Tag Archives: Monomorium floricola

Flower Ant | Monomorium floricola (Jerdon)

California Pest Rating for
Monomorium floricola (Jerdon): Flower Ant
Hymenoptera: Formicidae
Pest Rating: A

 Initiating Event:

On February 21, 2017 Dr. Kevin Williams identified ants collected during inspections of beehives recently shipped into California from Florida as Q-rated Monomorium floricola.  A pest rating proposal is required to assign a permanent pest rating.

History & Status:

Background:  Monomorium floricola is a widely distributed tropical arboreal ant1.  It is a generalist that feeds on honeydew, dead insects, and any other available protein and sugar sources.  It nests in trees, bushes, and structures such as beehives and can be transported long distances when those items are moved.

Worldwide Distribution: Monomorium floricola is widespread in almost all of the tropical areas of the world1 and is widespread and abundant in both Florida and Hawaii.  It was first collected in Florida in 1887 and has not spread north of Putnam County, likely due to its tropical nature2.  Records of the ant from other continental states show that the ants are not able to establish there.  Records from Mississippi were collected on palm trees transported from Florida and planted in a warm coastal location4.  There are no records of the ants spreading from this location.  There is an old catalog record of the ants in Alabama but more recent comprehensive surveys of the ant fauna have not been able to find any of the ants6.  The only known collection of Monomorium floricola in Arizona occurred inside the Biosphere 2 greenhouse structure where plants had been imported from a large number of sources1,7.

Official Control: Monomorium floricola is not known to be under official control in any states or nations.  It is not listed on any nation’s harmful organism list3.

California Distribution:  Monomorium floricola has not been found in the environment of California.

California Interceptions:  Between January 1, 2010 and February 23, 2017 Monomorium floricola was intercepted by CDFA 16 times.  In addition to the recent beehive interception mentioned above, recent interceptions have occurred on plants from Hawaii, firewood from Florida, guavas from Mexico, and other beehives from Florida.

The risk Monomorium floricola (flower ant) would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: North of 35˚ latitude, Monomorium floricola has not been found to be established outdoors1.  There it has only been found in greenhouses and other heated buildings1.  35˚ latitude roughly corresponds with the Tehachapi Mountains in California.  Most of the records north of 30˚ latitude are also in heated buildings1 and/or associated with plants that have been moved from more southern locations.  The entire state of California is located north of 32˚.  It is therefore likely that this ant will only be able to establish in the warmest parts of California including greenhouses and heated buildings.  Monomorium floricola receives a Low (1) in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California.  Score:

Low (1) Not likely to establish in California; or likely to establish in very limited areas.

Medium (2) may be able to establish in a larger but limited part of California.

High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Monomorium floricola is a generalist forager that feeds on a wide variety of protein and sugar sources.  It receives a High (3) in this category.

Evaluate the host range of the pest. Score:

Low (1) has a very limited host range.

Medium (2) has a moderate host range.

High (3) has a wide host range.

3) Pest Dispersal Potential: Monomorium floricola does not fly, giving it less local dispersal potential than many other ants.  However, it can be easily transported long distances when infested plants, firewood, or beehives are moved.  It has colonized most of the tropical areas of the world, demonstrating high long distance dispersal potential.  Monomorium floricola is abundant where it is found, indicating high reproductive potential.  The ant receives a High (3) in this category.

Evaluate the natural and artificial dispersal potential of the pest. Score:

Low (1) does not have high reproductive or dispersal potential.

Medium (2) has either high reproductive or dispersal potential.

High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Monomorium floricola is not documented to be a pest outside of urban areas anywhere in the world.  The ant is not expected to lower any crop yields or values.  It is not expected to disrupt markets.  There are no reports of this ant changing cultural practices in agriculture anywhere in the world.  The ant is not known to vector other organisms or interfere with water supplies.  It is possible that it could harm biological control agents as it tends to honeydew producing insects.  However, there are already other ants in California that interfere with biological control such as argentine ant (Linepithema humile) so impacts will likely be minimal.  Monomorium floricola receives a Low (1) in this category.

Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Low (1) causes 0 or 1 of these impacts.

Medium (2) causes 2 of these impacts.

High (3) causes 3 or more of these impacts.

