Dentifibula Felt, 1908

Gagné, Raymond J. & Bertone, Matthew A., 2022, Redescription of Dentifibula viburni (Felt) (Diptera: Cecidomyiidae) and review of the genus, Zootaxa 5175 (5), pp. 583-592 : 584

Dentifibula Felt

Dentifibula Felt 1908: 385 , 389 (type species, Cecidomyia viburni Felt , original designation).

Muirodiplosis Grover 1965: 111 (type species, spinosa Grover (original designation); Gagné 1973a: 500 (junior synonym of Dentifibula ).

Diagnosis. Dentifibula belongs to the Lestodiplosini whose larvae are predaceous on various insects and mites ( Gagné & Jaschhof 2021). A key to genera can be found in Gagné (2018). Only two characters separate adults of this genus from the more speciose and diverse Lestodiplosis . The first difference is the prominent conical extension in Dentifibula of the gonocoxites beyond the insertion of the gonostylus ( Figs 6–7 ); the second is the presence of only two circumfila instead of three on each of the male flagellomeres ( Fig. 3 ). This second character is not exclusive because an undescribed species of Dentifibula from Australia is known with three circumfila on each flagellomere ( Kolesik & De Faveri 2014) and a few Lestodiplosis spp , are known with two or an incomplete third ( Harris 1968). The single distinctive character of the gonocoxite may seem a minor difference on which to base a genus but there is no reason to believe it arose more than once. The only two well-known species, D. viburni and Dentifibula nigroapicalis Kolesik (in Kolesik & De Faveri 2014), show distinctive dark spots on the wing and light- and dark-banded legs, so possibly all the other species do also. This has not been noted in the other species because the dark scales responsible for the marks are lost in slide preparations. Felt (1907, 1908, 1918) did not mention maculations on D. viburni because he probably saw his specimens only on slides after preparation by an assistant. Felt incorrectly described the palpi of his three manifestations of D. viburni (and later of his two Sri Lankan species) as having three segments. He used this to characterize his genus, but the palpi of his Dentifibula species are actually four-segmented. The first palpal segment in these species is short and usually partially hidden, but always has a telltale seta or setae, marking it as a true segment and not the palpiger ( Fig. 5 ).

Larvae are known of only two species, D. viburni and D. nigroapicalis . Those of D. viburni could pass for any Lestodiplosis with their robust head, very long antennae, ventral pseudopods and dorsal anus. The arrangement of the papillae is particularly diagnostic for the lateral and sternal papillae ( Figs 12–13 ). Kolesik & De Faveri (2014), while showing in photographs and drawings what otherwise resembles a Dentifibula / Lestodiplosis , describe their larva as having a ventral anus and lacking pseudopods. Kolesik (pers. comm., V-28-2022) wrote that the single slide-mounted larval specimen in his series of D. nigroapicalis is a tiny, poor specimen that does not allow certainty about those characters. Kolesik & De Faveri (2014) also noted the lack of a sternal spatula on their species, but the larva is so small it might be a second instar that would normally lack that organ.

We note here an exclusive larval feature of both Dentifibula and Lestodiplosis : Two sternal papillae are evident on the prothorax and four on the eighth abdominal segment but are missing on the remaining segments ( Fig. 12 ). To account for the missing sternal papillae, Möhn (1955) suggested that sternal papillae of Lestodiplosis were transformed into pseudopods in the remaining thoracic and abdominal segments. This might account for the pair of pseudopods on the meso- and metathorax, but does not explain how in the first through seventh abdominal segments there are only three pseudopods in place of the erstwhile four sternal papillae. If Möhn’s hypothesis is correct, the middle of three abdominal pseudopods, placed along the horizontal line where the sternal papillae would be, might have subsumed two of the erstwhile four sternal papillae.

Figures

FIGURES 3–9. Dentifibula viburni. 3, Male fourth flagellomere (ventral). 4, Female fourth flagellomere (ventral). 5, Head with detail of palpus (frontal). 6, Male terminalia (dorsal). 7, Same (ventral). 8, Same (sagittal). 9, Terminus of ovipositor (lateroventral). Figures 10–11, Visible details of terminalia of uncleared types. 10, Dentifibula ceylanica. 11, Dentifibula obusilobae.

FIGURES 12–15. Dentifibula viburni. 12, Third instar, anterior segments (ventrolateral). 13, Same, first thoracic segment (dorsolateral). 14, Same, terminal segment (ventral). 15, Pupa, anterior segments (ventral).