Tropicomyia Spencer, 1973
This genus belongs to the Ophiomyia-group (Tribe Ophiomyiini). Initially Tropicomyia was erected in order to separate the stem-mining Genus Melanagromyza from a group of leaf-mining species. After removing some species now belonging to the Genus Kleinschmidtimyia (Spencer, 1986), Tropicomyia can be regarded as a monophyletic group (but see the taxonomic appendix of Spencer, 1990). Accordingly, the monophyly can be confirmed by larval adaptations to the leaf-mining feeding habit. The strongest argument for the monophyly can be found in the fine larval mouthhooks, while other characters strongly resemble the other genera of the Ophiomyiini, especially Melanagromyza.
Larval and pupal characters
The mandibles are situated on the top of each other, both have a serrated edge at the apical part instead of the usual mouth hooks tropicomyia ceph2.pct. Among Agromyzidae this unique character can be interpreted as adaptation to epidermal leaf-mining behaviour.
Dorsal sclerites above the mandibular complex are normally elongated tropicomyia ceph.pct.
Other larval characters: Posterior spiracles normally with the primitive condition of three bulbs each Tropicomyia Puparium Hst.pct.
Puparium: Both posterior spiracles together situated on a protuberance Tropicomyia Puparium.pct.
The caudal parts of the cephalopharyngeal skeleton closely resemble Ophiomyia tropicomyia ceph.pct: Dorsal bridge is missing; upper and lower part of the dorsal arm of the basal part are long and of equal thickness.
A broad frontal process just above the facial mask is often but not always present. This structure is neither homologous nor even similar to the filament-like frontal processes found in Phytomyza. A similarity is only apparent by a strict side view. The processes of Ophiomyia and Tropicomyia are sickle-shaped when viewed from above.
Adults
The adults are usually very small and very similar to the related genera Ophiomyia and Melanagromyza. The size is normally small (wing length: 1.5 - 2.0 mm); two dorsocentral bristles, black halteres, very short genae versus large eyes, basiphallus distinctly sclerotized at margins and with sclerotized dorsal bridge (or with sclerotized frame).
Male genitalia
Side sclerites of basiphallus usually well visible, with distinct bridge. Basal vesica distinctly separated and in more basal position than two conspicuous subbasal vesicae Tr flacourtiae genitalia.pct. Frequently a single thin appendage of the distiphallus can be found. Hypandrium usually of intermediate length with hypandrial apodeme. Epandrium and gonites as in the other genera of the group Ophiomyiini.
Taxonomical remark
Many species differ only in very slight characters of the male aedeagus, identification to species level is difficult. Moreover, due to insufficient type material the status of several species is not fully clarified. Likewise, some larval characters even suggest some more unknown species.
Bionomics
In feeding on the extremely thin epidermal layers of leaves, the species belonging to Tropicomyia are unusual, highly specialized leaf miners. As illustrated above, their mouthparts are adapted to this feeding habit.
Many species exhibit an outstanding wide host range, they are truly polyphagous. Host records include among others a fern. Moreover, the only known agromyzid leaf miner on gymnosperm plants belongs to this genus (see Spencer, 1990). Normally higher population densities of or economic damage caused by Tropicomyia is rare. However, occasional outbreaks can cause some damage on cultivated plants. The main economical important host plants are tea and coffee.
Pupation always takes place within the mine, the anterior spiracles press against the upper surface of the mine.
Distribution
Basically tropical: East Palaearctis, Orientalis, Australis, Afrotropis, Madagascar.