- Author: Ben Faber
It might seem like common sense that a starving animal is more likely to take dangerous risks to obtain food than one with a full belly. But new research from UCLA shows that groups of Argentine ants, who forage boldly when they're well fed, exercise far more caution when they've been deprived of carbohydrates and the risks from competitors are high.
This counterintuitive foraging strategy might contribute to the success of these insects, known as Linepithema humile, an invasive species that displaces native ant populations in California and elsewhere and has become a significant agricultural pest, the researchers said.
Their findings, published in the journal Current Zoology, suggest that the unwillingness of Argentine ants to expose themselves to danger when weakened by hunger could possibly give them a competitive edge over other species by helping to preserve their colonies' foraging capabilities.
“While not foraging may lead to a reduction in food stores when those stores are already low, foraging in a high-risk environment exposes the colony to potential loss of foragers,” said the study's senior author, Noa Pinter-Wollman, a UCLA professor of ecology and evolutionary biology. “So reduced foraging could be interpreted as individual foragers not taking unnecessary risks.”
To support the energetic requirements of daily life, all ants require carbohydrates, which they obtain from a variety of plant and animal sources. They also need protein, which they generally get from dead animals, to nourish their larval offspring. Ant colonies adjust their foraging strategies according to the availability of these food sources, the presence of competing ant species, and the threat of predators or other dangers. Well-fed ants will forage for carbohydrates even in the presence of other ant species or danger cues.
First author Bryce Barbee, who conducted the research as a UCLA undergraduate, expected that starving Argentine ants of either carbohydrates or protein would only increase their willingness to forage for those foods in high-risk environments because they had little to lose and everything to gain.
Together with Pinter-Wollman, Barbee designed a series of laboratory experiments that involved feeding ants normally, depriving them of either carbohydrates or protein, and depriving them of both, then allowing them to forage as they normally would in either low-risk or high-risk environments.
The researchers created the impression of high-risk environments with formic acid, a chemical marker produced by ants, to signal the presence of competitors.
When the risk was low, starving ants did indeed forage more vigorously for the food of which they had been deprived. But when the risk was high, starving ants surprised the researchers by becoming more cautious, not less, in their foraging strategies.
In both high- and low-risk foraging scenarios, the ants were more willing to forage for carbohydrates than protein, which they only need to raise their brood. Since no eggs or pupae were present in the laboratory colonies, this finding might not be surprising, but it could also indicate that starving ants put their own energetic needs ahead of raising offspring, the researchers said.
Scientists who study animal behavior have advanced two ideas to explain foraging strategies. The first, known as the asset-protection principle, holds that hungry animals have less to lose than satiated animals and will therefore behave more assertively to get food. The second, the state-dependent safety hypothesis, holds that animals in good condition are more likely to take risks because they are more likely to survive dangers they encounter.
“Our work upheld the state-dependent safety hypothesis but not the asset-protection principle,” said Barbee, now a doctoral student at UC Santa Barbara. “The findings suggest that factors such as activity level and energetic costs of starvation are important for Argentine ant foraging decisions.”
The work points toward an avenue of research that could lead to better efforts to control the spread of Argentine ants and mitigate their detrimental impact on agriculture, the researchers said.
https://academic.oup.com/cz/advance-article/doi/10.1093/cz/zoac089/6825390
Ant species across five subfamilies exchange milk-like substances. Jasius via Getty Images
![ants feeding ants feeding](https://ucanr.edu/blogs/Topics/blogfiles/96589.jpg)
- Author: Ben Faber
You wanted to see where all those ants are coming from? Well here is the site to see what ants are where with their descriptions and images.
The ant fauna of California comprises 8 subfamilies, 44 genera and approximately 300 species (of which 30 are introduced). About 25% of the native species are endemic to the state or to the California Floristic Province (including northern Baja California and southern Oregon).
https://www.antweb.org/adm1.do?name=California&country=United+States
Prominent California ants include seed-harvesting species in the genera Veromessor, Pheidole and Pogonomyrmex; honeypot ants in the genus Myrmecocystus; a diverse array of species in the genera Camponotus ("carpenter ants") and Formica; native fire ants (Solenopsis spp.); velvety tree ants (Liometopum spp.); and the introduced Argentine ant (Linepithema humile). This last named species is particularly common in urban and suburban parts of California, where it establishes dense populations and eliminates most native species of ants.
This web site provides color images and identification information for most of the species of ants known to occur in California. For identification of pest ants you may find it useful to consult the key to common household ants of California developed by the UC Statewide IPM Program.
Specimens: 15,612
Images: 655
Imaged Specimens: 981
Subfamilies: 8
Genera: 44
Species/Subspecies: 305
Valid Species/Subspecies: 266
Endemic: 26
Introduced: 23
Show All Specimens
https://www.antweb.org/about.do
AND WAIT, THERE"S MORE - ALEX WILD'S SITE HAS EVEN MORE WONDERFUL IMAGES AND HISTORIES OF ANTS
https://www.alexanderwild.com/Ants
Plus a menagerie of other Insect images - https://www.alexanderwild.com/Insects/Portfolio/
Check it out
And if you want to get down with the Argentine Ant. Don't forget the Workshop next week
Argentine Ant Workshop and Registration
David Haviland says the best Ant Costume wins free admission. Actually it's free to all who register for the meetings.
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- Author: Ben Faber
UCCE & UCR Argentine Ant & Citrus Pest Management Field Day
Get Down with Argentine Ants
November 1 – Redlands, CA
November 2 – Saticoy, CA
Mornings: 8-12
Overview of Biocontrol Methods for ACP in Southern California, Mark Hoddle, Entomology and Extension Specialist at UC Riverside, Director of Applied Biological Control Research,
Overview of ACP/HLB Area-wide Spray Programs in Southern California, Sandra Zwaal, Citrus Pest & Disease Prevention Program, ACP/HLB Grower Liaison San Diego, Riverside, San Bernardino, and Ventura Counties,
Then out to the field to see:
Argentine Ants in Citrus at designated stations in small groups
- Discussions and demonstrations of use of hydrogel beads for Argentine ant control and we would cover aspects of ant biology/ecology/behavior/other control options at this station, Ivan Milosavljevic, UC Riverside
- Discussion and demonstration of monitoring programs for Argentine ants with a focus on using infra-red sensors, visual sampling, sugar-water saturated cotton wool balls, and liquid monitoring vials, Mark Hoddle & Michael Lewis, UC Riverside
- Enhancing natural enemies in citrus orchards with the use of cover crops. This station will cover possible species that could be used, aspects of flowering plants that make them good candidates for use in conservation biological control, the types of generalist natural enemies that will respond to these floral resources, and benefits and drawbacks of using cover crops. Nicola Irvin, UC
- The potential for hydrogels across regions, ant species, crops, and active ingredients. Discussion about major ant groups, resources to identify ants, a little about ant biology in the context of making hydrogels work, and then give an update on the results of trials funded by DPR to evaluate hydrogels against different ant species in different crops across California using five different active ingredients. This station will include the Ant ID mini station. David Haviland, UC Cooperative Extension, Kern County
REGISTRATION Acknowledgment Reply will include agenda and directions for the different sites
Contact: Ben Faber, bafaber@ucanr.edu, 805-645-1462
November 1 Location: Carriage House Prospect Park, 1399 Prospect Dr, Redlands CA 92373
November 2 Location: 2641 SP Milling Rd, Saticoy, CA, follow the signs to Rancho Santa Clara del Norte, which is at the end of the road. Watch at turn to SP Milling Rd for traffic on Hwy 118/Los Angeles Ave.
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- Author: Ben Faber
Dr. Hoddle presented about how to monitor and manage Argentine ant in citrus orchards with liquid baiting systems and discussed why ant management has such strong benefits for the suppression of sap-sucking pests by natural enemies. This information is critical for PCAs and growers to better understand why managing Argentine ant is important. (Presentation slides in the PDF format)
From: https://www2.ipm.ucanr.edu/agriculture/citrus/Ants/
There are numerous species of ants present in citrus orchards, however, the most common are the Argentine ant (southern and coastal California), the native gray ant (San Joaquin Valley) and the southern fire ant (statewide). The red imported fire ant has been found in Southern California, but is not yet established in citrus orchards. It is important to identify the primary ant species in the orchard, because management tactics depend on which ant species is present.
The Argentine ant, is a small, uniformly deep brown ant. Worker ants travel in characteristic trails on trees, the ground, or irrigation lines and build their nests underground. Ant populations peak in mid-summer through early fall.
