Lucilia Robineau-Desvoidy

Genus Lucilia Robineau-Desvoidy

There are four genera in this subfamily but this is the only genus in the New World.

Diagnosis. Ground color shining green, blue, or bronze, though one species, L. problematica Johnson is duller colored; suprasquamal ridge posteriorly with a shining sclerite with a cluster of setae; lower calypter bare.

Discussion. In the West Indies there are 10 species of Lucilia known, five of which are endemic to the region. Most published accounts on this genus in the Neotropical Region use the synonym Phaenicia Robineau-Desvoidy, 1863. Lucilia throughout the West Indies can be difficult to identify to species, especially the eight species with two postsutural acrostichal setae that have few distinguishing characters. Specimens are often in poor condition so a subtle character like color can be difficult to interpret. Characters used include color of basicosta and calypter and patterns of microtomentum on abdominal tergites. The distribution of tibial setae is somewhat variable and cannot be relied upon to separate species. The shape of male genitalia tends to be similar among species in this group and is of minimal value to distinguish most Lucilia in this area. The ovipositors from species in this group also exhibit little variation between species.

Six little known species were selected to study in detail, comprising L. cluvia, L. eximia, L. fayeae, L. lucigerens, L. retroversa, and L. rica; the latter four known only from the West Indies. For convenience, they are referred to as the L. eximia group. In five of the species, the male genitalia, including the epandrium, surstyli, and cerci are densely covered with long curly setae. Only L. cluvia has somewhat sparser setae on the male genitalia. The setae are often so dense that it can be difficult to see the surstylus and cercus clearly when they are drawn down in the specimen making it necessary to perform a dissection. The surstylus tends to be digitate, though it is broader and usually sharply turned inward in L. retroversa (Fig. 49). Female specimens are even more difficult to distinguish; those in poor condition may be unidentifiable.

Figures and descriptions of the phallus and other male characters and ovipositors for six species of the L. eximia group which occur in the West Indies are given. They are surprisingly uniform in appearance so shared characters are discussed here and not repeated under each species.

Male genitalia. The phallus appears to be the same general type for each species; see Fig. 56 for terms. They are closest to the “ L. caesar type ” as described by Rognes (1991). Epiphallus originates toward the anterior end of the basiphallus. Paraphallus long and slender and apically curved down with dentate tips. Hypophallus has low dentate ridges and no projections. Acrophallus long and slender ending in a dentate covered tip. No lateral ducts evident. Pregonite slender, with three setae, the distal seta in the apical position; postgonite has a single basal seta. Ejaculatory sclerite small and slender with a flattened expansion at the end, as in Fig. 64.

Variation in surstyli. In the process of describing two new species of Lucilia (L. lucigerens and L. retroversa) from the West Indies, James (1971) identified a character he described as “geniculate outer forceps.” In this condition, surstyli curve sharply inward midway to about a 90° angle similar to the condition shown in Fig. 49. When this study was begun, this character was observed in specimens of other species of Lucilia in the region, including L. cluvia, L. eximia, L. fayeae and L rica. Initially it was suspected that L. cluvia -like specimens in the region belonged to a separate species from those in North America based in part on this condition. Unfortunately it proved to be highly variable within species, and the sharp bend disappeared when specimens were heated in KOH and dissected. Lucilia retroversa was more likely to retain a distinctive bend than the other species though even that was variable (Fig. 49).

I have concluded that the bend in the surstyli is not useful for species distinctions because it is too variable and probably caused by environmental factors. In hot, humid climates, many collected specimens of Lucilia are very moist and often appear teneral. I suspect that the drying process in recently killed specimens can sometimes lead to the warping of the surstyli. I also observed this condition in some specimens of Lucilia from the Florida Keys and Central America.

Female genitalia. Ovipositors in the L. eximia group are composed of three segments, 6, 7 and 8. T6 is one complete sclerite, while T7 and T8 are more or less divided; sternites are single sclerites. Epiproct, hypoproct and cerci similar in all six species; see Fig. 88 for characters and see ovipositor figures cited under each species. T6 broad, with paired spiracles and a strong row of setae on the rear margin, and no mircrotrichia on this tergite in any of the species. ST6 tends to be pear-shaped with dense setae on the rear third or more, and mircrotrichia are present on the rear portion of this sternite in all species. A dashed line on the rear of ST 6 in each figure shows how far forward the microtrichia are found. T7 separated by a membranous area that extends nearly to the rear of the tergite with a row of setae on the posterior margin. ST7 elongate, often a little longer than T7 with a row of strong setae at the rear. T8 divided into two distinct tergites, each section with strong setae posteriorly. ST8 longer than T8 with a strong row of setae posteriorly. Epiproct, cerci and hypoproct covered with setae and mircrotrichia. Intersegmental and most pleural membranes have microtrichia which are directed forward and vary in shape by segment; selected areas are shown in each figure.