Owl Moth 

Thysania zenobia (Cramer, 1777)

Owlet Moth Family Noctuidae


Photos / Range / Early / Islands / Records / Caterpillars / Hostplants / Etymology / Biography / Bibliography

Dates: Apr / May / Jun / Jul / Aug / Sep / Oct / Nov / Dec

Interactive Map of North American Records

Return to Texas Entomology - Compiled by Mike Quinn


 

Owl Moth (Thysania zenobia)

(at bait)

Avenue I & 15th Street
Galveston, Galveston Co., Texas
21 October 1971 (W.W. McGuire)


Pix from TX & SD - Dorso -Verso Pix - Specimen from Canada

Two in Riker Mount (above Black Witch moths)

See also: Black Witch (Ascalapha odorata) & White Witch (Thysania agrippina)


Texas County Records for Thysania zenobia

Owl Moth - Thysania zenobia
Many additional records now known

Interactive Map of North American Owl Moth Records


Dates and Locations

     The Owl Moth has been recorded throughout eastern North America, Central America, and ranges south at least to the southeastern-most Brazilian state of Rio Grande do Sul. It is also found on the larger Caribbean Islands of Cuba, Hispaniola, Jamaica and Puerto Rico. It is also found on Bermuda and the Galapagos Islands. However, unlike the much more common Black Witch (Ascalapha odorata), there are no U.S. Owl Moth records west of Texas, nor is it found on Hawaii. 

     Covell (1986) reports this moth flying in "all months in southern Florida and southern Texas," however Kimball (1965), in his annotated checklist of Florida Lepidoptera, lists only three specific records for Florida, one in Aug 1904 and two in July. The latter two specimens are in the American Museum of Natural History and were collected in 1916 (Suzanne Rab Green, pers. comm., April 2008). Heppner's (2003) revised catalog of Florida Lepidoptera adds no new T. zenobia records and reports the species as a "stray". I am unaware of any T. zenobia Florida records for the previous 90 years.

     I have found no Texas records from January through May. With but one exception, all U.S. and Canada records follow the June onset of the rainy season in Mexico.

     In 34 years of continuous light trapping in Louisiana, Vernon Brou (2003) collected only three specimens of Owl Moths in July, September, and November. 

     Covell (1986) reported that the Owl Moth migrates north in September and October. However, data from approximately 60 Owl Moth records indicate that it migrates north as early as late June.

     Caveney (2007) reports 14 Owl moth records from Canada. The western-most and northern-most record was collected in Regina, Saskatchewan, Canada. Neil (1979) reports the eastern-most record at Dartmouth, Nova Scotia, Canada. It was collected in late summer or early fall 1944. The specimen is in the Nova Scotia Museum of Natural History, Halifax.

     The southern-most records are perhaps the two specimens (collected in 1946 & 1951) reported by Specht et al. (2004) from Pelotas, Rio Grande do Sul, the southernmost state in Brazil. However, Pastrana (2004) reports the moth from Argentina and Uruguay with no further data. Uruguay and southern Brazil are approximately 30 degrees south of the equator. Note that the northern-most records are at approximately 50 degrees north of the equator.

Early North American Records

     Early North American records include Grote (1875) who reported in a foot note that "Professor [Charles Valentine] Riley informs me that this species occurred at Davenport [Iowa]." Kilman (1889) gave a detailed report of a specimen he collected while sugaring for Catocala outside of Ridgeway, Ontario, Canada on August 22, 1888. The specimen is curated in the Ontario Agricultural College. Kilman wrote of his encounter with the moth:

"The sensation which a hunter is said to experience on sighting his first deer came upon me, for I was unprepared for such an encounter. However, the monster was taken."

     Dyar (1902), unaware of Grote's and Kilman's records, states the moth's range as Florida and South America without elaboration. Felt (1907) led off his annual report on the insects of New York with a short discussion of an Owl Moth found in Albany. Felt doubts that the moth arrived under its own powers:

A remarkable large South American moth (Thysania zenobia Cramer) was taken in Albany the last of September. This magnificent moth has a wing spread of about 5 inches and its occurrence in this city is undoubtedly due to its having been brought north with a boat load of bananas or other tropical fruit. This capture is an example of the way in which insects are distributed through commercial agencies, though in the present instance it happens to be a species which can not sustain itself in this latitude.

