Try
http://www.birdblowfly.com/images/Publications/Keys.pdf by Terry Whitworth for a specimen key, and morphological figures.
Males can be recognized by the reduced distance between the eyes dorsally, compared to females.
e.g.
L. sericata is the only Northeastern species with 3 post-sutural acrostichals and an orange basicosta, and frequently has a tomentose anterior scutum:
L. cuprina has a uniquely coppery-brown metallic body (first image), although some
L. sericata come close if at least somewhat more reddish (second image).
L. cuprina typically has especially distinct tomentose patches on the frons that, in combination with its coloration, make it possible to identify
L. cuprina from very poor images.
Neomyia cornicina are similar but unlike
Lucilia have only 1 pair of acrostichal bristles, not 2-3, and have a more extensively metallic head, including the occiput and genae:
Key to species
1.
Frons up to 21% of head width (males)
(1) ... 2
Frons at least 24% of head width (females)
(1); if uncertain, males key here too... 10
2.
frons separating eyes, at narrowest, at least 7% of head width ... 3
frons separating eyes, at narrowest, about 1% of head width ... 7
3.
frons at narrowest more than 20% head width, 3 acrostichals, orange basicosta; often uniquely dull coppery-brown (Southern) ...
L. cuprina
frons at narrowest no more than 15% head width .... 4
frons at narrowest approaching 20% of head width, 3 acrostichals, black basicosta (Far North, Alaska to Labrador) ...
L. magnicornis
4.
basicosta, palps yellow-orange ... 5
basicosta, palps dark ... 6
5.
2 post-sutural acrostichals, frons at narrowest ~10% of head width (SE USA) ...
L. cluvia
3 post-sutural acrostichals, frons at narrowest ~13% of head width (widespread) ...
L. sericata
6.
3 post-sutural acrostichals, male frons ~6-10% of head width (widespread) ...
L. silvarum
2-3 post-sutural acrostichals, male frons ~10% of head width (Western) ...
L. bufonivora
2-3 post-sutural acrostichals, male frons 12-16% of head width (Western) ...
L. elongata
7.
basicosta yellow-orange, 2 to 3 acrostichals ... 8
basicosta tan to dark, 2 acrostichals ... 9
8.
3 post-sutural acrostichals (Western) ...
L. thatuna
2 post-sutural acrostichals (widespread) ...
L. coeruleiviridis
9.
T4 with long erect setae (Northern, Southwestern) ...
L. illustris
T4 without long erect setae (Southwestern) ...
L. mexicana
(rare in TX, FL) ...
L. eximia
10.
Basicosta, palps dark ...
2-3 acrostichals in L. magnicornis, L. elongata, L. bufonivora (Western/widespread in Canada) or 3 acrostichals in
L. silvarum (widespread)
Basicosta tan/dusky to dark, palps yellow/orange (ambiguous cases key both ways) ... 13
Basicosta, palps yellow/orange ... 11
11.
3 post-sutural acrostichal setae ... 14
2 post-sutural acrostichal setae ... 12
12.
Basicosta tan/dusky to dark ... 13
Basicosta yellow/orange ... 15
13.
(Northern, Southwestern) ...
L. illustris
(Southwestern) ...
L. mexicana
(rare in TX, FL) ...
L. eximia
14.
frons at narrowest less than 1/2 head width; never dull coppery-brown (West of Rockies) ...
L. thatuna
frons at narrowest ~1/2 head width; often uniquely dull coppery-brown (Southern) ...
L. cuprina
frons at narrowest ~1/2 head width; never dull coppery-brown (widespread) ...
L. sericata
15.
gena with dark setae ...
L. coeruleiviridis (widespread)
gena with pale setae ...
L. cluvia (Southeastern)
Sources, other than BugGuide and personal observations:
Tantawi, Whitworth, 2014. First record of Lucilia bufonivora Moniez, 1876 (Diptera: Calliphoridae) from North America and key to North American species of the
L. bufonivora species group. Zootaxa. 3881(2): 101-124
(1) Whitworth, 2006. Keys to the Genera and Species of Blow Flies (Diptera: Calliphoridae) of North America north of Mexico. Proceedings of the Entomological Society of Washington. 108(3): 689-725.
Jones, Whitworth, Marshall, 2019. Blow flies of North America: Keys to the subfamilies and genera of Calliphoridae, and to the species of the subfamilies Calliphorinae, Luciliinae and Chrysomyinae. https://cjai.biologicalsurvey.ca/jwm_39/jwm_39_128.HTM
