Key to Third-Instar Chrysomyinae (Diptera: Calliphoridae) from ...

Key to Third-Instar Chrysomyinae (Diptera: Calliphoridae) from Carrion in the Continental United States JEFFREY D. WELLS, JASON H. BYRD,1

AND

TAREK I. TANTAWI2

Department of Justice Sciences, University of Alabama at Birmingham, 901 South 15th Street, Birmingham, AL 35294Ð2060

J. Med. Entomol. 36(5): 638Ð641 (1999)

ABSTRACT The introduction of 4 Chrysomya Robineau-Desvoidy spp. to the Americas has made obsolete previously published keys to Nearctic calliphorid larvae, particularly those covering the subfamily Chrysomyinae. To assist forensic entomologists, ecologists, and public health workers, we provide a key to 3rd instars of 8 chrysomyine species reported from or likely to occur in carrion within the continental United States. The rare (in the United States) species Cochliomyia aldrichi Del Ponte, C. minima Shannon, and Chloroprocta idioidea (Robineau-Desvoidy) are not included because specimens and suitable descriptions were unavailable. KEY WORDS blow ßy, maggot, forensic entomology, larval morphology, invasion

ANY INVESTIGATION OF carrion arthropods in North America now must consider 4 new blow ßies. These members of the Old World genus Chrysomya Robineau-Desvoidy recently have become widespread in the Americas (Baumgartner and Greenberg 1984) and 2, C. rufifacies (Macquart) and C. megacephala (F.), have become established in the contiguous United States (Olsen and Sidebottom 1990, Wells 1991, Baumgartner 1993, Martin et al. 1997). The other 2 species, C. albiceps (Wiedemann) and C. chloropyga (Wiedemann) (⫽C. putoria), may be here soon. Although C. albiceps has not been reported in the New World outside of South America, the similar appearance of this species to C. rufifacies would make it difÞcult to monitor if it were spreading north through Central America, a region already occupied by the latter species (Baumgartner and Greenberg 1984). Almost certainly there is no climatic barrier to keep C. albiceps from reaching a large portion of the United States. In Europe, C. albiceps larvae have been recorded as far North as Zurich, Switzerland (Rognes 1997). The previous range of C. chloropyga spans the length of Africa (Schumann 1986). Along with C. albiceps and C. megacephala, this species entered this hemisphere via southern Brazil, and it has since spread at least as far north as Panama (see Materials and Methods). This species has the potential to seasonally invade the United States. Adults of these invaders may be separated from the native U.S. fauna using the keys of Hall (1948) and Dear (1985) (readers who rely on HallÕs monograph should consult Dear for nomenclature changes), but the information needed to recognize the larval forms 1 Department of Entomology and Nematology, University of Florida, Gainesville, FL 32611Ð 0620. 2 Department of Zoology, Faculty of Science, Alexandria University, Moharrem Bey, Alexandria, Egypt.

is scattered widely. Forensic entomologists, ecologists, and public health workers in the United States need a single publication that separates the larvae of these species from native members of the same subfamily, Chrysomyinae (calliphorid larvae with an incomplete peritreme, Fig. 1). We present herein a key to the 3rd instars of the common carrion-feeding Chrysomyinae now known, or likely to occur, in carrion in the continental United States. Three species, Cochliomyia aldrichi Del Ponte, C. minima Shannon, and Chloroprocta idioidea (Robineau-Desvoidy), were not included because neither specimens nor suitable descriptions were available. The Þrst 2 apparently are rare in the continental United States, and C. idioidea is unlikely to be collected in this country far from the coast of southern Texas (Hall 1948). All other Chrysomyinae in this region are obligate parasites, and their immature stages should not be found in carrion (Hall 1948, Sabrosky et al. 1989). Materials and Methods Third instars of the following species were examined. Cochliomyia macellaria (F.) from a laboratory colony established from Kerr County, TX, USA, and others reared from adults collected in San Ramon, Peru; Phormia regina (Meigen) from a laboratory colony established with individuals from Chicago, IL, and wild larvae from Sonoma County, CA, USA; Protophormia terraenovae (Robineau-Desvoidy) from a laboratory colony established from Pullman, WA, USA; Compsomyiops callipes (Bigot) [⫽Paraluclia wheelri (Hough)] collected from Santa Clara, CA, USA; Chrysomya albiceps from Alexandria, Egypt, and from Campinas, Sao Paulo, Brazil; C. rufifacies from Kerr County, TX, USA, and from Okinawa, Japan; C. chloropyga reared from adults collected in San Ramon, Peru, and from Chilibre, Panama; and C. megacephala

0022-2585/99/0638Ð0641$02.00/0 䉷 1999 Entomological Society of America

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Fig. 1. Spiracular plate of C. macellaria. Arrow indicates incomplete portion of peritreme.

