The following key is detailed and functions also as a diagnosis for each species. More detailed descriptions of L. silvarum and L. elongata were given by Hall (1948) and a more detailed description of L. bufonivora was given by Rognes (1991).The three species can be separated from other North American species of Lucilia by the following combination of character states: 1) brown or black clavate palpus (vs. yellow or orange palpus in L. sericata, L. cuprina, L. thatuna, L. coeruleiviridis Macquart, 1855, L. cluvia (Walker, 1849), L. mexicana Macquart, 1844, L. eximia (Wiedemann, 1819) and L. illustris (Meigen, 1826)); 2) length of head at level of lunule more than half height of head (a state shared also by L. magnicornis (Siebke, 1863), L. thatuna and some L. sericata; in L. cuprina, some L. sericata, L. coeruleiviridis, L. cluvia, L. mexicana and L. eximia, head length at level of lunule less than half head height); 3) first flagellomere less than half eye length in profile and arista normal, with hairs erect and longer than width of first flagellomere (in L. magnicornis, first flagellomere longer, more than half eye length in profile and arista with short setae, usually much shorter than width of first flagellomere); 4) T 3 with one or two pairs of long, erect median marginal setae (a state shared by L. magnicornis and males of L. thatuna; in other North American Lucilia species, median marginals not strong or erect); 5) basicosta dark brown or black (L. sericata, L. cuprina, L. thatuna, L. coeruleiviridis and L. cluvia have yellow basicosta); 6) subcostal sclerite pubescent (a state shared by all other North American Lucilia species except L. illustris which has a setose subcostal sclerite) (Hall 1948; Shewell 1987; Rognes 1991; Whitworth 2006); and 7) aedeagus of L. bufonivora type (Rognes 1991, for L. bufonivora and L. silvarum; this study, for the three species). Male and female head, presutural area of the notum, male abdominal sternites, and the terminalia of both sexes of L. silvarum, L. bufonivora, and L. elongata are shown in Figs 1–6, 9– 14, 16–48.
1. Distance between rearmost presutural acrostichal setae equal to (in most specimens examined) (Fig. 9) or slightly less than distance between rearmost presutural acrostichal and dorsocentral setae in rear row; usually with three postsutural acrostichal setae on each side; upper calypter pale and lower calypter tan in male, upper and lower calypters pale in female. Male: Frons, at narrowest, 0.07 (0.06–0.09/ 8) of head width (Fig. 1); discal setae on T 5 only; ST 5 normal (Fig. 12); cercus with apical hook in profile, surstylus long and slender with apical half evenly tapering in profile (Fig. 16). Female: Frons, at narrowest, 0.33 (0.32–0.37/ 8) of head width and about as wide as eye when seen from above, frontal vitta widened towards vertex (Fig. 2); T 7 almost completely divided; cercus normal in shape (lobate); epiproct without microtrichia (Fig. 40); ST 7 narrow apically; ST 8 long and rectangular in shape (Fig. 41)......................................................... Lucilia silvarum
- Distance between rearmost presutural acrostichal setae distinctly less than (in most specimens examined) (Figs 10, 11) or almost equal to distance between presutural acrostichal and dorsocentral setae in rear row; number of postsutural acrostichal
setae variable (2–3); upper and lower calypters pale in both sexes (in a few male specimens, lower calypter with a small tan area close to inner edge). Male: Frons 0.09–0.16 of head width (Figs 3, 5); discal setae, in addition to T 5, usually present on T 3 and T 4 (as in L. bufonivora) or on T 4 only (as in L. elongata); ST 5 normal or prominent (larger and longer); cercus without apical hook, surstylus broad and apically blunt (Figs 21, 26). Female: Frons 0.30–0.37 of head width (Figs 4, 6); T 7 completely divided; cercus normal (lobate) or elongate; epiproct without or without microtrichia (Figs 42, 44); ST 7 not as above; ST 8 small and shaped as in ST 7 or its distal part almost a circle (Figs 43, 45).......................................... 2 2. Male: Frons 0.094 (0.09–0.10/ 7) of head width (Fig. 3); abdomen normal, not conspicuously elongated; T 3 (see comments below) and T 4 usually with 1–5 strong discal setae; ST 5 normal, shorter than T 5 (Fig. 13); surstylus parallel-sided in profile with a blunt tip (Fig. 21). Female: Frons narrower, at narrowest, 0.30 (0.30–0.31/ 7) of head width and narrower than eye when seen from above, frontal vitta parallel-sided (Fig. 4); cercus elongate (narrow); epiproct with microtrichia (Fig. 42); ST 7 shaped distally as broad semi-circle; ST 8 with distal part shaped as a semi-circle (Fig. 43)............ Lucilia bufonivora
- Male: Frons wider, at narrowest, 0.13 (0.12–0.16/ 11) of head width (Fig. 5); abdomen distinctly elongated; T 3 without discal setae; T 4 with discal setae in some specimens; ST 5 larger and as long as T 5 (Fig. 14); surstylus with a straight upper edge and a lower rounded edge, tip slightly upturned in profile (Fig. 26). Female: frons wider, at narrowest, 0.35 (0.32–0.37/ 6) of head width and about as wide as eye when seen from above, frontal vitta widened towards vertex (Fig. 6); cercus normal (lobate); epiproct without microtrichia (Fig. 44); ST 7 distally constricted then dilated with a median process; ST 8 with distal part almost a circle (Fig. 45).......................................................................... Lucilia elongata