     Farquhar (1934), in his survey of New England Lepidoptera reported only two Owl Moths, one from Massachusetts and the other from Rhode Island. 

     Rings et al (1992) show five county records collected between 1890 and 1987 in Ohio from late August to early October. Specific Ohio data provided below from The Ohio Lepidopterists, with support from the Division of Wildlife of the Ohio Department of Natural Resources.

     Ziemer (1948) from Kewaunee, Wisconsin (east of Green Bay) reported three Owl Moth records from his location over the previous nine years:

     In Sept. of 1945 a farmer friend of mine brought in a large moth he found in a whey barrel on his farm. It turned out to be a very torn male T. zenobia. In August 1940 I observed a large specimen on bait. In September 1942 a very fine male T. zenobia was attracted to light on my back stoop. 
     I find it difficult to believe that these moths can be blown by winds this far north and still be in quite perfect condition and also occur so frequently.

An Island Affinity?  

     There are 142 T. zenobia records in the Harvard University's Caribbean Plants & Insects Database from Hispaniola and Jamaica (as of April 2008). All Owl Moth specimens in this database are curated at the Carnegie Museum of Natural History. The largest number of Owl Moths collected anywhere was the 120 collected on the Dominican Republic from 1985 to 2003. Eight specimens were collected on the Haiti side of Hispaniola. The specimens of this set with data were collected from 1925 to 1934. Ten Owl Moths were collected on Jamaica from 1891 to 1936. These Caribbean records are primarily from July to November with only a few recorded from March, May and June. The Caribbean Islands may be the source of the few strays to Florida.

     Gundlach (1881) reports three Owl Moths, all in eastern-most Cuba in vicinity of what is now Guantánamo. However, neither Wolcott (1936) nor Schaus (1940) report the moth for Puerto Rico. The presence/abundance of the moth has apparently changed as Dr. Luis Roberto Hernández (pers. comm., 9 Apr 2008) reports that it is now "very common [and] found in the west and central mountains [of Puerto Rico] and in my experience is common in all Cuba. I suppose because Cassia spp. and Senna spp. are very abundant in both islands." 

     Roque (1999) reported the first records the Owl Moth for the Galapagos Islands which lay some 600 miles off the west coast of South America. Roque collecting four fresh Owl Moths on two Galapagos Islands from April 1996 to March 1997. 

Between 20 and 25 April 1996, three fresh males were collected in a Mercury vapor light trap near Asilo de la Paz, Floreana Island, at 338 m elevation. The trap was located at the border of the agricultural zone and native forest. In March 1997, I collected another specimen in a forest of the endemic composite, Scalesia pedunculata Hook at Los Gemelos, Santa Cruz island, at 580 m elevation, feeding in a bait trap (mixture of rotting fruit). The fresh condition of these specimens suggested that they were from a population extant on the island, rather than migrant.

Records Listed by Month

Month Total Texas CAN
Apr 1

May 1 1

June 3 3
July 8 1 2
Aug. 20 7
5
Sept. 20 6 5
Oct. 18 14 1
Nov. 8
8
Dec. 2 2
None 3 1
2
Totals 113 41
15





Arkansas Washington Co. Fayetteville April 26, 1979 UAAM

Texas Starr Co.
Falcon Heights
May 8, 2012
At bait, Berry Nall

 

================ General Beginning of Rainy Season in Mexico =================

 

 

Texas Dallas Co.
Dallas
June 6, 2012
Photo (sb MAQ)
Texas Midland Co. Midland June 27, 2004 (sight record)
Texas Midland Co. Midland June 29, 2004 (sight record)

Texas Midland Co. Midland July ~1, 2004 (sight record)
Kansas
Meade Co.
Meade
July 13, 2012
Photo (sb: MAQ)
Ontario
Point Pelee July 22, 1941 CNC
Illinois Champaign Co. Trelease Woods July 24, 1977 INHS
South Dakota Brookings Co. 4 mi northeast of White July 28, 2004 Photo
Saskatchewan
Regina (western & northern-most rec.) July 30, 1973 RSM
Louisiana

