Liriomyza cf. taraxaci Hering, 1927

Eiseman, Charles S. & Lonsdale, Owen, 2019, New State and Host Records for Agromyzidae (Diptera) in the United States, with the Description of Ten New Species, Zootaxa 4661 (1), pp. 1-39 : 15-16

Liriomyza cf. taraxaci Hering

( Fig. 49 )

Material examined. MASSACHUSETTS: Franklin Co., Northfield, Old Wendell Rd. (42.654294, -72.428336), 12.vii.2017, em. by 31.vii.2017, C.S. Eiseman, ex Lactuca biennis , #CSE4039, CNC 939691 (1³); NORTH CAR- OLINA: Durham Co., Durham, Pelham Road, 28.iv.2017, em. 21–23.v.2017, T.S. Feldman, ex Lactuca canadensis , #CSE3701, CNC 939814–939819 (3³ 3♀); 10.vi.2017, em. 26–30.vi.2017, T.S. Feldman, ex Lactuca canadensis , #CSE3861, CNC 939785–939797 (4³ 9♀).

Hosts. Asteraceae : Lactuca * biennis (Moench) Fernald, L. * canadensis L. , L. sativa L., Taraxacum officinale F.H. Wigg. ( Eiseman & Lonsdale 2018; see Comments below). In Washington, E. Stansbury (in litt.) has photographed mines on L. serriola L. consistent with the other Lactuca mines discussed below. Spencer (1969) reported Cichorium intybus L. as a host for Liriomyza taraxaci based on empty leaf mines.

Leaf mine. ( Fig. 49 ) Upper surface; on Taraxacum , a rapidly widening serpentine mine, centrally suffused with brown, expanding into a whitish blotch, with frass in sparsely scattered black grains. The mine of an unconfirmed female specimen on this host had conspicuous feeding lines in the blotch but was otherwise identical ( Eiseman & Lonsdale 2018). The mine on Lactuca sp. illustrated by Scheffer & Lonsdale (2018) is a blotch with no evident serpentine portion. Our North Carolina specimens were reared from large blotch mines on L. canadensis containing multiple larvae. We have found similar communal mines on L. biennis in Massachusetts, with six or more larvae feeding together, although our single specimen may have been reared from a solitary larva (photographs from the collection date show one mine containing a single larva and one containing three). The frass is mostly in small grains, with some larger lumps and strips. The mines on L. biennis and L. canadensis exhibit secondary feeding lines as with that of the female from Taraxacum . In one photograph of aggregate mines on L. biennis , numerous initial serpentine portions are evident; it is possible that all mines on Lactuca begin with this feature but it is obliterated by the later blotch.

Puparium. Yellow to yellow-orange; formed outside the mine.

Distribution. USA: AK, IL, MA, * NC, NY, WA, WI (leaf mines only); Canada: AB, BC, MB, NB, ON, QC, SK, YT; Europe ( Eiseman & Lonsdale 2018).

Comments. The specimens listed here belong to what Lonsdale (2017) diagnosed as Liriomyza taraxaci , noting that this species is likely a complex of Asteraceae-feeders that require further study. There are slight differences in the genitalia compared to the “typical” Taraxacum feeders and other specimens reared from Lactuca that do not allow for confident association. Lonsdale (2017) tentatively assigned to L. taraxaci specimens reared from Lactuca sativa in Washington. These had been identified as Liriomyza endiviae Hering by Spencer & Steyskal (1986), whose only other basis for reporting that species from North America was empty leaf mines found on Lactuca in Maryland; those mines may likewise have been made by L. taraxaci s.l. Scheffer & Lonsdale (2018) reported a fly reared from a blotch mine on Lactuca sp. in New York as L. taraxaci without qualification.

The tendency for larvae to form aggregate /communal mines on Lactuca spp. may be attributable simply to females responding to the much larger leaves on these hosts by laying multiple eggs per leaf, rather than being indicative of distinct species with different habits.

Figures

FIGURES 46–56. leaf mines: 46: Liriomyza garryae spec. nov., on Garrya ovata; 47: same; 48: L. phloxiphaga spec. nov., on Phlox paniculata; 49: Liriomyza cf. taraxaci Hering, on Lactuca biennis (mine containing at least three larvae); 50: L. cf. trixivora Lonsdale, puparium in mine; 51: L. cf. trixivora, on Trixis californica; 52: L. virgo (Zetterstedt), on Equisetum fluviatile; 53: L. zinniae Spencer, on Encelia farinosa; 54: same, puparium in lower surface blister; 55: Liriomyza sp. 1, on Chaetopappa bellidifolia (young mine); 56: same (complete and vacated mine).