Litoleptis

Imada, Yume & Kato, Makoto, 2016, Bryophyte-feeding of Litoleptis (Diptera: Rhagionidae) with descriptions of new species from Japan, Zootaxa 4097 (1), pp. 41-58 : 54

Biology of the Japanese Litoleptis

All Japanese Litoleptis species were found to be thallus-miners of thallose liverworts belonging to Aytoniaceae and Conocephalaceae (Marchantiopsida, Marchantiophyta) growing on moist riverine slopes or cliffs in evergreen or deciduous forests ( Fig. 11 a). All Litoleptis species in Japan are univoltine, and their larval stages spanned almost eleven months, from spring till late winter. The mines were formed within photosynthetic tissue of the thalli particularly near the upper side but not in the upper epidermis, and sometimes easily were seen through the upper thallus ( Fig. 11 b). The mines were linear at first, but occasionally became radiate or marked with blotches later. The number of larvae per thallus was usually one. The larvae underwent pupation inside the mine in early spring ( Fig. 11 c). The pupal stage spanned approximately a couple of weeks and then the adults emerged, which lived for only a few days. The adult flies were inactive and their feeding behavior has not been observed so far, nevertheless their labella were well-developed ( Fig. 2 a). The adults were seldom found in the field; therefore, it was difficult to observe their behavior. We did however observe in the field a L. japonica female ovipositing at the apical-dorsal part of the thallus of their host-plant later in spring.

Each Japanese species of Litoleptis fed on only a single liverwort genus as their host-plant: L. japonica feed on Conocephalum , L. asterellaphile on Asterella , and the other four species on Reboulia . Among the host-plants of the Japanese Litoleptis , Conocephalum conicum species complex and Reboulia hemisphaerica are common in Japan, whereas Asterella odora is extremely rare and whose distribution is restricted in the Kanto Region ( Iwatsuki 2001).

In general, the Japanese Litoleptis species appeared to be locally distributed in limited area except for L. japonica , nevertheless the mines of Litoleptis spp. were found relatively frequently in each population. In Japan, the association between liverworts and Litoleptis spp. seemed to be as common as it is in Micropterigidae , the most basal moth family ( Kristensen 1984). The micropterigid moths in Japan feed on liverworts and collectively have a wide distribution in Japan ( Imada et al. 2011). In particular, all the Japan endemic species of Micropterigidae belonging to four endemic genera, feed only on Conocephalum liverworts ( Imada et al. 2011). The distribution pattern of these micropterigid species in Japan, which is local and allopatric ( Imada et al. 2011), is in contrast to that of Litolepis japonica , which is widespread and covers the main islands of Japan (Hokkaido, Honshu, Shikoku, Kyushu), even though these two lineages share the same host-plant species.

Figures

FIGURE 2. Morphological features of Litoleptis applied in this study. (a) General appearance of adult of L. japonica sp. n. in lateral view, (b) head of adult male of L. japonica sp. n. in anterior view, (c) head of adult male of L. kiiensis sp. n. in anterior view, (d) female genitalia in dorsal view. (e) ventrolateral process of female of L. kiiensis sp. n. in lateral view. Abbreviations: anatg, anatergite; anepm, anepimeron; anepst, anepisternum; fc, face; gn, gena; hlt, halter; kepst, katepisternum; ktg, katatergite; lbl, labellum; mr, meron; oc, ocellar; pgn, postgena; plp, palpus; pprn lb, postpronotal lobe; prepm, proepimeron; prepst, proepisternum; sctl, scutellum; vl proc, ventrolateral process.

FIGURE 11. Habits of Japanese Litoleptis. (a) Typical habitat of Litoleptis japonica sp. n. at Nanataki in Wakayama Pref., (b) adult female of L. japonica sp. n. at Kakuma-onsen in Nagano Pref., (c) cross section of a thallus of Conocephalum conicum, in which a larva of L. japonica sp. n. mined. (d) larva of Litoleptis japonica sp. n., (e) pupa of Litoleptis japonica sp. n. (white arrow), (f) larva of Litoleptis kiiensis sp. n., (g) mines of L. himukaensis (black arrows) (h) pupa of L. asterellaphile (white arrows).