Fruit Fly Larvae Use Sugar as Bait to Attract and Devour Ants


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Many trees and bushes in the Cerrado, the Brazilian savanna, have sugar glands to attract ants. Known as extrafloral nectaries, the glands produce beads of nectar that supply a nutrient source for ants.

“The ants gather the nectar and, at the same time, patrol the plant’s leaves against attack by other insects, such as caterpillars, for example. All this is very common. What’s surprising is to see an insect taking advantage of ant-plant mutualism to prey on ants, as does a small carnivorous fly,” stated PauloSergio Oliveira, a teacher of ecology at the University of Campinas’s Biology Institute (IB– UNICAMP) in São Paulo State, Brazil.

The fly discussed by Oliveira belongs to the Drosophilidae household of fruit flies. While studying ant mutualisms in between 2008 and 2013, biologist MayraCadorin Vidal, whose master’s research study was monitored by Oliveira, opted for associates to a personal Cerrado reserve on a farm in the area of Itirapina, a village in São Paulo State.There, they saw small larvae of bugs in some extrafloral nectaries of Qualea grandiflora (Vochysiaceae), a blooming tree local to the Cerrado (regional name pau-terra). The larvae fed upon ants and belonged to an unidentified types of fruit fly.

The scientists put the brand-new types in the genus Rhinoleucophenga and offered it the epithet myrmecophaga (from Greek myrmex = ant, and phagos = devourer). A description by Vidal et al. was released in 2015 in Annals of the Entomological Society of America

In a brand-new paper released in July in the journal EnvironmentalEntomology, Vidal information the approach utilized by larvae of R. myrmecophaga to take advantage of carpenter ants of the genus Camponotus.

The scientists discovered that adult female flies laid single eggs next to nectaries, where the larvae later on hatched. “We began investigating how the presence of these larvae might affect ant-plant mutualism. Initially, we thought the larvae blocked access by the ants to the resource exchanged in mutualism, but we later realized the ants were trapped in shelters built by the larvae,” stated Vidal, presently at Syracuse University in New York (U.S.A.).

Vidal concluded that what she earlier observed and has actually now explained was a distinct predation method. “This exploitation of an ant mutualism is unique. In fact, it’s the first known instance of an agent that takes advantage of a resource offered by a mutualistic partner to attract and eat another partner,” she stated.

The research study was supported by FAPESP by means of the structure’s Research Program on Biodiversity Characterization, Conservation, Restoration & & Sustainable Use ( BIOTA-FAPESP).

Ant trap

During the dry cold weather in the Cerrado, the branches of Q. grandiflora are completely leafless. In the summertime, which is the rainy season, the trees have plenty of green leaves, and their mutualism with ants of the genus Camponotus can be observed.

Sugar beads produced in extrafloral nectaries are used to bugs just in the summer season. In exchange, the plant makes great use of the aggressiveness of the legions of ants that patrol its branches and attack caterpillars, beetles, aphids and other bugs drawn in by its leaves and nectar.

In result, the meat-eating fly has actually gatecrashed this mutualistic relationship. During the development of R. myrmecophaga, its larvae have actually adjusted to make the most of the relationship in between Q. grandiflora and the carpenter ant to take advantage of the latter.

“When the larva hatches from the egg, it climbs up and builds a shelter on top of the sugar gland, where it develops until it becomes an adult fly. The shelter is not just the site of larval development but also a trap to capture ants. Inside the shelter, the larva is always lurking for unwary prey,”Vidal stated.

The larval shelter, she included, has a hole through which the larva presses a bead of nectar from the plant’s gland. This bead is the bait. The larva sits right in the middle of the shelter, which is very sticky.

When a foraging ant goes into to gather the nectar, it ends up being stuck and ultimately passes away of fatigue after having a hard time to escape. The larva then utilizes its 2 mouth hooks to pry open the ant’s exoskeleton and feasts on the contents.

“The larva eats the ant’s insides. We found several empty exoskeletons that were still stuck to the larval shelter. In a few cases, the larvae had also devoured wasps, beetles and flies,”Vidal stated.

Infestation of trees and bushes in the Cerrado is extremely typical, she kept in mind, and 85% of the plants observed in the research study were plagued with R. myrmecophaga larvae. Each plant had 5 larvae usually.

Accordingto Oliveira, the predation of ants is an unusual phenomenon. “Very few animals are adapted to eat ants, which are aggressive,” he stated. “They sting and spray acid. Moreover, they’re social insects, so where there’s one there are always many others, and they all gang up on the enemy until it’s dead. Then, they cut it up and take it back to the nest for food.”

In another research study, released in 2016 in the journal Ecology, Vidal evaluated the impacts of the existence of R. myrmecophaga on trees of the types Q. grandiflora. She discovered that trees on which ants invested less time suffered more damage due to the fact that they were less safeguarded versus herbivores.

Vidal stated she presumed there may be other hitherto unidentified cases of ants being preyed upon while foraging on plants in the Cerrado.

“Both ants and plants with sugar glands are abundant in the Cerrado,” she stated. “The ants constantly visit these plants to feed on their secretions. It’s possible that other specialized eaters of ants may yet be discovered.”

Source: ByPeter Moon|Ag ência FAPESP

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