Fig. 2. C. albiceps.

Fig. 3. (A) C. albiceps and (B) C. rufifacies. Arrows indicate apical spines on tubercles.

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Fig. 4. Posterior dorsum of C. chloropyga showing covering of Þne setae.

collected from Laloki, Papua New Guinea, and from a laboratory colony established from the island of Oahu, HI, USA, and from Okinawa, Japan. At least 20 individuals of each species were examined. Vouchers have been retained in the senior authorÕs collection. Whole larvae were examined in ßuid with a dissection stereomicroscope. Spine patterns were some-

Fig. 5. Wet mount of C. megacephala anterior cephalopharyngeal skeleton. The pigmented base of the accessory sclerite is visible as a spot below the mouth hook.

times difÞcult to see if the larva was not fully extended by placing the specimen (alive or dead) in boiling water. Selected specimens of each species were dissected and mounted in Berlese ßuid for examination and photography with a compound microscope. When necessary, specimens were cleared in a solution of 10% KOH at room temperature. Specimens were prepared for scanning electron microscopy by Þxation in osmium tetroxide followed by critical-point drying and gold/palladium sputter-coating. For information on larval anatomy consult Erzinclioglu (1985) and Liu and Greenberg (1989). The characters used to separate larvae or adults of C. albiceps and C. rufifacies are variable, and a small proportion of individuals may be difÞcult to distinguish based on morphology (Tantawi and Greenberg 1993). An alternative method for identifying problematic specimens is based on mitochondrial DNA sequence data (Wells and Sperling 1999).

Fig. 6. Posterior view of anal protuberance showing spinal pattern for (A) C. macellaria and (B) P. regina.

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tance between medial and lateral papillae (Fig. 7B); most spines single-pointed . . . . . . . . . . . . . . . . . . . . . . Protophormia terraenovae Acknowledgments We are grateful for specimens provided by Bernard Greenberg (University of Illinois at Chicago, M. Lee Goff (University of Hawaii), Julio Mendez (Universidad de Panama), Chas Franklin (San Jose State University), and J. P. Spradbery (Australian Commonwealth ScientiÞc and Industrial Research Organization). Scanning electron micrographs were made in The M.D. Socolofsky Microscopy Facility (Louisiana State University) with the assistance of Cindy Henk. The illustrations are by Kevin Wiseman (University of California at Berkeley).

Fig. 7. Dorsal posterior papillae (P) on Þnal segment of (A) P. regina and (B) P. terraenovae.

Key to 3rd Instars of Chrysomyinae from Carrion in the Continental United States 1. Larva with rows of conspicuous tubercles (Fig. 2) . . . . . . . . . . . . . . . . . . . . . . . . 2 Larva without tubercles . . . . . . . . . . . . . 3 2. Dorsal tubercles with relatively small apical spines, usually pointed toward center (Fig. 3A), scales on base of tubercles without pigmented points . . . . . . . . Chrysomya albiceps Dorsal tubercles with relatively large apical spines, usually pointed away from center (Fig. 3B), scales on base of tubercles with pigmented points . . . . . . . Chrysomya rufifacies 3. Covering of Þne setae present, most conspicuous on posterior dorsum (Fig. 4). . . . . . . . . . . . . . . . . . . . . . . . . . . Chrysomya chloropyga Covering of Þne setae absent . . . . . . . . . 4 4. Oral sclerite pigmented . . . . . . . . . . . . . . 5 Oral sclerite unpigmented . . . . . . . . . . . . 6 5. Oral sclerite partially pigmented, visible as dark spot beneath mouth hooks (Fig. 5). . . . . . . . . . . . . . . . . . . . . . Chrysomya megacephala Oral sclerite completely pigmented, visible as a spike between mouth hooks . . . . . . . . . . . . . . . . . . . . . . . . . . . Compsomyiops callipes 6. Pigmented spines above anus forming a V-shaped pattern (Fig. 6A); dorsal spines absent on posterior margin of segment 11 . . . . . . . . . . . . . . . . . . . . . . . . . . Cochliomyia macellaria Pigmented spines above anus forming an oval cluster (Fig. 6B); dorsal spines present on posterior margin of segment 11 . . . . . . . 7 7. Medial posterior papillae (P1 in Fig. 7A) relatively small; distance between medial posterior papillae ⱖ distance between medial and lateral papillae (P3); most spines doublepointed . . . . . . . . . . . . . . . Phormia regina Medial posterior papillae relatively large; distance between medial posterior papillae ⬍ dis-

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