Agromyza fission, Eiseman & Lonsdale, 2018

Eiseman, Charles S. & Lonsdale, Owen, 2018, New state and host records for Agromyzidae (Diptera) in the United States, with the description of thirty new species, Zootaxa 4479 (1), pp. 1-156: 9-10

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Agromyza fission

spec. nov.

Agromyza fission   spec. nov.

( Figs. 3–4 View FIGURES 1–6. 1 , 68 View FIGURES 63–74 , 225–229 View FIGURES 225–229 )

Holotype. IOWA: Allamakee Co., Red Oak Prairie (43°14'13.43"N, 91° 7'8.58"W), 16.vii.2015, em. 2.viii.2015, C.S. Eiseman, ex Celtis occidentalis   , #CSE1925, CNC564711 View Materials (1♂) GoogleMaps   .

Paratypes. IOWA: same collection as holotype, CNC564712 View Materials (1♂)   ; MARYLAND: Plummers Isl. , 23.v.1914, R.C. Shannon (1♂, USNM)   ; OKLAHOMA: Payne Co., Mehan , 36.014339° N, 96.996744° W, 5.iv.2016, em GoogleMaps   . 20– 22.iv.2017, M.W. Palmer, ex Celtis occidentalis   , #CSE3529, CNC939918, CNC939919 (1♂ 1♀); WISCONSIN: Buffalo Co., Alma, S 1287 State Road 88, 17.vii.2015, em   . 3.iv.2016, C.S. Eiseman, ex Celtis occidentalis   , #CSE2311, CNC634841 (1♂).

Etymology. The specific name refers to the split male cercus (L. fissus —“cleave, split”).

Host. Cannabaceae   : Celtis occidentalis L.  

Leaf mine. ( Fig. 68 View FIGURES 63–74 ) Whitish; initially linear, widening to an elongate blotch; frass dark greenish to black, forming two fine rows of beaded strips in the linear portion, and randomly deposited in scattered grains and small, irregular lumps in the blotch.

Puparium. ( Fig. 4 View FIGURES 1–6. 1 ) Yellowish-brown to orange-brown; formed outside the mine.

Distribution. USA: IA, MD, OK, WI.

Adult description. Wing length 2.3mm (♂), 2.5mm (♀). Length of ultimate section of vein CuA1 divided by penultimate section: 1.0. Eye height divided by gena height: 3.9. First flagellomere small and rounded, without pale tuft of hairs. Fronto-orbital plate slightly projecting (more so anteriorly). Ocellar triangle small and rounded. Thorax with light pruinosity.

Chaetotaxy: Two ors, two ori. Three strong dorsocentrals, anterior seta 2/3 length of second. Mid tibia without posteromedial setae.

Coloration: ( Fig. 3 View FIGURES 1–6. 1 ) Setae black. Body mostly dark brown. Head yellowish-orange with first flagellomere infuscated on distal 2/3, back of head and occiput dark brown, frons dark brown behind level of hind fronto-orbital, face white and clypeus brown to dark brown. Calypter margin and hairs brown. Haltere white. Tarsi, base of fore tibia and apex of fore femur yellow.

Genitalia: ( Figs. 225–229 View FIGURES 225–229 ) Surstylus small, lobate, setulose and slightly angled anteriorly; fused to anteroventral margin of epandrium with suture partially evident. Cercus broad and emarginate apically; inner surface covered with numerous small tubercle-like setae. Postgonite small and rounded with shallow inner lobe. Single sclerite of basiphallus fused to phallophorus on left side, twisted dextrally; distal margin forming small transverse sclerite. Mesophallus small and flat. Distiphallus composed of a single dark, flat, curved sclerite (shortest dorsally) nearly forming a complete tube; lateral margins fringed and not meeting ventrally.

Comments. The new species will key to the very similar Agromyza varifrons Coquillett in Spencer & Steyskal (1986)   , but the male cercus ( Figs. 228, 229 View FIGURES 225–229 ) is highly derived, being strongly widened apically and deeply cleft, with small, tubercle-like setae covering the inner surface. The dimensions, spacing and orientation of sclerites of the phallus also differ between the two. The length of the mesophallus and its sclerite is greater in the new species, the apical section of the basiphallus is narrower, and the distiphallus is directed distally (not dorsally) and wider apically.

The only Nearctic agromyzid previously reared from leaf mines on Celtis   is Agromyza varifrons   , and it is unclear how its mines differ from those of A. fission   , if at all. Spencer (1969) and Spencer & Stegmaier (1973) stated only that the larva of A. varifrons   forms a “conspicuous blotch mine”. Spencer & Steyskal (1986) illustrated the mine and referred to it as an “irregular linear blotch, most frequently following the leaf margin”. Most of the A. fission   mines we collected did not follow the leaf margin, but the shape was otherwise similar to that of the mine illustrated by Spencer & Steyskal (1986). We therefore question the reliability of the records of A. varifrons   from Quebec, Arkansas, and Mississippi that are based only on empty leaf mines ( Spencer 1969; Spencer & Steyskal 1986). Spencer & Steyskal (1986) mentioned an empty leaf mine found in Arkansas that “can scarcely be associated with A. varifrons   . It is a more regular blotch toward the center of the leaf blade and possibly represents an undescribed species.” We have found such mines, without a trace of a linear portion, on Celtis laevigata Willd.   in Florida and North Carolina and on C. occidentalis   in Connecticut, Oklahoma, and Vermont.

It is noteworthy that whereas the larvae collected in Iowa in July emerged as adults two weeks later, those collected in Wisconsin the next day, as well as those collected in Oklahoma in April, did not emerge until the following spring.


University of Iowa, Museum of Natural History


Smithsonian Institution, National Museum of Natural History