Genus Stelis Panzer, 5 taxa
This is a genus of parasitic Megachilidae that parasitize other Megachilinae.
Three subgenera, Dolichostelis Parker and Hurd, Heterostelis Timberlake (formerly in Protostelis Friese), and Stelis Panzer, are found in Florida. Michener (2001) considers all of these to be subgenera of the larger genus Stelis.
Keys to the subgenera (from Michener 2007)
For both males and females
1. Hind tibia with a single prominent tooth or tibial spine (usually hidden among hairs) on margin near apex of posterior margin of tibia; hind basitarsus with strong lamella-like carina along posterior margin, separated by longitudinal depression from longitudinal thickening of outer surface of basitarsus..S. (Heterostelis)
Hind tibia with an apical median tooth or tibial spine and a less prominent, rounded projection near apex of posterior margin of tibia; hind basitarsus unmodified..2
2. Base of propodeum with zone set off by carina and divided into a series of pits, this zone projecting subhorizontally behind vertical metanotum; anterior surface of mesepisternum impunctate at least below and set off from lateral surface by sharp angle or weak omualar carina..S. (Dolichostelis.)
Base of propodeum vertical or sloping, rarely subhorizontal,
without series of pits or such pits usually present only laterally,
this zone with about same slope as metanotum, anterior surface of mesepisternum puncate, omaular carina absent..S. (Stelis s. str)
Notes: Subgenera Heterostelis and Dolichostelis share a sparsely punctate and carinate omaulus, the carina strong in Heterostelis but weak in Dolichostelis. This character is used in this key to separate Dolichostelis from the subgenus Stelis. However, it is the deep elongate depression and strong lamella-like carina on the hind basitarsus that is used to separate Heterostelis from Dolichostelis as well as from Stelis. Dolichostelis does have a weak and variable lamella-like margin on the hind basitarsus but lacks the depression.
Dolichostelis Parker and Hurd, 1 species
(Mitchell placed these in Stelis).
These are cleptoparasites in nests of Megachile
(Chelostomoides)
Megachilidae: Stelis louisae Cockerell (= S. floridana Graenicher, = S. costalis Mitchell (misidentification), and S. costalis Krombein (misidentification)
County Records: Alachua, Hardee, Highlands, Levy, Manatee, Marion, Miami-Dade, Putnam, Santa Rosa
Locations: Bowling Green, Brandon, Ordway-Swisher Biological Station, San Felasco Hammock Preserve State Park, University of Florida Campus.
Dates: May, October
Plants: Balduina angustifolia, Gaillardia pulchella, Helianthus annuus, Pityopsis graminifolia
Notes: This species has a tortured history of misidentifications. For details, see Parker, F. D. and G. E. Bohart. 1979. Dolichostelis, a new genus of Parasitic Bees (Hymenoptera: Megachilidae). Journal of the
Kansas Entomological Society 52(1): 138-153. The taxa called S. floridana is a form that has more extensive and darker red-orange markings than populations further to the north but there are intermediates. Their map
shows it occuring throughout the peninsula but absent from the panhandle.
Female
Male
Subgenus Heterostelis Timberlake, 3 species
These are likely parasites of the genus Trachusa
Key to females of Stelis, subgenus Heterostelis
1. Larger (13mm); mandibles more elongate, 2nd tooth being midway between apex and inner angle; tergum 6 obtusely angulate on each side..S. grossa
Smaller (10mm); mandibles shorter, 2nd tooth much nearer apex than to inner angle; tergum 6 regularly rounded..2
2. Abdominal terga 1 and 2 broadly ferruginous medially, between the yellow lateral maculations..S. australis floridensis
Terga 1 and 2 black medially..S. australis australis
Males have not been described for S. grossa but were found in Ordway-Swisher Biological Station.
County Records: Alachua, Levy, Putnam, Volusia
Locations: Cassadega
Dates: May (1), August (1)
Plants:
Notes: Thorp (1966) listed it for Florida from Volusia county.
County Records: Alachua, Citrus, Clay, Levy
Locations: Inverness
Dates: May-August
Plants:
Notes: This subspecies appears to be restricted to Florida. These two subspecies may represent nothing more a color cline according to Thorp (1966) but they have been found together. Possibly, coloration is dependent on local environmental conditions that affect the nesting larvae.
Male
County Records: Alachua, Putnam
Locations: Ordway-Swisher Biological Station.
Dates: October
Plants: Balduina angustifolia
Notes: Was described from Florida, Thorp (1966). Females and males found more recently in the University of Florida Ordway-Swisher Biological Station in Putnam County (Hall and Ascher 2014). Hurd (1979) lists it also from Ft. Morgan, Alabama (Baldwin County).
Female
Male
Subgenus Stelis Panzer, 2 species
Key to females and males of Florida Stelis, subgenus Stelis
Entirely black, lacking maculations even on abdomen ..S. ater
Abdomen to some degree maculated ..S.labiata
Megachilidae: Stelis ater Mitchell
County Records: Alachua, Collier, Levy, Sarasota
Locations: Corkscrew Swamp, Kanapaha Prairie, Paynes Prairie Preserve State Park
Dates: January, March, April
Plants:
Notes: Endemic to Florida. Previously known only from the southwestern coastal region. First males found at Paynes Prairie, Alachua County (Hall and Ascher 2010). This species is a cleptoparasite of
Osmia chalybea
Female
Male
County Records: Levy, Putnam
Locations:
Dates: April
Plants:
Female
Male
(photos of males are of specimens from Louisiana)
