SCI-TECH

The natural world is full of tricksters. African daisies can imitate flies to trick real insects into attempting to mate with them and depositing precious pollen. Some spiders can scuttle around like ants to avoid trouble. Now, an international team of scientists have observed a blow fly successfully living in disguise among termites–by wearing ‘termite masks.’ The findings are detailed in a study published February 10 in the journal Current Biology.  

A chance discovery

A team of scientists discovered a species of blow fly (family Calliphoridae) whose larvae can infiltrate colonies of harvester termites in the Anti-Atlas mountains of southern Morocco. The research group from the Institute of Evolutionary Biology (IBE) at the Spanish National Research Council primarily studies ants and butterflies. Since the area was a little dry and lacking rainfall, the butterflies were not flying. The team decided to look around for some ants instead and were in for a surprise. 

“When we lifted a stone we found a termite mound with three fly larvae that we had never seen before. The water had probably flooded the deeper layers of the nest and the larvae had emerged onto the surface,” Roger Vila, a study co-author and an evolutionary biologist at IBE said in a statement. “It must be an extremely rare species, because we have made three more expeditions in that area and, despite lifting hundreds of stones, we found only two more flies, together, in another termite mound.”

Put on a “termite mask”

The team took a closer look at the ant’s bodies to see what types of adaptations were unique to this species of blow fly. The larvae of this calliphorid fly use disguise that helps them infiltrate termite mounds. The larvae display a “termite mask” on the backs of their bodies. The mask includes a non-functional head adorned with antennae and palps–forward appendages near the mouth of termites–that are the same size as those of a large harvester termites. They also have two false eyes. These fake peepers are the larvae’s breathing holes.  

“Most termites live several metres deep and have no visual perception,” said Vila. “However, harvester termites come out at dusk to collect grass, so they have functional eyes that the larvae are able to mimic with their spiracles.”

The larvae also use unusual “tentacles” around their bodies that are detailed termite antennae dupes. The team used a scanning electron microscopy to look at the tentacles and saw that they help the larvae communicate with several termites at the same time.

[ Related: Even ants may hold grudges. ]

Spray on a chemical disguise

Everything inside a termite nest is dark, so the termites use their antennae to recognize each other. Their antennae can detect the shape and smell of their siblings, since all members of the nest share a particular scent. If the soldier termites sniff out intruders from other colonies, they will attack and dismember the interlopers. 

To keep from being detected–and likely dismembered–the bowflies mimic the distinctive odour of their hosts. The team’s analysis revealed that the chemical composition of the larvae is indistinguishable from the termites in the colony. This chemical disguise is key to interacting with the termites and benefitting from their communicable nest life. Future studies could determine how they create this unique scent booster.

Make a termite share food

When the team initially found the larvae in Morocco, they were in the termite mound’s food chambers. When they observed the larvae back in a laboratory set up, they saw that they tend to settle in the most populated area of the nest. Here, they actually received constant attention from the termites. While the team couldn’t determine what the larvae were eating, they did observe that the termites appeared to be transmitting food to the larvae using their mouths. 

“The larvae are not only tolerated, but they constantly communicate with the termites through contact with their antenna-like tentacles,” said Vila. “The termites even seem to feed them, although this has not yet been unequivocally demonstrated.”

One of the study’s biggest challenges was the difficulty of keeping the insects in the lab. It involves maintaining colonies of desert termites, who live in very special conditions in the wild. 

“The larvae we studied eventually died without metamorphosing, so there may be elements of the nest and the symbiotic relationship between the termites and the flies that we were unable to transfer to the laboratory. Their diet is currently unknown, and their adult form remains a mystery,” said Vila.

[ Related: Flies with shorter eye-stalks act aggressively because females are less attracted to them. ]

Evolve quickly

According to the team, the relationship between the blow fly larvae and termites appears to be some form of social parasitism or symbiosis. Humpbacked flies and termites have a similar relationship. However, it is adult humpback flies and not the larvae that mimic termites. 

Genomic study also showed that the fly belongs to the genus Rhyncomya. No known species of this genus have this unusual lifestyle or physical traits, so the team believes that this new species must have evolved very quickly.

“This discovery invites us to reconsider the limits and potential of symbiotic relationships and social parasitism in nature,” said Vila. “But, above all, we should realise how much we still do not know about the vast diversity and specialisation of insects, which are essential organisms in ecosystems.”

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