The southern fire ant is light reddish brown with a black abdomen. These ants build nests of loose mounds or craters near bases of trees, do not aggregate in colonies as large as those of the Argentine ant, and will sting and bite.
Native gray ants are gray and considerably larger than the other two species. They nest in topsoil or under rocks and debris and move in irregular patterns. In contrast to Argentine and fire ants, the native gray ant is solitary and its importance in disrupting biological control is often underestimated.
Red imported fire ant is new to California and can make large, dome-shaped mounds. They feed on almost any plant or animal material.
Damage
Most ant species feed on honeydew excreted by various soft scales, mealybugs, cottony cushion scales, whiteflies, psyllids, and aphids. As part of this relationship, they protect these pest insects from their natural enemies, thus interrupting biological control. They also protect some non honeydew-producing pests, such as California red scales.
Argentine and native gray ants are the most common ant species that aggressively protect pest insects. In addition, Argentine ants and fire ants can plug up irrigation sprinklers. Fire ants directly damage citrus by chewing twigs and tender bark of newly planted trees; they also sting people working in the orchard and may cause allergic reactions.
No effective natural enemies of ants are known.
Cultural Control
Skirt prune trees, i.e., remove branches within 12 to 30 inches of the ground, and apply sticky material to the trunk to prevent access to the trees by ants. Use polybutenes, as oil-based materials may cause phytotoxicity and should not be used.
The application of sticky polybutene materials directly to the trunk of citrus trees can cause bark cracking, especially if multiple applications are applied to the same area of the trunk, the area is exposed to sunlight (topworked trees), or both. The sticky material can be applied on top of a tree wrap or a base layer of latex paint. Young trees, which have a very thin cambium layer, are most susceptible to damage.
Sticky material should last from 1 to 4 months and will also prevent the access by Fuller rose beetles. If the sticky material contains tribasic copper sulfate, it will also control brown garden snails. The persistence of sticky material can be increased by applying it higher above the ground to reduce dust and dirt contamination and to decrease irrigation wash-off.
Baits
Argentine ant adults are liquid-feeding only and have physical digestive "blocks" in the mouth and gut to prevent them from swallowing and digesting solid food particles. They may bring back solid food to the colony to feed the brood (but solid-food digestion not been confirmed in Argentine ant brood), or harvest the bodily fluids inside of insect prey/moisture in food items. Dry insects or food items are of little use to them, even though they may pick these things up. Feeding studies have shown ants feed several times faster on liquids than gels and gels than solids. This faster feeding resulted in much higher toxicity with liquid. Gel was intermediate, and solids provided the lowest control.
Put out bait in the shade to increase feeding and overall kill. You do not need to obscure it. The soil temperature and moisture are going to be more moderate in the shade, particularly under the canopy. This is the environment the ants will prefer to feed in. There will be less evaporative loss in the shade, as well. Sometimes when the toxins become too concentrated they are less attractive to the ants. The other issue is that many toxins (like borax products) may photodegrade at a faster rate in direct sunlight.
![aRGENTINE ANT aRGENTINE ANT](https://ucanr.edu/blogs/Topics/blogfiles/73261.jpg)
- Author: Ben Faber
How ants can be “good” in ag production systems
By: Madison Sankovitz, UCR Entomology, Ph.D. Candidate, Purcell Lab, UC Riverside
Ants are often underappreciated in the United States for their natural benefits to agriculture. Organized as predatory superorganisms, ants often play an important role in pest management. Further, their influence extends beyond their pest control abilities; many ants live in soil and play a crucial role in maintaining soil fertility. Although recognized for their aphid-protecting tendencies and thus disliked by many growers, many traits of ants make them not only beneficial insects in agricultural settings but possibly a significant solution for sustainable food production moving forward.
Pest Control
The ability of ants to suppress pest species in an efficient way has been known since the year 300 A.D., and farmers continue to conserve and promote ant populations in agricultural systems in many regions of the world (Drummond & Choate 2011). They eat the larvae and eggs of pests and also disturb them during feeding and oviposition (e.g. López & Potter 2000). Weaver ants Oecophylla spp. (which live throughout Asia and Australia) are arguably the most well-documented ant genus used in biological control, but similar effects may occur in ants worldwide. Weaver ants share beneficial traits with nearly 13,000 other ant species and are unlikely to be unique in their properties as control agents (Offenberg 2015). For example, all ants can store protein in the form of trophic eggs and brood that can be cannibalized (Nonacs 1991), making their colonies stable and predictable service. Similar social and morphological traits in other ant species suggest great potential for the use of native California ants in the control of arthropod pests, weeds, and plant diseases in orchards and arable crops.
Soil Influences
In addition to pest control, ants are important soil agents in agricultural systems because they contribute to aeration and fertilization, leading to higher soil quality. Aeration is the creation of pockets of air in soil, which help nutrients, water, and fertilizers seep into the soil and reach a greater extent of root systems throughout an agricultural plot. Ants aid in this process by digging a labyrinth of tunnels within the soil. Furthermore, ants introduce outside nutrients (e.g. seeds and insects) to the aerated soil through their foraging; food sources brought into the nest by worker ants decay and fertilize the surrounding plants, especially in no-till plots (Lange et al. 2008). For example, one field experiment showed that ants and termites increase wheat yield by 36% from increased soil water infiltration due to their tunnels and improved soil nitrogen (Evans et al. 2011). This result suggests that ants and termites have similar functional roles to earthworms (often regarded as the most important agents of soil turnover in many regions of the world). Additionally, they may provide valuable ecosystem services in dryland agriculture, which will become increasingly crucial for agricultural sustainability in arid climates, as is the case in some parts of California (Evans et al. 2011).
Ants as Indicators
The presence of ants alone can be beneficial for growers; ants have been suggested as effective bioindicators of soil quality, especially in low-income areas that do not have access to expensive soil monitoring equipment (De Bruyn 1999). Growers are being pressured to rectify the issues of land degradation by reforming their management techniques; however, there are few tools to monitor soil health that can reliably inform farmers of the wholistic state of their soil. If ants could be further investigated as accurate bioindicators, they would be valuable tools for use in agricultural practices worldwide.
Future Directions
Through changes in management practices such as tillage and other manipulations of vegetation and crop structure, beneficial ant populations can be conserved in a variety of agroecosystems. However, there is still much research to be done to determine the extent of agricultural services ants provide. Some ant species succeed in defending specific cropping systems, whereas others are damaging and yet others play dual roles. A future challenge is to determine positive and negative ant–crop pairs and to develop management practices that facilitate the positives and remove the negatives. Another possibility for research is to focus on the development of barriers that keep ants in soil and off of crops; this would allow them to carry out their soil services while not tending phloem-feeding insects. Additionally, there is a need for better documentation of ant biodiversity in agricultural soils in many regions of the world, including California. This data will allow for evaluation of ants as bioindicators of soil quality and predictions of the vulnerability of ant species under future changes in land use and climate. If we can better understand species patterns and the multitude of roles ants play in agricultural systems, they can be utilized for more sustainable food production in the future.
References
De Bruyn, L. L. (1999). Ants as bioindicators of soil function in rural environments. In Invertebrate Biodiversity as Bioindicators of Sustainable Landscapes (pp. 425-441).
Drummond, F., & Choate, B. (2011). Ants as biological control agents in agricultural cropping systems. Terrestrial Arthropod Reviews, 4(2), 157-180.
Evans, T. A., Dawes, T. Z., Ward, P. R., & Lo, N. (2011). Ants and termites increase crop yield in a dry climate. Nature communications, 2, 262.
Lange, D., Fernandes, W. D., Raizer, J., & Faccenda, O. (2008). Predacious activity of ants (Hymenoptera: Formicidae) in conventional and in no-till agriculture systems. Brazilian archives of Biology and Technology, 51(6), 1199-1207.
López, R., & Potter, D. A. (2000). Ant predation on eggs and larvae of the black cutworm (Lepidoptera: Noctuidae) and Japanese beetle (Coleoptera: Scarabaeidae) in turfgrass. Environmental Entomology, 29(1), 116-125.
Nonacs, P. (1991). Less growth with more food: how insect-prey availability changes colony demographics in the ant, Camponotus floridanus. Journal of Insect Physiology, 37(12), 891-898.
Offenberg, J. (2015). Ants as tools in sustainable agriculture. Journal of Applied Ecology, 52(5), 1197-1205.
Rüppell, O., & Kirkman, R. W. (2005). Extraordinary starvation resistance in Temnothorax rugatulus (Hymenoptera, Formicidae) colonies: demography and adaptive behavior. Insectes Sociaux, 52(3), 282-290.
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