of 1st flagellomere reddish yellow; palpus yellow. Vertex about 1/3 as wide as head width; frontal vitta about 1.5 times as wide as fronto-orbital plate at middle; parafacial narrow, narrowed below, about 1/3 as wide as 1st flagellomere at middle height; face weakly concave, lower margin weakly warped forward, only slightly extending beyond vibrissal base; gena about 1/8 of eye height; occiput flat. Inner vertical seta strong, slightly more than 1/2 of eye height; outer vertical seta about 1/2 as long as inner seta; ocellar seta short and fine, about 1/2 as long as outer vertical seta; fronto-orbital plate with 1–2 irregular rows of several fine short hairs, not descending below lowest frontal seta; reclinate orbital seta about 2/3 as long as inner vertical seta; anterior proclinate orbital seta as long as reclinate orbital seta, posterior seta fine, nearly as long as ocellar seta; 3–4 frontal setae, lowest seta nearly level with middle of pedicel; facial ridge with a few fine short setae just above vibrissa; gena with a few fine hairs on occipital dilation. Antenna shorter than height of face by about length of pedicel; 1st flagellomere 3.5–4 times as long as pedicel. Palpus weakly clavate, slightly shorter than 1st flagellomere.

Thorax dark brown to black in ground color, scutellum paler; dorsum with dense pale yellowish gray pruinosity, scutellum with very thin grayish pruinosity; 4 distinct longitudinal vittae on presutural area of scutum and postsutural scutum, median vittae fused and forming rectangular spot on postsutural scutum; pleura with thin grayish pruinosity. Scutellum nearly triangular in form, apex rather rounded; discal seta short and fine, about 1/2 as long as scutellum; basal scutellar seta about 2 times as long as scutellum; lateral scutellar seta short, slightly shorter than scutellum; subapical scutellar setae strong, weakly divergent, slightly longer than basal seta. Wing ( Fig. 8 ) hyaline, weakly and evenly tinged with pale brown; tegula black; basicosta pale brown; lower calypter translucent pale brown; halter pale yellowish; costa from apex of subcosta to vein R1 about 1/3 as long as that from veins R1 to R2+3 and about 2/3 as long as that from veins R2+3 and R4+5; vein M from dm-cu crossvein to its bend about 3/4 as long as that from r-m to dm-cu crossveins, and only slightly longer than that from the bend to apex of vein M; ultimate section of vein CuA1 about 2/3 as long as dm-cu crossvein; halter knob large, about 2 times as large as metathoracic spiracle. Legs yellowish, claws pale yellow; claws and pulvilli shorter than 5th tarsomere.

Abdomen broadly reddish yellow in ground color, apical 1/3 of 4th tergite dark brown, apical portion of 5th tergite sometimes brownish; very thin whitish pruinosity only on anterior margin of 4th tergite and anterior 1/3 of 5th. Syntergite 1+2 weakly excavated on anterior 1/2, sometimes with 2 weak median marginal setae, which are about 3/5 as long as 3rd tergite, and 1 lateral marginal seta; 3rd tergite with 2 median marginal setae, which are about 4/5 as long as 4th tergite, and 1 strong lateral marginal seta; 4th and 5th tergites each with a row of strong marginal setae.

Male terminalia: Fifth sternite with rounded projection on posterointerior margin of posterior lobe ( Fig. 5 ); cerci narrowly separated on apical 2/ 5 in dorsal view; surstylus weakly curved ventrally, with several minute setulae ( Figs. 2–3 ); pregonite narrow, with several hairs on posterior margin; postgonite flat, narrowed apically; epiphallus short, knob-like in form; distiphallus with narrow dorsal and broad ventral sclerites, ventral margin serrate ( Fig. 4 ).

Female. Closely resembling male but differing as follows: 2 proclinate orbital setae subequal in length or posterior seta slightly shorter; antenna shorter, falling short of lower margin of face by about 2/3 length of 1st flagellomere, the latter about 3 times as long as pedicel; abdomen reddish brown with dark brownish transverse bands on posterior 1/3–1/4 on syntergite 1+2 to 4th tergite, which are broadly interrupted mid-dorsally; 5th abdominal tergite reddish yellow, conical and narrowly truncated at apex, directed downward. Female terminalia ( Fig. 6 ): Intersegmental membrane between 5th and 6th segments longer than 5th sternite; 6th tergite of long triangular hemitergites, weakly sclerotized, with several fine setae on posterior margin; 6th sternite about 1.5 times as long as 5th sternite, with several setae on posterior portion; 7th tergite sclerotized only on short posterior portion, with several fine setae on posterior margin; 7th sternite of small semicircular sclerite, with dense fine setae; 8th sternite of a very small sclerite, with several fine setae; epiproct small, without hairs.

Body length: 3.1–4.3 mm.