July ??, 19?? Brou, 2003
Florida
Chokoloskee  July ??, 19?? two, AMNH

Texas Cameron Co. Audubon Sabal Palm Sanctuary Aug 02, 1997 LepSoc-SS
Connecticut Fairfield Co. Greenwich Aug 03, 1941 Remington, 1950
Iowa Hardin Co. Iowa Falls (at bait) Aug 12, 1996 LepSoc-SS

New Brunswick


Renforth (eastern-most record)

Mid-Aug 1903 Petch, 1939
IllinoisLaSalle Co.Synder's Grove, MendotaAug 16, 2007on sugar slop
Arkansas Washington Co. Fayetteville vicinity Aug 17, 1964 UAAM
Quebec 

Sainte-Anne-de-Bellevue, Morgan Arboretum  

Aug 17, 1972 at bait, a male
Texas Lee Co.
Aug 19,1978 TAMUIC
Ontario
Ridgeway   Aug, 20, 1888 Ont. Ag. College
New York Queens Co. Jamaica Bay Wildlife Refuge Aug 20, 2004 (sight record)
Quebec 
Quebec City Aug 21, 1946 Handfield (1999)
Kentucky McCraken Co. 6 mi. SW of Paducah (at light) Aug 23, 1974 Covell, 1999
South Dakota Stanley Co. 2 mi S Oahe Dam Aug 24, 2004 at bait, LepSoc-SS
Florida
Egmont Key Aug 26, 1904 University Miami
New York Monroe Co. Pittsford   Aug 26, 2006 Photo (sb:MAQ)*
Illinois Union Co. Bald Knob (Alto Pass)  Aug 29, 1994 male, coll. Jim Wiker
Texas Lubbock Co. Lubbock Aug 30, 2006 male, photo (sb:MAQ)
Wisconsin Kewaunee Co. Kewaunee Aug ??, 1940 Ziemer (1948)
North Dakota Cass Co.  Fargo Aug ??, 1957 Male, NDSU
Saskatchewan
Riceton Aug/Sep 1930 CNC

Manitoba
Cartright

Sept 05, 1906

Petch, 1939

Illinois Marshall Co. Lacon Sept 05, 1930 INHS
Michigan Oakland Co.
Sept 06, ???? Moore (1955)
Ontario Middlesex Co. London Sept 08, 2004 Univ. of Western Ont.
North Dakota Cass Co. Fargo Sept 8-12, 1997 Female
Massachusetts Norfolk Co. Holbrook Sept 09, 1923 Farquhar 1934
Massachusetts Dukes Co. Martha's Vineyard (nr. Chilmark) Sept 10, 1941 Jones & Kimball, 1943
Arkansas Washington Co.
Sept 12, 1964 UAAM
Ontario
Hamilton Sept 15, 1985 CNC
Minnesota
Stearns Co.
St Cloud State University, St. Cloud
Sept 1973
Saint John's University
Illinois Peoria Co. West Lamarsh Creek Sept 16, 2001    LepSoc-SS

Ontario


Toronto

Sept 19, 1906 Petch, 1939
TexasHaysSan MarcosSept 19, 2011BugGuide
Wisconsin Bayfield Co. N. Great Lakes Visitor Center, nr. Ashland Sept 21, 1999 LepSoc-SS, link to pic
Ontario
Chatham Sept 24, 1944 CNC
TexasHarrisClear Lake CitySept 24, 2011 Fide David Kent
Texas Bexar Co. San Antonio Sept 26, 2003 Photo
Illinois Rock Island Co. Rock Island Sept 28, 1945 INHS
Ohio Seneca Co.
Sept 30, 1890 Ohio Lepidopterists
Wisconsin Kewaunee Co. Kewaunee Sept ??, 1942 Ziemer (1948)
Wisconsin Kewaunee Co. Kewaunee Sept ??, 1945 Ziemer (1948)
Louisiana