5) Environmental Impact: Invasive ants such as Monomorium floricola may cause slow, long-term ecological changes that have the potential to lower biodiversity, disrupt natural communities, or change ecosystem processes.  Flower ant is not likely to directly affect threatened or endangered species or disrupt critical habitats.  In areas where it is abundant such as Florida, the ants are inconspicuous, difficult to find, and seldom observed.1 However, as a nuisance pest indoors they are a regular source of calls to pest control companies and do result in new treatment programs5.  The ants are slow-moving, unaggressive, and unlikely to sting and are therefore unlikely to have significant cultural impacts.  Monomorium floricola receives a High (3) in this category.

Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

Low (1) causes none of the above to occur.

Medium (2) causes one of the above to occur.

High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Monomorium floricola (Flower Ant):  Medium (11)

Add up the total score and include it here.

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

6) Post Entry Distribution and Survey Information: Monomorium floricola is not known to be established in the environment of California and receives a Not Established (0) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Not established (0) Pest never detected in California, or known only from incursions.

Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: Medium (11)


There are already other invasive tramp ant species established in California.  These other ants may preclude some of the economic and environmental impacts of Monomorium floricola.  However, there is a lot of uncertainty with the introduction of tramp ants to California.  It is possible the ants could interact with well-irrigated crops in San Diego, Imperial, and Riverside counties causing unanticipated economic and environmental impacts unlike anything that has been previously experienced in other locations.

Conclusion and Rating Justification:

Monomorium floricola has never been found in the environment of California.  If it were to establish in the state, the ant is likely to have significant environmental impacts in greenhouses, heated buildings, and possibly outdoors in the warmest areas of southern California.  An “A”-rating is justified.


1 Wetterer, James K. 2010. Worldwide spread of the flower ant, Monomorium floricola (Hymeoptera: Formicidae).  Myrmecological News 13: 19-27.  https://www.researchgate.net/profile/James_Wetterer/publication/256979598_Worldwide_spread_of_the_flower_ant_Monomorium_floricola_Hymenoptera_Formicidae/links/0c9605258d5c35ac5e000000.pdf

2 AntWiki: Monomorium floricolahttp://www.antwiki.org/wiki/Monomorium_floricola

3 USDA Phytosanitary Certificate Issuance & Tracking System (PCIT) Phytosanitary Export Database (PExD).  https://pcit.aphis.usda.gov/pcit/

4 MacGown, J.A. and J.G. Hill. 2010. Two New Exotic Pest Ants, Pseudomyrmex gracilis and Monomorium floricola (Hymenoptera: Formicidae) Collected in Mississippi. Midsouth Entomologist.  http://midsouthentomologist.org.msstate.edu/Volume3/Vol3_2_html_files/Vol3_2_007.html

5 Klotz, John H., John R. Mangold, Karen M. Vail, Lloyd R. Davis Jr., and Richard S. Patterson. 1995. A survey of the urban pest ants (Hymenoptera: Formicidae) of Peninsular Florida. Florida Entomologist 78(1).  https://ag.tennessee.edu/EPP/Publications1/A%20Survey%20of%20the%20Urban%20Pest%20Ants%20of%20Peninsular%20Florida.pdf

6 Forster, Jason Allen. 2003. The ants (Hymenoptera: Formicidae) of Alabama. A thesis submitted to the graduate faculty of Auburn University.  https://etd.auburn.edu/bitstream/handle/10415/772/FORSTER_JASON_28.pdf?sequence=1

7 Wetterer, J.K., S.E. Miller, D.E. Wheeler, C.A. Olson, D.A. Polhemus, M. Pitts, I.W. Ashton, A.G. Himler, M.M. Yospin, K.R. Helms, E.L. Harken, J. Gallaher, C.E. Dunning, M. Nelson, J. Litsinger, A. Southern, and T.L. Burgess. 1999. Ecological dominance by Paratrechina longicornis (Hymenoptera: Formicidae), an invasive tramp ant, in Biosphere 2. Florida Entomologist 82(3): 381-388.  http://journals.fcla.edu/flaent/article/view/59473/57152

Responsible Party:

Jason Leathers, 1220 N Street, Sacramento, CA, 95814, (916) 654-1211, plant.health[@]cdfa.ca.gov.

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Pest Rating: A

Posted by ls