Dichotomous table for gallers on Inula

(incl. Dittrichia, Limbarda)

by Hans Roskam

1a On above-ground or subterranean shoot parts => 2

1b Roots with many small tuberous swellings. I. brittannica: Meloidogyne hapla

1c Unilocular, round, lignified gall, up to 3 mm in diameter. The young gall is green, later it turns yellow to brown. Pupation, after hibernation, in the gall. I. hirta: Isocolus brunneus

2a On capitula => 15

2b On vegetative plant parts => 3

3a On single, or several, usually disfigured terminal leaves => 12

3b On stems, shoot tips; malformations sometimes extending into isolated leaves => 4

4a On shoot tips or lateral buds => 5

4b Smooth soft-walled globular gall, about 5 mm across, yellow-green to red, on various places on stem, leaf buds and flower heads; sometimes several clustered together or connate. One chamber with one larva. Dittrichia viscosa; Inula britannica, conyzae, ensifolia, oculus-christi, salicina: Acodiplosis inulae

4c Spindle-shaped green gall (20 x 10 mm), sometimes spherical; large cavity containing a milk-white larva. Adults emerge in end May. Limbarda crithmoides: Euarestella megacephala

4d Spindle-shaped galls on stem base and in stems, contain frass: Unidentified lepidopteran

4e Unilocular, round, lignified gall, up to 3 mm in diameter. The young gall is green, later it turns yellow to brown. Pupation, after hibernation, in the gall. I. hirta: Isocolus brunneus

5a Malformations of above-ground buds or shoot tips => 6

5b The subterranean buds, and, sometimes also basal above-ground buds on root collar transformed to one-chambered solitary or clustered galls, up to 5 mm long, tough-walled, fleshy; the outside with dense, long, initially white, later grey-brown felt-like hairs. One reddish larva. I. britannica, ensifolia, germanica, hirta, hybrida, salicina: Inulomyia subterranea

6a Terminal- or lateral artichoke-like buds, malformations remaining closed => 7

6b Terminal buds or buds on stems, sometimes involving the neighbouring leaves, transformed into a one-chambered dry-fleshy closed gall about 5 mm across. Containing a single larva. Dittrichia viscosa; Inula britannica, conyzae, ensifolia, oculus-christi, salicina: Acodiplosis inulae

7a Rosette-like malformations => 11

7b More or less bud-like malformations => 8

8a Galls not exceeding 10 mm => 9

8b Partly open bud or young leaves, usually of basal rosette, are largely stunted and densely haired over an extensive area; containing yellow-orange larvae. I. conyzae: Neomikiella beckiana

9a Glabrous or pubescent galls caused by midge larvae => 10

9b Leaves at the shoot tip stunted, curled. In the middle bud-like converging; the following leaves slightly increasing in size and ± rosette-like spreading. I. salicina: Unidentified gall mite

10a Galls conspicuously pubescent => 11

10b Galls inconspicuously pubescent. Young leaves terminally ± severely stunted, at least the basal parts pale and rolled together composing a slender, erect artichoke, enclosing the youngest parts. Containing whitish to yellow larvae. I. britannica, hirta, salicina: Contarinia inulicola

= In galls on terminal shoots, or lateral buds, of various Inula species from dry habitats live gall midges belonging to a second species group, which may differ from the species on I. britannica.

11a Gall about 4–10 mm long, sometimes enclosed by a few shortened leaves, basally thickened and widened, with their leaf blade ± spreading => 13

11b Gall ± distinctly bud-like, about 8–18 (20) mm long; the exterior leaves decreasingly stunted, the base conspicuously enlarged and variously disfigured, strongly white pubescent over large areas. Larva yellowish-red. I. conyzae: Neomikiella beckiana

12a Malformations caused by aphids or cercopids, always lacking dense pubescence => 13

12b Leaves on the shoot tip ± tightly rolled or folded together, densely pubescent and partially stunted. I. salicina, Dittrichia viscosa: Eriophyes cupulariae

13a Aphid galls => 14

13b Leaf blades downward arched and strongly curled, dark green close to the froth-covered nymph. I. britannica, helenium: Philaenus spumarius

14a Leaf blade disfigured, deflected, yellow-spotted, with disfigured venation. Dittrichia viscosa, I. conyzae, helenium: Brachycaudus helichrysi

14b Leaf blade with loose upward marginal roll, sometimes narrowly pod-like malformation on young leaf blades. I. ensifolia, hirta, salicina: Brachycaudus salicinae

15a Larvae rotund-cylindrical usually living, in the soon ± hardened, upwardly arched receptacle. Tephritid gall causers => 16

15b More or less expanded parts of the receptacle of younger, strongly transformed capitula almost semiglobular. Galls about 4–5 mm long with soft fleshy wall containing an elongate midge larva. Dittrichia viscosa; Inula britannica, conyzae, ensifolia, oculus-christi, salicina: Acodiplosis inulae

15c Midge larvae develop in flower heads. I. salicina: Jaapiella inulicola

15d Unilocular, round, lignified gall, up to 3 mm in diameter. The young gall is green, later it turns yellow to brown. Pupation, after hibernation, in the gall. I. hirta: Isocolus brunneus

16a Separate galls with tough, later woody wall; mostly with several in a flower head and bulging out from the receptacle => 17

16b Receptacle sometimes thickened on one side. Galls tough-walled when mature, but not woody. I. britannica, ensifolia, hirta, oculus-christi: Inuromaesa maura

16c Inducer of hardened receptacle galls on I. britannica, conyzae: Trupanea stellata

17a Receptacle inside the flower head strongly swollen, bulge-like to conical disfiguration, apically eventually having an emergence hole. One larva per chamber. I. ensifolia hirta, hybrida, salicina, Limbarda crithmoides: Myopites eximia and/or M. longirostris

17b Similar galls on I. britannica: Myopites tenellus and/or Inuromaesa maura

17c On Dittrichia viscosa. Receptacle swollen, transformed into a woody multilocular gall, red-brown, rotund or elongated, glabrous, measuring 4–8 mm with apically 2–4 (5–6) paler coloured appendages representing the achenes. Each larval chamber containing a white-yellowish larva: Myopites limbardae and/or M. olivieri

17d On Dittrichia viscosa. The receptaculum is transformed into a smooth sphere; a few galled achenes, crowned by pappus hairs emerge as narrow cones from the gall; the other achenes are aborted and are arranged around the gall: Myopites stylatus

= Myopites inulaedysentericae, occasionally recorded from Inula species

= Furthermore from flower heads have been recorded the tephritid flies Ictericodes zelleri from I. conyzae, and Acinia biflexa from I. brittanica

mod 20.iii.2020