Sept ??, 19?? Brou, 2003

Ohio Cuyahoga Co.
Oct 01, 1953 Ohio Lepidopterists
Michigan Midland Co.
Oct 02, ???? Moore (1955)
Arkansas Washington Co. Fayetteville vicinity Oct 02, 1964 UAAM
Quebec 
Quebec City Oct 04, 1938 Handfield (1999)
Texas Nueces Co. Corpus Christi Oct 04, 2001 LepSoc-SS
Texas Kenedy Co. King Ranch Oct 06, 1995 LepSoc-SS
South Carolina Pickens Co. Clemson Oct 08, 1961 Clemson (CUAC)  
TexasStarr Co.Halcon HeightsOct. 08, 2011Photos sb:MAQ
Tennessee Sevier Co. Gatlinburg, nr. Great Smoky Mountains NP Oct 09, 1951  GSMNP Coll.
Ohio Crawford Co.
Oct 13, 1951 Ohio Lepidopterists
Texas
San Patricia Co.
2 mi. NE Aransas Pass
Oct 18, 2011
Photo (sb MAQ)
Texas Gregg Co. Longview Oct 19, 1976 LepSoc-SS
Texas Galveston Co. Galveston Oct 21, 1971 W.W. McGuire
Texas Willacy Co. So. Padre Island Oct 25, 2001 (sight)
Texas
Travis Co.
Montopolis Rd., Austin
Oct 27, 2011
Photo (sb MAQ)
Texas Nueces Co. Corpus Christi Oct 29, 2001 LepSoc-SS
Texas Cameron Co. Brownsville Oct 30, 2004 Specimen, pic(sb:MAQ)
Aransas Washington Co. Fayetteville vicinity Oct 31, 1970 UAAM

Texas Calhoun Co. Port O'Connor Nov 11, 2005 fresh male, at bait, Photo
Texas Starr Co. Falcon Heights Nov 08, 2011
Berry Nall
Texas Starr Co. Roma Nov 18, 1995 LepSoc-SS
Louisiana

Nov ??, ???? Brou, 2003

Texas Erath Co. Stephenville Dec ??, 19?? TAMU

Iowa Scott Co. Davenport    (Earliest Record) None stated Grote (1875)
Nova Scocia
Dartmouth    (Eastern-most Record) 1944 Neil (1979)
Ontario
London None stated CNC

     * (sb: MAQ) = Photograph seen by Mike A. Quinn


Caterpillars

     Janzen & Hallwachs (1999) show six T. zenobia caterpillar images in their database. Below are some close up images:

Dorsal view of the head and thorax - Lateral view of abdomen - Ventral view of abdomen

Foodplants

     The following host plants are from Janzen & Hallwachs (1999), Robinson et al. (2002), and Specht et al. (2004):

Fabaceae - Legume or Pea Family

Senna bicapsularis (L.) Roxb. Janzen & Hallwachs (1999)

Cassia ferruginea (Schrader) Schrader ex DC. Robinson et al. (2002)

Cassia fistulosa L. ex Long & Lakela Robinson et al. (2002), Specht et al. (2004)

Cassia imperialis Hort. Specht et al. (2004)



     Per the USDA Plants Database, only Cassia fistulosa L. occurs in the U.S. where it was introduced into Florida.

Etymology:

Owl Moth - Thysania zenobia (Cramer, 1777)

     T. zenobia is not referred to as the "Owl Moth" due to a resemblance to a nocturnal bird of prey, rather it gained this name due to being one of the largest members of the Owlet Moth Family, Noctuidae. "Owlet" being a diminutive form of "Owl" which is an inappropriate moniker for such a grand moth.

     Thysanus - Greek for a fringe
     Zeno is the common aglicized form of the Greek name Zenon (Ζηνων), derived from the theonym Zeus.

Biography

     Pieter Cramer (May 21, 1721 - September 26, 1776 or 1779) was a wealthy Dutch wool merchant and entomologist.


Request for Help

Please report additional records to entomike@gmail.com
Please include date, location (distance to nearest town) & county of record.

If possible, send a photo, medium resolution preferred. Thanks, Mike


Bibliography  

Biezanko, C.M. & A. Ruffinelli. 1971. Fauna de Lepidoptera del Uruguay. X. Agaristidae, Noctuidae et Thyatiridae. Ministerio de Ganadería y Agricultura, Centro de Investigación en Sanidad Vegetal, Montevideo, Ser. Zool. agríc. Publ. técn. 2: 1-31.

Biezanko, C.M., A. Ruffinelli & C.S. Carbonell. 1957. Lepidoptera del Uruguay. Lista anotada de espécies. Revista de la Facultad de Agronomia, Montevideo. 46:3-149.

Borror, D.J. 1960. Dictionary of Word Roots and Combining Forms. National Press Books, Palo Alto. v + 134 pp.

