Lucilia thatuna Shannon 1926

Lucilia thatuna Shannon, 1926

(Figs 7–8, 15, 49–59)

Lucilia thatuna Shannon, 1926: 132. Holotype male (USNM, No. 28,889). Type locality: Moscow Mountains, Idaho, USA.

Bufolucilia thatuna: James 1953: 147, 1955: 7; Hall 1965: 927.

Lucilia thatuna: Aubertin 1933: 417; Stevens & Hall 1996: 1087; Whitworth 2006: 721; McDonagh & Stevens 2011: 1761; DeBry et al. 2013: 75.

Phaenicia thatuna: Hall 1948: 269.

Lucilia thatuna is an uncommon western North American species, which has been collected from California, Colorado, Idaho, Oregon, Utah, Wyoming, and Washington (Whitworth 2006, see also Appendix 1). The biology of this species remains unknown (Hall 1948), however it likely parasitizes anurans, since it is usually collected in areas around marshes and streams (T. Whitworth, unpublished data).

Lucilia thatuna has the same head proportions as the three species of the L. bufonivora species group. However, it has a yellow palpus and basicosta and only the male possesses long, erect median marginal setae on T3 (Whitworth 2006). Lucilia thatuna can be easily separated from other species of Lucilia occuring in North America by the key of Whitworth (2006).

In this study, L. thatuna was found to possess an aedeagus (Figs 51–53) of the L. sericata type based on the following synapomorphies stated by Rognes (1991): ventral plate large; paraphallus hook-shaped, abruptly turned downwards apically and serrated apically on dorsal side; hypophallus shaped as low dentate ridges; apically the hypophallus forms a peculiar vertical passage with a posterior and lateral wall guiding the movement of the tip of the paraphallus; acrophallus short with lateral ducts. Therefore, L. thatuna correctly belongs to the L. sericata (Meigen, 1826) species group which includes other species such as L. cuprina (Wiedemann, 1830), L. regalis (Meigen, 1826) and L. richardsi Collin, 1926.

Hall (1948) was the first to mention that L. thatuna is related to L. sericata. Stevens & Hall (1996) grouped L. thatuna with L. sericata, L. cuprina, L. pilosiventris Kramer, 1910, L. regalis and L. richardsi based on the yellow colour of the basicosta. Molecular phylogenetic studies clearly show that L. thatuna is not related to L. silvarum, L. bufonivora or L. elongata (McDonagh & Stevens 2011; DeBry et al. 2013). If it is found for certain that L. thatuna parasitizes anurans, then anuran parasitic habit has evolved at least twice in the genus Lucilia.

Diagnosis. Both sexes: Specimens often bluish, which separates them from the green or coppery L. sericata or the coppery L. cuprina. First flagellomere broader than width of parafacial at level of lunule, often cupped inward, inner margin often reddish, especially in female (Figs 7, 8). Palpus and basicosta yellow to orange. Three postsutural acrostichals.

Male: Frons 0.05 (0.044–0.058/12) of head width, with frontal plates almost touching (Fig. 7), frons width is much narrower than in L. cuprina or L. sericata. ST1–ST5 as in Fig. 15. T3 with strong median marginal setae. Cercus, in profile, narrow with a blunt tip, distal half of inner edge slightly and smoothly curved posteriorly (Fig. 49). Surstylus digitate in profile. Aedeagus of L. sericata type (Figs 51–53). Paraphallus with a characteristic bifid tip (Fig. 52) which is not found in any other Lucilia species described by Rognes (1991). Pre- and postgonites as in Fig. 54. Bacilliform sclerites with the membrane between them with a characteristic V-shaped cleft (Fig. 55). Ejaculatory sclerite as in Fig. 56.

Female: Frons 0.28 (0.27–0.36/10) of head width (Fig. 8). T7 divided proximally to nearly half its length (Fig. 57). T8 divided distally to nearly half its length. Cercus lobate and epiproct non-microtrichose. ST7 narrowed distally (Fig. 58). ST8 shaped as in L. silvarum but with the distal end straighter. Spermathecae as in Fig. 59.

Description. See Hall (1948).