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16 August 2021 The Seasonal Reproductive Status of Tawny Crazy Ant Queens (Hymenoptera: Formicidae) in Florida
David Oi
Author Affiliations +
Abstract

The tawny crazy ant, Nylanderia fulva (Mayr) (Hymenoptera: Formicidae), is an invasive ant that is spreading in the southern USA. The control of invasive ants requires an understanding of their biology to implement measures of suppression such as strategically applying ant baits to eliminate queens. Nylanderia fulva queens were collected monthly in north central Florida and dissected to determine their seasonal reproductive status. The percentages of queens with > 50 eggs increased from 26% in winter to a peak of 68% in summer, while queens with < 10 eggs was below 20% per season. Thus, eggs were present in queens throughout the yr. Likewise, mated queens were present in each season, with 81 to 92% of the queens inseminated. While queens were fecund yr-round, the lack of brood production in winter may indicate a curtailment of colony foraging to feed queens and larvae which could impede the strategy of baiting queens consolidated in winter nest sites.

The tawny crazy ant, Nylanderia fulva (Mayr) (Hymenoptera: Formicidae), develops extremely large populations that dominate landscapes and invade buildings in states along the Gulf of Mexico (Florida, Alabama, Mississippi, Louisiana, and Texas), Georgia, and the island of St. Croix, US Virgin Islands (Klotz et al. 1995; Wetterer & Keularts 2008; MacGown & Layton 2010; Gotzek et al. 2012; Wetterer et al. 2014; Gochnour et al. 2019). There is evidence that populations of N. fulva throughout the USA form a single supercolony (Eyer et al. 2018; LeBrun et al. 2019; Lawson & Oi 2020). Control of invasive ants, such as N. fulva, requires a thorough understanding of their biology to guide the development of effective measures of suppression or eradication. For example, phenology and annual population abundance cycles may be used to determine optimal treatment application times (Markin 1970; Hoffmann et al. 2011; Hoffmann 2015). Examining the seasonal prevalence of N. fulva reproductives, Oi (2020) reported the presence of numerous queens within nests during the winter, but curiously these nests contained minimal amounts of brood. To further understand these observations, this study examined the seasonal reproductive status of N. fulva queens collected in north central Florida.

The reproductive status of N. fulva queens was determined by estimating the number of eggs, or large developing eggs, observed in their ovaries and examining spermathecae for sperm. Three N. fulva colonies, or more appropriately called colony fragments because of its supercolony status, were collected monthly from 2 sites in Gainesville, Florida, USA (a private residence [29.6302°N, 82.4638°W]; and a wooded area near Petra Design Inc. [29.7001°N, 82.3335°W]), from Sep 2013 to Feb 2015. Colony fragments (hereafter colonies) were extracted from isolated (> 5 m apart) decaying branches found on the ground and from nested plant nursery containers using the methods of Sharma et al. (2019). Ten dealate queens then were separated from each colony and either dissected immediately or frozen live at –80 °C. Ovaries were dissected from 10 queens per colony, and the number of developing and mature eggs in the ovaries of each queen was estimated with a rating scale used for Solenopsis invicta Buren (Hymenoptera: Formicidae) where 1 = no eggs; 2 = 1 to 10 eggs; 3 = 11 to 50 eggs; and 4 = > 50 eggs (Valles et al. 2013). Whereas the fecundity of S. invicta queens is much higher than N. fulva based on oviposition rates (Tschinkel 1988; Arcila et al. 2002; McDonald 2012), this scale could distinguish changes in N. fulva fecundity among seasons. In addition, the spermathecae of queens were examined by microscopy for the presence of spermatozoa to determine if queens were inseminated (Glancey & Lofgren 1985) (Fig. 1).

Ovary ratings and percentage of inseminated queens per colony were determined for each mo, then grouped into seasons. Using temperatures recorded by the Florida Automated Weather Network ( https://fawn.ifas.ufl.edu/) for Alachua County from Sep 2013 through Feb 2015, seasonal categories were determined from the average minimum and maximum daily temperatures (Oi 2020). The months of Dec to Feb had the lowest average daily minimum and daily maximum temperatures of 6.6 °C (range: –4.6–17.8) and 19.1 °C (range: 3.4–28.3), respectively. These mo were designated as the winter season and the succeeding 3 mo intervals comprised the remaining seasons of spring (Mar–May), summer (Jun–Aug), and fall (Sep–Nov).