Brou, V.A., Jr. 2003. Ascalapha odorata (L.) and Thysania zenobia (Cram.) in Louisiana. Southern Lepidopterists' News 25(3):91. Full PDF

Caveney, S. 2007. Owl Moth vagrant in Ontario. The Cardinal.

Covell, C.V.  1984. Field Guide to Moths of Eastern North America. Houghton Mifflin Co., Boston.

Covell, C.V.O. 1999. The Butterflies and Moths (Lepidoptera) of Kentucky: An Annotated Checklist. Scientific and Technical Series Number 6. Kentucky State Nature Preserves Commission, Frankfort.

Cramer, P. [1777]. Uitlandsche Kapellen (Papillons exotiques). Uitl. Kapellen 2(9-16): 1-152.

Distler, D.A. 1989. Rare Occurrence of the Owl Moth, Thysania zenobia (Cramer) Noctuidae, in Kansas. Transactions of the Kansas Academy of Science 92(3-4): 209.

Druce, H. 1891-1900. Lepidoptera-Heterocera. Volume I, Pg 374. In: F.D. Godman & O. Salvin (eds.), Biologia Centrali-Americana. Taylor & Francis, London. 3 vols. 

Dyar, H.G. 1902. A list of North American Lepidoptera and key to the literature of this order of insects. Bulletin of the United States National Museum, No. 52, xix + 705 pp.

Farquhar, D.W. 1934. The Lepidoptera of New England. Ph.D. thesis, Harvard University. 328 pp.

Felt, E.P. 1907. 22d Report of the State Entomologist on injurious and other insects of the state of New York 1906. New York State Museum Bulletin 110: 39-44.

Grossbeck, J.A. 1917. Insects of Florida. IV, Lepidoptera. Bulletin of the American Museum of Natural History 37: 1-148.

Grote, A.R. 1875. Check list of the Noctuidae of America, north of Mexico. I. Bombyciae and Noctuelitae (Nonfasciatae). Reinecke and Zesch, Buffalo, New York. 50 pp.

Gundlach, J. 1881. Contribución á la Entomología Cubana. Havana. xxi + 445 pp.

Handfield, L. 1999. Le guide des papillons du Québec. Version scientifique. Brouquet inc., Québec. 982 p. + 123 plates.

Hayward, K.J. 1969. Datos para el estúdio de la ontogenia de lepidopteros argentinos. Miscelánea del Instituto Miguel Lillo, 31(1): 1-142.

Heppner, J.B. 2003. Lepidoptera of Florida. Part 1. Introduction and Catalog. Arthropods of Florida and Neighboring Land Areas, Vol. 17. Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, FL. x + 670 pp.

Hodges, R.W., T. Dominick, D.R. Davis, D.C. Ferguson, J.G. Franclemont, E.G. Munroe, J.A. Powell editors. 1983. Check list of the Lepidoptera of America North of Mexico (Including Greenland). E.W. Classey Limited and the Wedge Entomological Research Foundation, London. xxiv + 284 pp.

Hoffmann, C.C. 1918. Las mariposas entre los antiguos Mexicanos. Cosmos 1.  

Hogue, C. 1993. Latin American Insects and Entomology. University of California Press, Berkeley. 594 pp.

Holland, W.J. 1903. The Moth Book. Doubleday, Page & Co., New York. 479 pp., 48 plates.

Hooper, R.R. 1990. Check-list of the moths of Saskatchewan. Part 5: Arches Moths, Similar-wings, Grass Moths and Underwings (Catocalinae). Blue Jay 48: 79-83.

Janzen, D. H. and Hallwachs, W. 1999. Philosophy, navigation and use of a dynamic database ("ACG Caterpillars  SRNP") for an inventory of the macrocaterpillar fauna, and its food plants and parasitoids, of the Area de Conservacion Guanacaste (ACG), northwestern Costa Rica (http://janzen.sas.upenn.edu).

Jones, F.M., and C.P. Kimball. 1943. The Lepidoptera of Nantucket and Martha's Vineyard. Publ. Nantucket Maria Mitchell Assoc. 4: 1-217.

Kilman, A.H. 1889. Correspondence: A rare moth. The Canadian Entomologist, 21(1): 240.

Kimball C.P. 1965. The Lepidoptera of Florida; an annotated checklist. Arthropods of Florida and Neighboring Land Areas Vol. 1. Florida Department of Agriculture, Division of Plant Industry. 363 pp.