Holotype male, Akagawa-onsen, Takeda City, Mts. Kuju, Oita Pref., Japan, 27.iv.2009 (date of adult emergence), ex Formosatettix larvatus, H. Takahashi ( BLKU).

Paratypes: All ex Formosatettix larvatus , 2 males, Karasawa, Hanno City, Saitama Pref., 25.iv.2009 (date of adult emergence), I. Wada ( BLKU); 5 males 4 females, Akagawa, Takeda City, Oita Pref., date of adult emergence as follows: 13,23,24. iv.2009, 17,19.vii.2009, 5.ix.2009, 31.x.2009, 1,11. xi.2009, H. Takahashi (KUM).

Other material examined. All ex Formosatettix larvatus , date showing adult emergence; Natsui, Tainai City, Niigata Pref., 2 females, 13.viii.2008, H. Takahashi; Karasawa, Hanno City, Saitama Pref., 1 male 1 female, 25.v.2009, I. Wada; Mt. Takao, Hachioji City, Tokyo, 1 female, 2.vii.2009, H. Takahashi; Mt. Daisen, Tottori Pref., 2 males 2 females, 16,19. v.2009, H. Takahashi; Akagawa-onsen, Takeda City, Mts. Kuju, Oita Pref., 3 males 4 females, 23.iv.2009, 1 female, 24.iv.2009, 2 males 1 female, 25.iv.2009, 3 males 5 females, 27.iv.2009, 1 female, 28.iv.2009, 1 female, 17.vii.2009, 2 males, 19.vii.2009, 2 females, 23.vii.2009, 1 female, 1.viii.2009, 1 female, 30.x.2009, 1 male, 1.xi.2009, 1 male, 3.xi.2009, 1 male, 2 females, 7.xi.2009 ( BLKU, KUM).

Host. Formosatettix larvatus Bei-Bienko ( Orthoptera , Tetrigidae ).

Etymology. The specific name refers to the small body size of this species.

Distribution. Japan (Honshu & Kyushu).

Biology. Formosatettix larvatus is apterous and its adults and larvae are found in dark undergrowth of elm woods eating dead and decaying leaves. Tetrigimyia minor is oviparous; females lay planoconvex elliptical eggs (0.5 mm long, 0.25 mm wide) on the ventrolateral portion of host abdomen. Parasitized adults or larvae were found in April (Akagawa, Oita Pref.), May (Karasawa River, Hanno City and Mt. Daisen, Tottori Pref.), and June and October (Akagawa). This tachinid appears to have at least two generations a year, adults appearing in late spring and again in summer. It is possible that the tachinid overwinters as a 2nd or 3rd instar in the host’s body. Percentages of parasitism of this fly were high at Akagawa, but rather low at Karasawa and Mt. Daisen ( Table 1).

The first instar tachinid larva emerges through the operculum of the egg within a week after oviposition and penetrates into the host haemocoel through the abdominal intersegmental membrane, moving at least 1.6 mm apart from the egg. Second and third instars form a respiratory funnel attached to a host abdominal spiracle. Dissection of dead hosts revealed that there were more than one (up to five) tachinid larvae per host. Usually only one mature larva emerged from a host and pupated, but in some cases two successfully emerged and eclosed.

Locality Collection date F. l a r v a t u s unparasitized parasitized Total

larvae adults

Akagawa April 11 Adult males 6 1 1 2 9 Adult females 8 1 1 1 10 Larval males 3 2 - 5 Larval females 1 4 - 5

Percentage parasitism: 37.9%

Akagawa July 7 Adult males 4 - - 4 Adult females 4 - 2 6 Larval males 13 4 - 17 Larval females 10 4 - 14

Percentage parasitism: 24.4%

Akagawa October 11 Adult males 1 - - 1 Adult females 1 - - 1 Larval males 4 8 - 12 Larval females 5 5 - 10

Percentage parasitism: 54.2%

Karasavwa May 11 Adult males 7 1 1 1 9 Adult females 11 - - 11

Percentage parasitism: 10.0%

Mt. Daisen May 2 Adult males 11 2 1 - 13 Adult females 11 - - 11 Larval males 2 - - 2 Larval females 3 - - 3

Percentage parasitism: 6.9%

1Parasitized adults without entrance holes of parasitoid larvae on their bodies are considered to have been parasitized as larvae.

Figures

FIGURES 7 – 8. 7. Habitus of Tetrigimyia minor sp. nov., female. 8. Right wing of Tetrigimyia minor sp. nov.

FIGURES 2 – 6. Terminalia of Tetrigimyia minor sp. nov. 2. Male epandrium, cerci and surstylus in dorsal view (hairs omitted). 3. Same in lateral view (hairs on epandrium omitted). 4. Male hypandrium, pregonite, postgonite and phallus in lateral view. 5. Male 5 th sternite in ventral view (hairs on left side omitted). 6. Female terminalia in lateral view. Scale: 0.1 mm.