The association of the frequency of the 4 ovary ratings per queen with the 4 seasons was determined with a 4 × 4 contingency table and chi-square test. Similarly, the association between the 4 ratings and the number of inseminated and number of uninseminated spermathecae was evaluated by chi-square test of a 4 × 2 contingency table (Proc FREQ, SAS Version 9.4, SAS Institute, Cary, North Carolina, USA). Queens with undetected spermathecae were considered to be uninseminated because previously observed uninseminated spermathecae usually were very difficult to discern.

The frequency of the individual ovary ratings was not randomly distributed across seasons (χ2 = 56.129; df = 9; P < 0.0001), where 73 to 91% (n = 90 and 150, respectively) of the queens had ovary ratings ≥ 3 per season (Fig. 2A). Among the 4 seasons, 81 to 92% of the queens were inseminated, indicating a significant preponderance (χ2 = 12.166; df = 3; P = 0.0068) of mated female reproductives throughout the yr. The seasonal distribution of uninseminated queens was 19% (n = 155) and 14% (n = 90) for winter and spring, respectively, and 8% each for summer (n = 150) and fall (n = 126). The association between ovary ratings and the inseminated and uninseminated queens also was not random (χ2 = 81.686; df = 3; P < 0.0001). All 4 ovary ratings were distributed evenly among uninseminated queens, ranging from 20 to 32% (n = 65). In contrast, 89% (n = 456) of the inseminated queens had ovary ratings ≥ 3 (Fig. 2B). Arcila et al. (2002) reared N. fulva queens from larvae in queenless colony fragments consisting of larvae and workers, and thus could be a source of uninseminated queens. However, whether these queens were dealates or alate gynes was not specified.

The combination of high numbers of N. fulva queens with low brood levels in permanent nest sites, and few, small, ephemeral nests during the winter suggested a winter consolidation of colonies (Zenner-Polania 1990; Oi 2020). Because of the lack of brood in the winter nests despite the presence of many queens, it was hypothesized that queens in the winter were unmated and ovaries would have fewer eggs. The results of this study showed that over 80% of the queens had inseminated spermathecae in each season. In addition, ovary rating frequencies for each season were skewed toward the ratings of 3 and 4 (10–50 eggs and > 50 eggs, respectively) indicating that eggs were present in queens throughout the yr.

The percentages of queens with > 50 eggs increased from 26% in winter to a peak of 68% in summer. The occurrence of queens with 10 to 50 eggs declined from 55% in winter to a low of 28% in summer, while queens with < 10 eggs was below 20% for all seasons (Fig. 2A). These trends suggested that egg production increased in queens as the seasons progressed toward the summer. More dramatic changes in ovary status have been reported in other ants such as Dolichoderus mariae Forel (Hymenoptera: Formicidae) where queen ovaries were inactive in Jan but had increasing numbers of eggs in Apr and Jun (Laskis & Tschinkel 2008).

Fig. 1.

Ovaries dissected from Nylanderia fulva queens. (A) Ovary rated as a “2” (1–10 eggs) where the spermatheca is present. (B) Ovary rating of “4” (> 50 eggs).

img-z2-3_140.jpg

Ovaries of N. fulva queens were primed with eggs in the winter, but this did not reflect the absence of brood in nests examined in the winter (Oi 2020). It is likely that the warmer temperatures during spring and summer and the associated increase in food availability, for example, honeydew producing insects (Sharma et al. 2013), will initiate and sustain the production and oviposition of eggs as seen in other invasive ants (Markin 1970; Tschinkel 1993; Abril et al. 2007; Abril & Gomez 2014; Hoffmann 2015). If queens are not actively producing and laying eggs during the winter, their ingestion of food and bait could be minimal and thus limit the impact of the bait on the queens (Collins et al. 1992; Hoffmann 2015). In Argentine ants, the dominant reproductive queens ingested more bait than non-dominant queens allowing the latter queens to survive and potentially allowing colonies to recover (Hooper-Bui et. al. 2015).

Targeting bait applications to winter nesting sites where N. fulva queens have coalesced represents an enticing control strategy. Indeed, removal of winter nests has resulted in temporary suppression of Argentine ants (Diaz et al. 2014), but bait applications are logistically more feasible than excavating nests over large areas. However, given the potential for limited bait ingestion by queens in the winter, it would be prudent to specifically examine seasonal queen development and empirically determine when and how N. fulva queens could be most efficiently controlled.

Truly appreciated was the detailed technical assistance of E. Mena, J. Dietz, and M. Perdomo (all formerly USDA-ARS), and M.Y. Choi (USDA-ARS) for providing training on ovary dissections. Gratitude is extended to J. Hogsette for providing access to an infested site and to S. Valles (USDA-ARS) for his helpful review of the manuscript. Mention of trade names or commercial products in this article are for the information and convenience of the reader and does not imply recommendation or endorsement by the US Department of Agriculture.

Fig. 2.

Percent frequency of Nylanderia fulva queens with specified ovary ratings: 1 = 0 eggs; 2 = 1 to 10 eggs; 3 = 10 to 50 eggs; 4 = > 50 eggs. (A) among seasons (winter: Dec–Feb, n = 155; spring: Mar–May, n = 90; summer: Jun–Aug, n = 150; fall: Sep–Nov, n = 126), and (B) between uninseminated (n = 65) and inseminated (n = 456) queens over all seasons.

img-z3-2_140.jpg

References Cited

1.

Abril S, Gómez C. 2014. Strength in numbers: large and permanent colonies have higher queen oviposition rates in the invasive Argentine ant (Linepithema humile, Mayr). Journal of Insect Physiology 62: 21–25. Google Scholar

2.

Abril S, Oliveras J, Gómez C. 2007. Foraging activity and dietary spectrum of the Argentine ant (Hymenoptera: Formicidae) in invaded natural areas of the Northeast Iberian Peninsula. Environmental Entomology 36: 1166–1173. Google Scholar

3.

Arcila AM, Ulloa-Chacón P, Gómez LA. 2002. Factors that influence individual fecundity of queens and queen production in crazy ant Paratrechina fulva (Hymenoptera: Formicidae). Sociobiology 39: 323–334. Google Scholar

4.

Collins HL, Callcott AM, Lockley TC, Ladner A. 1992. Seasonal trends in effectiveness of hydramethylnon (AMDRO) and fenoxycarb (LOGIC) for control of red imported fire ants (Hymenoptera: Formicidae). Journal of Economic Entomology 85: 2131–2137. Google Scholar

5.

Díaz M, Abril S, Enríquez ML, Gómez C. 2014. Assessment of the Argentine ant invasion management by means of manual removal of winter nests in mixed cork oak and pine forests. Biological Invasions 16: 315–327. Google Scholar

6.

Eyer PA, McDowell B, Johnson LNL, Calcaterra LA, Fernandez MB, Shoemaker D, Puckett RT, Vargo EL. 2018. Supercolonial structure of invasive populations of the tawny crazy ant Nylanderia fulva in the US. BMC Evolutionary Biology 18: 209.  https://doi.org/10.1186/s12862-018-1336-5  Google Scholar

7.

Glancey BM, Lofgren CS. 1985. Spermatozoon counts in males and inseminated queens of the imported fire ants, Solenopsis invicta and Solenopsis richteri (Hymenoptera: Formicidae). Florida Entomologist 68: 162–168. Google Scholar

8.

Gochnour BM, Suiter DR, Booher D. 2019. Ant (Hymenoptera: Formicidae) fauna of the marine Port of Savannah, Garden City, Georgia (USA). Journal of Entomological Science 54: 417–429. Google Scholar

9.

Gotzek D, Brady SG, Kallal RJ, LaPolla JS. 2012. The importance of using multiple approaches for identifying emerging invasive species: the case of the Rasberry crazy ant in the United States. PLoS One 7: e45314.  doi: 10.1371/journal. pone.0045314 Google Scholar

10.

Hoffmann BD. 2015. Integrating biology into invasive species management is a key principle for eradication success: the case of yellow crazy ant Anoplolepis gracilipes in northern Australia. Bulletin of Entomological Research 105: 141–151. Google Scholar

11.

Hoffmann B, Davis P, Gott K, Jennings C, Joe S, Krushelnycky P, Miller R, Webb G, Widmer M. 2011. Improving ant eradications: details of more successes, a global synthesis and recommendations. Aliens 31: 16–23. Google Scholar

12.

Hooper-Bui LM, Kwok ESC, Buchholz BA, Rust MK, Eastmond DA, Vogel JS. 2015. Insecticide transfer efficiency and lethal load in Argentine ants. Nuclear Instruments & Methods in Physics Research Section B–Beam Interactions with Materials and Atoms 361: 665–669. Google Scholar

13.