Moore, S. 1955. An Annotated List of the Moths of Michigan Exclusive of Tineoidea (Lepidoptera). Miscellaneous Publications, Museum of Zoology, University of Michigan, Ann Arbor. No. 88. 87 pp.

Neil, K. 1979. Additions to the Macrolepidoptera of Nova Scotia. Proceedings of the Nova Scotia Institute of Science, 29: 197-200.

Pastrana, J.A. 2004. Los Lepidopteros Argentinos: Sus plantas hospedadoras y otros sustratos alimenticios. Braun, K., G. Logarzo, A. Cordo & R. Di Lorio (coordinadores). Sociedad Entomologica Argentina, Buenos Aires. viii + 334 pp.

Petch, C.E. 1939. General Index to the Thirty-Eight Annual Reports of the Entomological Society of Ontario 1900-1937.  Ontario Department of Agriculture, Toronto, Ontario. 267 pp.

Remington, C.L. 1947. Notes from a Travelling Editor. Pp. 42 in: Remington, C.L. & J.E. Remington (editors). The Lepidopterists' News, 1(4):37-48.

Remington, C.L. 1950. Erebus and Thysania in Connecticut. Pp. 13 in: Remington, C.L. & J.E. Remington (editors). The Lepidopterists' News, 4(1-2):1-24

Rings, R.W., E.H. Metzler, F.J. Arnold & D.H. Harris. 1992. The Owlet Moths of Ohio: Order Lepidoptera, Family Noctuidae. Bulleting of the Ohio Biological Survey 9(2):vi + 219 pp., 8 color plates.

Robinson, G.S., Ackery, P.R., Kitching, I.J., Beccaloni, G.W. & Hernández, L.M. 2002. Hostplants of the moth and butterfly caterpillars of America north of Mexico. 824 pp. [Memoirs of the American Entomological Institute, Volume 69.]

Rockbourne, E.W. & J.D. Lafontaine. 1976. Cutworm Moths of Ontario and Quebec. Canada Department of Agriculture. 164 pp., 40 color plates. 

Roque, L. 1999. Two large tropical moths Thysania zenobia, (Noctuidae) and Cocytius antaeus (Sphingidae) colonize the Galapagos Islands. Journal of the Lepidopterists' Society 53(3): 129-130.

Sala, F.P. 1959. Possible migration tendencies of Erebus odora and other similar species. Journal of the Lepidopterists' Society 13: 65-66.  

Schaus, W. 1940. Scientific Survey of Porto Rico and the Virgin Islands Vol. 12, part 2 - Moths of the family Noctuidae. New York Academy of Sciences, New York. pp. 177 - 290.

Schreiter, R. 1936. Erebus odora L., Thysania zenobia Cram. y Thysania agrippina Cram. (Lepidopt.-Noctuidae). Boletín del Museo de Historia Natural de la Universidad Nacional de Tucumán. 2:29-32, pi. I—II.

Smith, J.B. 1893. Catalogue of the lepidopterous superfamily Noctuidae found in boreal America. U.S. National Museum Bulletin 44: 1-424.

Specht, A., E.J.E. Silva & D. Link. 2004. Noctuídeos (Lepidoptera, Noctuidae) do Museu Entomológico Ceslau Biezanko, Faculdade de Agronomia Eliseu Maciel, Universidade Federal de Pelotas, RS. Revista Brasileira de Agrociência, 10(4): 389-409. 

Tietz, H.M. 1972. An index to the described life histories, early stages and hosts of the Macrolepidoptera of the continental United States and Canada. Allyn Museum of Entomology, Sarasota. 

Williams, C.B. 1958. Insect migration. Collins, London. 235 pp.

Wolcott, G.N. 1936. Insectae Borinquenses- a revised annotated checklist of the insects of Puerto Rico. Journal of Agriculture, University of Puerto Rico 20(1): 1-627.

Ziemer, S.E. 1948. Erebus odora & Thysania zenobia in Wisconsin. Pp. 34 in: Remington, C.L. & J.E. Remington (editors). The Lepidopterists' News, 2(3):25-36

Additional Publications on North American Migratory Insects


19 July 2012 © Mike Quinnentomike@gmail.com / Texas Entomology