Colobaea deemingi Knutson & Bratt, 2020

Bratt, Albertus D., Knutson, Lloyd V., Murphy, William L. & Daniels, Anthony A., 2020, Biology, immature stages, and systematics of snail-killing flies of the genus Colobaea (Diptera: Sciomyzidae), with overviews of aspects of the tribe Sciomyzini, Zootaxa 4840 (1), pp. 1-64 : 24

Colobaea deemingi Knutson & Bratt , n. sp.

Map 6

(BNN 7105–07, 7317–18, 7343)

This species, from Iran and Pakistan, is similar in color pattern to the African C. occidentalis , known from Niger, northern Nigeria, and Ethiopia, and to C. punctata , a widespread Palearctic species found from Ireland to Israel (northern Negev), northeastern Iran (Mazanderan), and east to Kazakhstan and eastern Siberia.

The biology and immature stages of C. deemingi are known only from progeny reared from adult flies collected by LVK in southwestern Iran (five localities near Dezful, one locality near Shooshtar) during November 1971 (FT 7110) and April 1973 (FT 7320, 7334). During November 1971, adult flies were found at only two localities, but during April 1973 they were found at six localities. Most adult flies were swept from hygrophilous grasses and Carex emerging from a few inches of water at the margins of marshes near the Persian Gulf. The 0.5–20 hectare marshes were rimmed by extensive growths of Typha angustifolia . At Boneh Javaz, 41 km SE of Dezful, in November 1971, adult flies were swept from wet, grassy areas between patches of Typha growing in unshaded, shallow depressions receiving water from a nearby irrigation channel. Adult flies were especially common at that location; in fact, during April 1973, C. deemingi was one of the most abundant species of flies at a site in Bayza, 610 km SE of Dezful. No C. deemingi were collected in a Malaise trap placed where adult flies had been collected with a sweep net during November 1971 at Boneh Sayyed Moosa, 16 km W of Dezful. No larvae or puparia of C. deemingi have been found in nature.

For detailed descriptions of typical aquatic habitats in southwestern Iran, with discussion of the ecology of freshwater snails, see Chu et al. (1968).

Other species of Sciomyzidae found with C. deemingi in Iran and Pakistan included Ditaeniella grisescens (Meigen) , Hydromya dorsalis (Fabricius) , Ilione turcestanica (Hendel) , Pherbellia cinerella (Fallén) , P. fuscipes (Macquart) , Sepedon sphegea (Fabricius) , and S. spinipes (Scopoli) . Aquatic snails present at the collecting sites included Bulinus truncatus (Audouin) , Gyraulus intermixtus (Mousson) , Melanoides tuberculata (O.F. Müller) , Planorbis planorbis , and Radix gedrosiana (Say) .

Adult flies collected on 4 November 1971 mated the same day and continued to mate until 14 November; adult flies collected on 16 April 1973 were observed mating between 17 and 29 April; and a pair of adult flies were collected in copula on 25 April. In the laboratory, adult flies that emerged between 25 and 28 November first mated eight days later and produced viable eggs during December 1971 and January 1972. Adult flies collected 16 April 1973 were first seen to oviposit on 21 April. Females scattered eggs over the damp moss or cotton in the bottom of the breeding jar and did not oviposit on a living snail. The incubation period was about 48 hours.

Larvae killed and consumed G. intermixtus of 2.5–6.5 mm in greatest diameter. Mature larvae also killed and fed on Radix gedrosiana of about 4.0 mm in length, but first-instar larvae did not attack small Lymnaea sp. or Helisoma trivolvis . Each larva consumed one or two G. intermixtus or R. gedrosiana . The larval feeding behavior was very similar to that of C. punctata . Several larvae often fed together in a single snail. They continued to feed on black, putrid tissues long after the snail prey had died. The total duration of larval life was 8–10 days.

Puparia were formed in shells of G. intermixtus and occasionally in shells of R. gedrosiana . Pupariating larvae produced a mass of frothy septum material in the aperture of the shell. In Iran, larvae pupariated between 13 November and 16 December 1971 and between 23 April and 3 May 1973. Twenty-five adult flies emerged between 25 November and 8 December 1971, and many more emerged between 5 and 15 May 1973. A complete second generation was not reared from these adult flies because of the authors’ travel requirements. The puparial period lasted about 12 days. The total duration of the immature stages was 22–24 days.

Figures

MAP 6. Geographic range of Colobaea deemingi Knutson & Bratt (this paper).