Klotz JH, Mangold JR, Vail KM, Davis Jr LR, Patterson RS. 1995. A survey of the urban pest ants (Hymenoptera: Formicidae) of peninsular Florida. Florida Entomologist 78: 109–118. Google Scholar

14.

Laskis KO, Tschinkel WR. 2008. The seasonal natural history of the ant, Dolichoderus mariae, in northern Florida. Journal of Insect Science 9: 2.  https://doi.org/10.1673/031.009.0201  Google Scholar

15.

Lawson KJ, Oi DH. 2020. Minimal intraspecific aggression among tawny crazy ants (Hymenoptera: Formicidae) in Florida. Florida Entomologist 103: 247–252. Google Scholar

16.

LeBrun EG, Plowes RM, Folgarait PJ, Bollazzi M, Gilbert LE. 2019. Ritualized aggressive behavior reveals distinct social structures in native and introduced range tawny crazy ants. PLoS One 14: e0225597. doi: 10.1371/journal.pone.0225597 Google Scholar

17.

MacGown JA, Layton B. 2010. The invasive Rasberry crazy ant, Nylanderia sp. near pubens (Hymenoptera: Formicidae), reported from Mississippi. Midsouth Entomologist 3: 44–47. Google Scholar

18.

McDonald DL. 2012. Investigation of an invasive ant species: Nylanderia fulva colony extraction, management, diet preference, fecundity, and mechanical vector potential. PhD dissertation. Texas A&M University, College Station, Texas, USA. Google Scholar

19.

Markin GP. 1970. The seasonal life cycle of the Argentine ant, Iridomyrmex humilis (Hymenoptera: Formicidae), in southern California. Annals of the Entomological Society of America 63: 1238–1242. Google Scholar

20.

Oi D. 2020. Seasonal prevalence of queens and males in colonies of tawny crazy ants (Hymenoptera: Formicidae) in Florida. Florida Entomologist 103: 415–417. Google Scholar

21.

Sharma S, Oi DH, Buss EA. 2013. Honeydew-producing hemipterans in Florida associated with Nylanderia fulva (Hymenoptera: Formicidae), an invasive crazy ant. Florida Entomologist 96: 538–547. Google Scholar

22.

Sharma S, Buss EA, Hodges GS, Oi DH. 2019. Effect of soil treatments for cottony cushion scale (Hemiptera: Monophlebidae) control on Nylanderia fulva (Hymenoptera: Formidicae) survival and trailing activity. Florida Entomologist 102: 202–206. Google Scholar

23.

Tschinkel WR. 1988. Social control of egg-laying rate in queens of the fire ant, Solenopsis invicta. Physiological Entomology 13: 327–350. Google Scholar

24.

Tschinkel WR. 1993. Sociometry and sociogenesis of colonies of the fire ant Solenopsis invicta during one annual cycle. Ecological Monographs 64: 425–457. Google Scholar

25.

Valles SM, Porter SD, Choi MY, Oi DH. 2013. Successful transmission of Solenopsis invicta virus 3 to Solenopsis invicta fire ant colonies in oil, sugar, and cricket bait formulations. Journal of Invertebrate Pathology 113: 198–204. Google Scholar

26.

Wetterer JK, Keularts JLW. 2008. Population explosion of the hairy crazy ant, Paratrechina pubens (Hymenoptera: Formicidae), on St. Croix, US Virgin Islands. Florida Entomologist 91: 423–427. Google Scholar

27.

Wetterer JK, Davis O, Williamson JR. 2014. Boom and bust of the tawny ant, Nylanderia fulva (Hymenoptera: Formicidae), on St. Croix, US Virgin Islands. Florida Entomologist 97: 1099–1103. Google Scholar

28.

Zenner-Polania I. 1990. Biological aspects of the “Hormiga Loca,” Paratrechina (Nylanderia) fulva (Mayr), in Colombia, pp. 290–297 In Vander Meer RK, Jaffe K, Cedeno A [eds.], Applied Myrmecology, A World Perspective. West-view Press, Boulder, Colorado, USA. Google Scholar
David Oi "The Seasonal Reproductive Status of Tawny Crazy Ant Queens (Hymenoptera: Formicidae) in Florida," Florida Entomologist 104(2), 140-142, (16 August 2021). https://doi.org/10.1653/024.104.0211
Published: 16 August 2021
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