Tribe Anthidini

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)

Ste gro hindbasitar

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

Ste lou hindtib
Ste ater hindtib

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.)

Ste lou petio
Ste lou omaulus

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)


Ste ater omaulus

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

stelou map.jpg (72761 bytes)

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

Dorsal Habitus
Vertex Scutum Scutellum
Petiole
Lateral Habitus
Gena Pleura
Ventral Habitus
sterna
Mid-tibial Spines
Hind Tibia

Male

Dorsal Habitus
Vertex Scutum Scutellum
Petiole
Note maculation differs from previous slide
Lateral Habitus
Gena Pleura
Ventral Habitus
Sterna
Mid-tibial Spines
Hind Basitarsus
Hind Tibia


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.


Megachilidae: Stelis australis australis Cresson

County Records: Alachua, Levy, Putnam, Volusia

steausaus.jpg (74033 bytes)

Locations: Cassadega

Dates: May (1), August (1)

Plants:

Notes: Thorp (1966) listed it for Florida from Volusia county.

Megachilidae: Stelis australis floridensis Mitchell

County Records: Alachua, Citrus, Clay, Levy

steausflo.jpg (74350 bytes)

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


Megachilidae: Stelis grossa Mitchell

County Records: Alachua, Putnam

stegro map.jpg (71992 bytes)

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

Mandibles Clypeus
Vertex Scutum Scutellum
Lateral Habitus
Gena Pleura
Propodeum - Lateral Side
Ventral Habitus
Sterna
Mid-tibial Spines
Hind Basitarsus
Genital Armature - Dorsal Side

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

steate map.jpg (71888 bytes)

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

Dorsal Habitus
Mandibles Clypeus
Vertex Scutum Scutellum
Lateral Habitus
Gena Pleura
Ventral Habitus
Sterna
Mid-tibial Spines
Genital Armature - Dorsal Side

Megachilidae: Stelis labiata (Provancher)

County Records: Levy, Putnam

stelab map.jpg

Locations:

Dates: April

Plants:

Female

Male

(photos of males are of specimens from Louisiana)

Dorsal Habitus
Vertex Scutum Scutellum
Lateral Habitus
Gena Pleura
Ventral Habitus
sterna
Mid-tibial Spines
Genital Armature - Dorsal Side