FABULOUS - Stupendous jaw length and nice sharp teeth as diamond sharp pyramids. The hairs on the jaws are sensors that help this aggressive hunter to be more effective. She may be an effective hunter, but she is also a caring mother.

Almost all animals have teeth and jaws to be able to eat food, chew it up into small pieces and digest it. In humans we no longer use our teeth to capture and kill prey because we are now civilised, but in the wild an animal (lions, crocodiles, sharks) that does not (yet) have the ability to reason, must be equipped through millions of years of evolution to survive autonomously. The design of the jaws (or mandibles) of an insect are therefore crucial if they are to exploit their ecological niche.

In this article we'll be looking at the design of a set of jaws some 500mm (20") long. We'll also be comparing the jaws of our robot ant to those of other ant species on this page, where some of those evolved are stunning creations, that nature produces in abundance - nature is like millions of teams of design engineers all over the world constantly looking to improve their product.

This is not limited to planet earth of course. Alien life is a statistical certainty. We would though have to be extremely lucky to meet another advanced life-form, given the millions of years we have taken to evolve - and taking into account that we will more than likely be extinct sooner than we might have been, if we don't stop climate change. Robots might then play a more important role in preserving what we are now, for future advanced life-forms to learn about us. For this reason, our next robot research project may be a lifelike humanoid.

BARGAIN ACTUATOR - It involves a degree of sourcing and engineering, but hand drills convert nicely to make some high output servos. Cordless drill motors are great to drive larger robots around. The planetary gearbox gives lots of torque, but the limiter will need to be locked using a hack - or slippage will occur.

OPEN WIDE - You can see from the CAD plot above that the jaws open to 19" (490mm) from a 10" (250mm) input lever - almost a 50% mechanical disadvantage. In other words we've had to revise the ratios a little. We cannot make 60 pounds (27kg) of closing force at the tips without introducing more reduction gearing. Inefficient though it may be, our bargain servo will drive a 14mm x  2mm screw thread into threaded swivel blocks on either inboard end of the jaws, via a 3:1 reduction, multiplying our 40 lbs of force x 3 (minus losses) to give around 120lbs (54kg) of crushing strength. Some of you may have noticed that the head articulation is exactly the same 3 axis arrangement as a human arm - from the shoulder to the elbow, though why all the fascination with humanoids when humans cannot perform anywhere near as well as other animals. Please note that this frame is Design Copyright and that this photograph is Copyright © Jameson Hunter Ltd 20 December 2015. All rights reserved. You will need permission from Jameson Hunter to be able to reproduce it. 

HEAD SERVOS - By comparison to the heavy duty RC servos used in most robot kits, the above units provide some serious grunt. They will take 12-24 volts without harming the motors - rpm is a product of voltage, so speed rises with voltage. [LEFT] The motor is a Mabuchi 540 frame driving through a reduction gearbox with steel gears. Two of these will provide head left (shake) and right and up and down (nod)  [RIGHT] This is a similar motor from a battery hand drill. The epicyclic gearbox has been hacked, removing the clutching spring and ball bearings that are used to dial in variable torque for driving screws, etc. You can lock the drive by securing the steel outer gear casing to the plastic drill casing. We've inserted a liner that is a tight interference fit. When taking these units apart, be sure to do so in a large bowl or other contained area, or you will lose some of the ball bearings from the front thrust bearing. Clean and re-lubricate on re-assembly.

EPICYCLIC GEARS - Planetary gear trains provide high power density in comparison to standard parallel axis gear trains. The load in a planetary gear train is shared among multiple planets, greatly increasing torque capability, making the gearbox lighter. The more planets in the system, the greater the load ability and the higher the torque density, but also the higher the energy losses - in this case around 15% to be added to the 35% motor losses - and that is why servo based robots are not as efficient as they might be. A move to dc brushless motors for RC servos would be a giant leap forward. The motors shown here are inefficient brushed units - for the sake of economy.

Efficiency losses in a planetary gear train is in the range of 3-6% per stage dependent on proper configuration, compared to a chain drive that loses about 2-3% per stage (98% efficient). But this type of gearbox is compact, with reasonably low mechanical losses - provided that such a unit is well lubricated. We are great fans of proper lubrication. Go with helical gears if you want a gearbox to run as smoothly and quietly as possible, but beware the additional losses. Choose spur gears when you need to maximize the gearbox's torque density or working life under higher loads. Needle roller bearings improve efficient. Hand drill units don't have ball or needle bearings as a rule.

HEAD & JAWS - The head and jaw parts placed in roughly the right position. The neck bearings on the right need to be joined (welded) and mounts made for all three of the servos. The jaws (shown here as a cardboard pattern) need to be made in steel and composites. At the moment we're using 18mm spherical rod ends for the jaw main bearings to cope with 120 lbs of closing power and the ability to lift a person into the air. There are a lot of levers and control rod couplings to make - and some more mountings that sit on top of the head frame, for the antenna. The jaw motor drives a threaded bar that opens and closes the mandibles, further reducing the drive ratio, and so increasing closing torque. Please note that this frame is Design Copyright and that this photograph is Copyright © Jameson Hunter Ltd 2 January 2016. All rights reserved. You will need permission from Jameson Hunter to be able to reproduce it. 

CHRISTMAS PROJECT - ROBOTIC CHALLENGE

The jaws could be made of GRP and leave it at that, but for the fact that this animatronic will also be used for stunt work. For that reason we need a performance pair of jaws. Jaws that can at least slice through plastic and cardboard (and possibly simulated meat) without harming any actors.

The problem is that jaws sharp and strong enough to cut soft materials will also main human actors unless precautions are taken. We are thinking that the sharp jaws will have protective covers fitted when filming actors. The teeth in "Bruce", the animatronic shark in "Jaws" the movie, were soft and flexible - because they were not intended to perform.

The previous frame for the head was a complex design made from sheet metal to form an incredibly strong box with hinges at the front for the jaws and a special dual-axis neck joint. This design was expensive and complex, when the design brief here is simplicity and affordability. For that reason we are replacing the monocoque design with a simple "T" frame made from two lengths of 50mm and 40mm steel box section (RHS). The "T" at the mouth end of the robot, carries a hinge at either end, into which the jaw sections are fitted. It will take more than a couple of (model radio control) jumbo servos to operate the jaws. We are thinking epicyclic gearbox and brushless motor to generate around 92ft/lbs of torque (125Nm).

LEVERAGE - Think of when you first sat on a see-saw, great fun wasn't it? If you were heavier the other swinger went up in the air. if they were heavier, you shot up. That was with the pivot point of the see-saw in the middle. If we move the pivot point, then if you were M1 in the picture above (and heavier) you could move M2 a greater distance using the mechanical advantage (a) compared to the distance (b). Levers can work either way as in the bicycle below.

LEVERAGE - [LEFT] the gear is low (1st) providing good acceleration and traction up hills. [RIGHT] the gear is high (5th) providing a higher speed, having accelerated through the gears.

One foot-pound force = 1.35581794833 newton-meters. The SI derived unit for energy (work done) is the joule. 1 joule is equal to 1 newton meter, or 0.737562149277 foot-pounds of force. The force applied at the cutting tips of our robot jaws with a motor/gearbox providing 92ft/lbs of torque, will be 60 pounds (27kg). More than enough for our purposes, without resorting to hydraulics - though we could easily double the force by using 2 motors. To put this into perspective, many of the new 18 volt cordless hand drills generate 125Nm of torque - and that is why these units are popular with roboteers. You will only get this kind of grunt with the latest dc brushless units - hence, shop around for parts if going DIY.

LEVERAGE

A lever allows us to increase a force applied. The amount of increase is known as the Mechanical Advantage Ratio. A crowbar is a good example of a leverage tool used to amplify the force that a human can apply to open a packing crate. A crowbar is a simple tool consisting of one piece of steel. Other mechanical devices or machine systems may use many levers or cogs of different sizes (gears) to achieve what the engineer wants to do. The gearbox on a car is in effect a revolving lever system where the ratio can be changed by the operator in real time to speed up a vehicle, or climb steep hills.

UGLY MOTHER - Natural efficiency in design can appear ugly at first sight, but once appreciated, that super efficiency can be interpreted as beauty. The jaws of a bulldog ant are super fit for purpose. The unmodified original of this picture was taken by Alexander Wild, according to Lisa Patten of Quantum Leap in Rome. We are reviewing the work of high profile insect photographers, where capturing images of insects is important work for entomologists.

USEFUL FORCE CONVERSION TABLE

NEAT - Not all ants have huge jaws. These are much smaller than some on this page, but they are sharp. Note that one tooth (hardened end of the mandible) on the right is chipped. These are not combat or hunting jaws, they are more general tools for living.

DINO ANT - Dino ponera is one of the world's largest ants. We like the black colour scheme and all rounder design of its mandibles.

ARMY ANTS

These ants are famous for the enormous jaws of their soldier caste. The name army ant (or legionary ant or marabunta) is applied to over 200 ant species, in different lineages, due to their aggressive predatory foraging groups, known as "raids", in which huge numbers of ants forage simultaneously over a certain area.

Another shared feature is that, unlike most ant species, army ants do not construct permanent nests: an army ant colony moves almost incessantly over the time it exists. All species are members of the true ant family, Formicidae, but several groups have independently evolved the same basic behavioral and ecological syndrome. This syndrome is often referred to as "legionary behavior", and may be an example of convergent evolution.

TUSKS - More like the tusks of an elephant than the jaws of an ant, but these handed barbs make a brilliant suture if you happen to cut yourself in the bush.

Most New World army ants belong to the subfamily Ecitoninae, which contains two tribes: Cheliomyrmecini and Ecitonini. The former contains only the genus Cheliomyrmex, whereas the latter contains four genera: Neivamyrmex, Nomamyrmex, Labidus, and Eciton. The largest genus is Neivamyrmex, which contains more than 120 species; the most predominant species is Eciton burchellii; its common name "army ant" is considered to be the archetype of the species. Old World army ants are divided between the Aenictini and Dorylini tribes. Aenictini contains more than 50 species of army ants in the single genus, Aenictus. However, the Dorylini contain the genus Dorylus, the most aggressive group of driver ants; 60 species are known.[citation needed]

Originally, the Old World and New World lineages of army ants were thought to have evolved independently, in an example of convergent evolution. In 2003, though, genetic analysis of various species suggests that they all evolved from a single common ancestor, which lived approximately 100 million years ago at the time of the separation of the continents of Africa and South America. Army ant taxonomy remains in flux, and genetic analysis will likely continue to provide more information about the relatedness of the various taxa.

SOCIAL FOLLOWING - SYMBIONTS

Many species of army ant are widely considered to be keystone species, due to the high number of vertebrate and invertebrate associates that rely on army ant colonies for nutrition or protection. During their hunt, many surface-raiding army ants are accompanied by various birds, such as antbirds, thrushes, ovenbirds and wrens, which devour the insects that are flushed out by the ants, a behavior known as cleptoparasitism. A wide variety of arthropods including staphylinid beetles and mites also follow colonies. The Neotropical army ant Eciton burchellii has an estimated 350 to 500 animal associates, the most of any one species known to science. Imagine if they had a Twitter or Facebook account.

ARMY ANTS - All the mechanical features of other ants, but a huge set of mandibles.

DORYLUS

Dorylus, also known as driver ants, safari ants, or siafu, is a large genus of army ants found primarily in central and east Africa, although the range also extends to tropical Asia. The term siafu is a loanword from Swahili, and is one of numerous similar words from regional Bantu languages used by indigenous peoples to describe various species of these ants. Unlike the New World members of the former subfamily Ecitoninae (now Dorylinae), members of this genus do form temporary anthills lasting from a few days up to three months. Each colony can contain over 20 million individuals. As with their New World counterparts, there is a soldier class among the workers, which is larger, with a very large head and pincer-like mandibles. They are capable of stinging, but very rarely do so, relying instead on their powerful shearing jaws - this is the bit we are interested in.

Such is the strength of the ant's jaws that, in East Africa, they are used as natural, emergency sutures. Various East African indigenous tribal peoples (e.g. Maasai moran), when suffering from a gash in the bush, will use the soldiers to stitch the wound by getting the ants to bite on both sides of the gash, then breaking off the body. This use of ants as makeshift surgical staples creates a seal that can hold for days at a time, and the procedure can be repeated, if necessary, allowing natural healing to commence.

DOOR SHUT - Snapped shut, this is what the jaws of a trap-jaw ant look like. A fabulous picture by Oscar Blanco using a Nikon D80, Nikkor 60mm micro, Raynox DCR-250, Nikon PB-5 bellows, 2x Teleconverter at around 9x magnification. The area of photo is about 2mm. Nice one Oscar.

THE GUARDIAN MAY 2015 - GREAT ESCAPE

Many modern ants Trap-jaw ants are known as fast biters, but researchers have proved that their astonishing leaps, propelled by 140mph muscle movements, are an escape tactic.

They have the fastest bite in the animal kingdom, but the trap-jaw ants’ explosive mandibles also serve a less violent purpose, according to scientists. The insects regularly use their spring-loaded jaws to perform “escape jumps” when face-to-face with a predator.

The ant’s jaws open to 180 degrees before snapping shut at more than 60 metres per second (140 miles per hour). The whole action takes place 2,300 times faster than the blink of an eye.

Previously, the insects had observed jumping with their jaws, but until now it was not clear whether this was an intentional exit strategy or they were accidentally sending themselves flying while trying to land a snap on an aggressor.

Fredrick Larabee, an entomologist who carried out the work at the University of Illinois, said: “It was unknown whether this behaviour was meant to help them get away from a predator, and it wasn’t clear that it actually improved their odds of surviving an encounter with a predator.”

SOLDIER ANT - Who needs eyes when you have jaws like this? Incredible though it may seem, this is an ant that is so specialized that eyes are a hindrance to the defence function. Might that be because a head without eyes is considerably stronger.

To investigate, Larabee and colleagues placed the trap-jaw ant (Odontomachus brunneus) head-to-head against the pit-building antlion, one of its natural predators.

The antlion’s hunting strategy involves digging a conical pit in the sand, burying itself at the bottom and waiting for a victim to fall in. They throw sand at their target, causing tiny landslides, hurrying the progress of their victim to the bottom of the pit, where they are dragged beneath the surface and consumed.

Larabee dropped trap-jaw ants into antlion pits in the lab to test whether they used the jaw-jumping manoeuvre to flee. The ants normally tried to run up the sides of the pit – sometimes successfully – but if that strategy failed, they jumped with their jaws.

“The ants were able to jump out of the pits about 15% of the time in their encounters with antlions,” Larabee said.

When the scientists glued the ant’s mandibles shut before dropping them in the pits, they couldn’t jump at all and it cut their survival rate in half compared to control ants who had glue applied without it closing their jaws.

Larabee acknowledges that the experiment belongs to the scientific school of “doing silly things to animals to figure out what they’re doing”. But simple experiments such as these can give real insight into animal traits and why they evolved in the first place, he added.

“As an entomologist it’s almost a rite of passage to throw insects into these things [antlion pits] and watch them get eaten,” said Larabee. “They’re such charismatic creatures.”

The enormous power of the trap-jaw ant’s mandibles comes from a pair of large, contracting muscles in the head. The muscles work on a latch system, which allows all their stored elastic energy to be released in one go – like a crossbow being fired – generating an explosive force.

Other studies by the same team also suggest that the accidental jump is distinct from the “escape jump” because in the latter case the ants adopt a different stance, lowering their head and raising one leg before making the snap to direct more of their movement vertically.

Prof Andrew Suarez, a co-author and head of animal biology at the University of Illinois, said: “When they were jumping off a surface, you would often see the ants put their entire face against the surface, and it was more of a pushing behaviour than a striking behaviour.” The study is published in the journal PLOS One.

TRAP DOOR - These are the jaws of the famous escape artist, wide open. Though large and powerful, these jaws act like a giant spring to propel the ant away from danger.

TRAP JAW ANT

Odontomachus bauri is a species of ponerinae ant known as trap jaw ants. The trap jaw consists of mandibles which contain a spring-loaded catch mechanism.

This mechanism permits the ants to accumulate energy before striking or releasing the mandibles rapidly. O. bauri is known for its powerful mandibles, which can open up to about 180° and within 10 ms of being stimulated and can close within 0.5 ms, which help with catching prey. The mandibles are able to sting and paralyze prey or crush prey to death. O. bauri also uses its mandibles to propel itself or prey off of the ground either vertically or horizontally. O. bauri can travel over 20 times their body length in a single jaw-propelled leap. To put this extraordinary ability in relative terms, a human would have to be able to throw its body 13 meters high or 40 meters long to match up to the O. bauri’s jumps. O. bauri is closely related to the genus Anochetus which is in the same family, Formicidae. It has been discovered from southern Costa Rica throughout tropical South America, the West Indies (excpet Cuba and Bahamas), and on the Galapagos Islands.

FIRE ANT - Small jaws and eyes, but a painful sting. Fire ant is the common name for several species of ants in the genus Solenopsis. They are, however, only a minority in the genus, which includes over 200 species of Solenopsis worldwide. Solenopsis are stinging ants and most of their common names reflect this, for example, ginger ants and tropical fire ants. Many species also are called red ants because of their light brown colour, though species of ants in many other genera are similarly named for similar reasons. Examples include Myrmica rubra and Pogonomyrmex barbatus.

The colloquial names for several species of weaver ants in the genus Oecophylla in Southeast Asia include "fire ants" because of their red color and painful sting; the two genera, however, are not closely related. Also, Wasmannia auropunctata is commonly called the "little fire ant."

The mandibles of O. bauri are an exaggerated form of the sturdy and long mandibles found in many ant species. Additionally, the muscles found in the mandibles of O. bauri are found in other ants, although those found in O. bauri are large and look very similar to those found in cicadas.

To use correct evolutionary terms, the mandibles and the muscles found in the mandibles are known as exaptation. Exaptations are useful traits that were not originally produced by natural selection for their current use. For example, the large mandibles were selected for in order to help the ants become better able to carry food, but then the ants were able to use these mandibles as a way of defense and for hunting.

ANT EXPERT DUNN LAB - Daniela Magdalena Sorger, PhD says that she is fascinated by ants: "I study their natural history, taxonomy, distribution, behavior, and life history traits. "My research focuses on trap-jaw ants in the genus Odontomachus that live in the United States and tropical places like Costa Rica, Borneo, and the Philippines. I mainly focus on elucidating their phylogeography and population genetics. I am also interested in broad-scale geographic patterns in functionally relevant and conspicuous ant traits, be they physiological (thermal tolerance), morphological (trap-jaws, spines), or behavioral (drumming). Ants are my life and I love to talk about them and explain my research, especially to non-scientists, as I regard communicating my work to the world around me as an essential part of being a scientist."

Daniela graduated from business school with an MSc in International Business Administration in 2008. Three years later she determined to study ants for the rest of her life. She worked for two years at the Natural History Museum in Vienna, a year of basic biology classes at the University of Vienna, a trip to Guatemala and Borneo. She is a biologist who enjoys exploring the tropics, chasing around ants in the jungle and trying to answer exciting science questions.

BITTEN BY THE BUG - How did this happen after all that business background? She says that: "Honestly, I don’t know. I fell in love with ANTS, randomly. No background in biology, no particular science exposure when growing up, nothing that could have suggested this sudden change in life focus." That is not all that unusual, it happened to us, we are also fascinated by the little chaps - more from an engineering point of view, but still there is the biology that one cannot but admire.

Daniela is an evolutionary ecologist. For her, ants are not just a study organism but rather the source of a great passion. After spending a few years at the Natural History Museum in Vienna and field trips to Guatemala and Borneo, she found herself in North Carolina in 2010. Her research encompasses phylogenetics, population genetics, and behavior of ants in Florida, Ethiopia, and Borneo.

CONTACTS: Department of Applied Ecology, North Carolina State University, 127 David Clark Labs, Box 7617, 100 Eugene Brooks Ave., Raleigh, NC 27695, USA. Tel: +1 919-513-7464

Emails:    dmsorger@ncsu.edu    dm.sorger@gmail.com

http://robdunnlab.com/people/d-magdalena-sorger/

https://www.linkedin.com/in/daniela-magdalena-sorger-1a361879
https://twitter.com/MagSorger

There are other ants with killer jaws such as the Strumigenys, Mystrium, Myrmoteras and Anochetus to name a few other ants within the same family with the same features. One commonly accepted theory suggests that the trap-jaw actually evolved independently at least four different times in ants’ history. This is because with the use of DNA sequencing, the phylogenetic tree which found that those ants with trap-jaws were not nested neatly in one portion of the tree. Instead they were found scattered around the tree. Therefore, it did not evolve once leading to the hypothesis of a common ancestor. Instead it evolved multiple times and each time it evolved it used a different feature of the ant’s mouth to produce the trap jaw. For instance, O. bauri’s trap jaw is built from the mandible joint; however, Strumigenys trigger is built from it upper lip. This type of evolution would be deemed as convergent evolution and the trap jaw would be considered an analogy. This is because they are all similar features but involved independently rather than a common ancestor.

BULLET ANT - The pain caused by this insect's sting is purported to be greater than that of any other hymenopteran and is ranked as the most  painful according to the Schmidt sting pain index, given a "4+" rating, above the tarantula hawk wasp and, according to some victims, equal to being shot, hence the name of the insect. It is described as causing: waves of burning, throbbing, all-consuming pain that continues unabated for up to 24 hours. The JCB like jaws remind us of an earth moving scoop.

TIGER BEETLE JAWS - The fastest insect on land also has a hefty pair of mandibles. This animal sucks in another insect, such as a fly, and extracts the fluids, expelling the solids such as the shell. The digestive system is thus also high performance, in not wasting energy breaking down solid matter. Rather, the mouth is a superb design, doing most of the preparation work for the stomach.

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