Featured Research

from universities, journals, and other organizations

Predatory beetles eavesdrop on ants' chemical conversations to find best egg-laying sites

Date:
August 3, 2012
Source:
University of Michigan
Summary:
Predatory beetles can detect the unique alarm signal released by ants that are under attack by parasitic flies, and the beetles use those overheard conversations to guide their search for safe egg-laying sites on coffee bushes.

An Azteca ant grabbing an adult lady beetle on a coffee plant in Chiapas, Mexico. Lady beetles attempt to eat the green coffee scale insects guarded by the ants. But patrolling ants will attack and kill adult beetles and will remove beetle eggs laid on ant-tended coffee plants.
Credit: Photo by Ivette Perfecto

Predatory beetles can detect the unique alarm signal released by ants that are under attack by parasitic flies, and the beetles use those overheard conversations to guide their search for safe egg-laying sites on coffee bushes.

Azteca instabilis ants patrol coffee bushes and emit chemical alarm signals when they're under attack by phorid flies. In an article published online July 27 in the journal Ecology and Evolution, University of Michigan researchers and their colleagues show that pregnant lady beetles intercept the ants' alarm pheromones, which let the beetles know that it's safe to deposit their eggs.

The findings, which may have practical implications for pest management on coffee plantations, are the first documentation of a complex cascade of interactions mediated by ant pheromones, according to the authors.

"It is too often the case that pest management in agriculture focuses on finding a magic bullet solution to every problem," said U-M ecologist Ivette Perfecto, professor at the U-M School of Natural Resources and Environment and co-author of the Ecology and Evolution paper.

First author of the paper is Hsun-Yi Hsieh, a graduate student at the School of Natural Resources and Environment.

"This research shows that there are very complex ecological interactions that are involved in population regulation, and when the population of concern is a potential pest species, understanding those interactions is key to the long-term sustainability of pest control strategies," Perfecto said.

Ants and other social insects communicate using chemicals called pheromones. Little is known about insects and other creatures that exploit ant chemical communication systems. A few such cases have been reported, including ant-eating spiders that use ant alarm pheromones to find their prey and parasitic flies that use ant alarm or trail pheromones to find their host.

But complex relationships involving ant pheromone-mediated interactions between multiple species of insects have not been previously reported, according to Perfecto.

The cast in this bug-world drama features four main players: the aforementioned Azteca instabilis ant, a tiny insect called the green coffee scale, the predatory lady beetle, and the parasitic phorid fly.

Tree-nesting Azteca ants enjoy a mutualistic relationship with the green coffee scale, which is a coffee pest. The ants protect the scale insects from predators and parasites and in return collect honeydew, a sweet, sticky liquid secreted by the green coffee scale.

The lady beetle eats the scale insects tended by the ants. However, patrolling ants attack and kill adult beetles and remove all beetle eggs laid bare on ant-tended coffee plants.

To get their offspring into food-rich patches among the scale insects, female lady beetles hide their eggs in out-of-the-way places -- including the underside of the flat-bodied scale insects. That way, when the beetle eggs hatch they can start eating scale insects immediately, while still being protected from ant predation. A short time later, lady beetle larvae develop a waxy, filamentous coat that offers further protection from ants.

Phorids are a family of small, hump-backed flies resembling fruit flies. The parasitic phorid flies that attack Azteca ants lay their eggs on the ant's body. Fly larvae develop inside the ant's head, which falls off when the adult fly emerges. Phorids need to see movement to detect individual ants; therefore moving ants, rather than stationary ones, are their targets.

Needless to say, the ants do their best to avoid becoming phorid-fly victims. When the flies attack, the ants release a phorid-alert pheromone to warn other workers in the vicinity. In response, nearby ants enter a motionless, catatonic state and overall colony activity declines by at least 50 percent. This effect can last up to 2 hours.

In the Ecology and Evolution paper, Hsieh, Perfecto and their colleagues show that female lady beetles -- especially pregnant ones -- detect the phorid-alert pheromone and take advantage of the ensuing lull in activity to search out safe egg-deposition sites with plenty of food for their offspring. Interestingly, male beetles did not respond to any of the ant pheromones.

For the study, beetles, ants and phorid flies were collected from an organic coffee plantation in the southern part of the state of Chiapas, Mexico, or were reared in the laboratory after field collection from the same site. The insects were placed in a multi-chambered apparatus called an olfactometer, which is used to measure an organism's sensitivity to various odors.

In addition to several olfactometer tests, an egg-deposition experiment was conducted. Pregnant lady beetles were placed in a one-liter container holding a coffee branch with four to six leaves infected with scale insects, 40 Azteca worker ants, and two or three phorid flies. After 24 hours, the coffee branch was removed and examined under a microscope for beetle eggs.

Results of the various tests support the hypothesis that female beetles use the phorid-alert ant pheromone to exploit low ant-activity periods and to locate sites where eggs can be hidden and protected against ant predation after ants resume their normal activity levels.

The authors suggest that such complex interactions may be common in nature, "and their uncommon occurrence in the literature is the product of investigators failing to search for them in the first place."

The results have important implications for the management of the scale insect on coffee plantations. The findings suggest that the conservation of Azteca ants, rather than their elimination, is the best management option, Perfecto said.

"This is counterintuitive because the ants protect the scale insects," Perfecto said. "However, the ants are distributed in a patchwork on the plantations, and the patches of Azteca are essential for the survival and reproduction of the predatory lady beetle."

The patches of Azteca, which cover 3 to 5 percent of the plantation area, act as a source of adult lady beetles, which can help control the scale insects on the rest of the plantation. Since the Azteca ants nest in trees that are planted alongside the coffee for shade, eliminating these shade trees can result in the elimination of one of the most important predators of the scale insects, Perfecto said.

In addition to Hsieh and Perfecto, authors of the Ecology and Evolution paper are Heidi Liere of the University of Wisconsin and Esteli Soto Jimιnez of the Universidad Autσnoma de Chapingo in Mexico. Funding for the work was provided by the National Science Foundation and U-M's Rackham Graduate School.


Story Source:

The above story is based on materials provided by University of Michigan. The original article was written by Jim Erickson. Note: Materials may be edited for content and length.


Journal Reference:

  1. Hsun-Yi Hsieh, Heidi Liere, Estelν J. Soto, Ivette Perfecto. Cascading trait-mediated interactions induced by ant pheromones. Ecology and Evolution, 2012; DOI: 10.1002/ece3.322

Cite This Page:

University of Michigan. "Predatory beetles eavesdrop on ants' chemical conversations to find best egg-laying sites." ScienceDaily. ScienceDaily, 3 August 2012. <www.sciencedaily.com/releases/2012/08/120803102937.htm>.
University of Michigan. (2012, August 3). Predatory beetles eavesdrop on ants' chemical conversations to find best egg-laying sites. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2012/08/120803102937.htm
University of Michigan. "Predatory beetles eavesdrop on ants' chemical conversations to find best egg-laying sites." ScienceDaily. www.sciencedaily.com/releases/2012/08/120803102937.htm (accessed July 28, 2014).

Share This




More Plants & Animals News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Ebola Virus Threatens West Africa

Deadly Ebola Virus Threatens West Africa

AP (July 28, 2014) — West African nations and international health organizations are working to contain the largest Ebola outbreak in history. It's one of the deadliest diseases known to man, but the CDC says it's unlikely to spread in the U.S. (July 28) Video provided by AP
Powered by NewsLook.com
Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) — Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) — The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) — A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins