September 1, 2008

Young Insects Manipulate Parents For Food And Affection

A new study by researchers at the University of Basel's Zoological Institute illustrates the complex nature of the relationship between parent and offspring, even among insects.

The study found that larvae and nymphs actively solicit their parents for food, protection and affection, doing everything from kicking their mother in the face to hitting her with their antennae to get what they want.

The research may hold clues about how such manipulation first evolved in certain species, including humans.

Some of the most effective manipulators and mothers might even be insects, the researchers said.

Flore Mas, a researcher at the University of Basel's Zoological Institute and co-author of an upcoming report about the study, explained how frightened treehopper nymphs aggressively shake their plant habitats to win their mother's attention.  The mothers react accordingly, in order to "protect their offspring by sitting on top of them and repelling the attacker with aggressive behaviors, such as leg kicking, wing fanning or body twisting," she said.

Mas and her colleague Mathias Kolliker examined several such interactions between larvae and their parents.   Perhaps the most extreme manipulation was observed among baby burying beetles and Earwigs, they said.  The larvae kick their parents in the face, stimulating the mother to regurgitate food into their mouths.   Even larvae that live in confining cells, such as Vespidae wasps, often scrape their mandibles on their cell walls to obtain food and attention.

"Manipulation occurs when the emitter has evolved a cue that affects the receiver, but the receiver's response has not evolved to be affected by this cue, so there is no communication," said Mas during an interview with Discovery News.

She said that such signals might convey a true and urgent need. The cues are typically chemical in nature, so when a baby bug is scared or hungry it might emit hormones that convey its fear to its parents.  Although it is typically the mother who responds, fathers of assassin bugs, correid bugs and thrips also help with parental duties.

The top "bug dads" may very well be burying beetles, Mas said.  Since the species feeds on corpses, and the father must guard the dead corpse "home" to guarantee relative freshness for his family.

But the begging can sometimes be dishonest, arising from sibling rivalry or competition between the parent and its offspring.  And bullies exist in the bug world as they do among humans, the researchers found.

"It is possible, and often observed, that actually it is the strongest or the oldest that get the best spot in the nest where parents are feeding, and thus those behaviors positively correlate with competitive ability but not necessarily with true need for food," Mas said.

It may even be in the best interest of the young insects to amass food and parental attention, considering that "the addition of more brothers and sisters does not contribute to its own survival."

"Thus, we expect in offspring selection for traits that will enhance their own chance of surviving, such as begging behaviors that influence the amount of parental care provided by parents," Mas explained.

Recent research on human bullying, such as that occurring in the workplace, is similar to what often happens among insects.

Sarah Tracy, an associate professor of communications at Arizona State University, recently studied victims of workplace harassment.  These workers reported feeling like "vulnerable children". 

"I feel like I have 'kick me' tattooed on my forehead," one victim said.

Mas hopes future research on insects may reveal more about the evolution of such manipulation, which may one day help resolve workplace harassment and other types of human conflicts.

The research will be published in an upcoming edition of the journal Animal Behavior.

Treehopper Image Courtesy Georg Slickers - Wikipedia


On the Net: