March 18, 2021 | Margaret Helder

Trap-Jaw Ants Pose Trick Question

Ant Study Handles Trick Question:
Form or Function: Which Came First?

by Margaret Helder, PhD

Insects are famous for their diversity. Everybody knows that! So it was that when an international team of biologists undertook to study the ant genus Strumigenys, which is globally distributed, they knew what kind of challenge they faced. There are apparently more than 950 species in this genus, which make it the third largest ant genus worldwide in terms of number of species. The team however did not study all of these species, but only 450 of them. Still, that represents a massive undertaking.

What they were really looking for was ideas on how these insects evolved their food catching techniques. First, of course, they had to study the biology of these insects before they could draw any evolutionary conclusions. Thus, they compared the various forms which these creatures displayed in their mouth parts relative to their lifestyles and habitat. They published their findings in PLoS Biology.1

Trap-jaw ant Strumigenys scotti (Wiki Commons)

Setting the Scene

It transpires that these ants live mainly in leaf litter on the forest floor, often in tropical and semitropical regions of the globe. Their food of choice are springtails which are also worldwide in distribution.2 There are two basic designs of these ants. There are those that hide in the leaf litter and grab any passing springtails with their formidable claw like mouthparts called mandibles. These structures are typically triangular-shaped and sometimes enhanced with stinging devices or chemical lures. Those mandibles work pretty fast too, about 5-10 times faster than other insects with similar gripping hunting techniques. Such ants in this genus are found worldwide, but they do not exhibit a lot of diversity in body plans and mouth shape.

The larger and much more diverse group of these ants are the trap-jaw species. They too are found worldwide, but the details of the mouth parts are so different from those on other continents that specialists consider that the innovation of a trap jaw originated entirely separately 7-10 times within the genus. Evolutionists call this phenomenon of separate origins “convergence”, suggesting that different groups of ants settled on similar solutions to the challenge of survival, but from different starting points.

Amazing FactsThe trap jaw is a very sophisticated system for catching prey. These ants actively hunt springtails with mandibles which work in “mousetrap-like fashion”3 with the fastest snapping action recorded for any animal which is able to re-set the device. Indeed, some of these traps close at an acceleration speed hundreds of thousands of times faster than similar traps in other creatures. Naturally these ants are highly successful at catching the elusive springtails. Video clips in an article on SciTech Daily show how the mechanisms work.

Every geographic region exhibits both types of ant in this genus, although the details of the trap-jaw designs differ greatly between one region and others.

Formulating Questions

This team of biologists chose this fascinating group of insects for the challenge of providing an evolutionary explanation for the trap-jaw origins. What they wanted to know was how the dramatically more sophisticated trap jaws came from the simpler gripping jaws (assuming that they did). The trap jaws are sophisticated in form and function. Did the new function appear first, followed by diversification of form (working with what was newly possible with the new function) or did changes in anatomy make possible the new function? Thus, the question they asked was: “whether functional changes occur early and subsequent phenotypic change is driven by selection to explore a new adaptive landscape” or “whether the diversification of forms leads to the evolution of new functions.”4

These scientists considered that there were only two possible answers to the question of origins. Both of these designated answers were evolutionary scenarios, of course. The first scenario suggested that: “if new functions can evolve through minor changes to form and then natural selection can then optimize the same set of mechanical tradeoffs, then we may expect these innovations to happen repeatedly.”5 Alternatively, they declared that if “many precursory changes are needed to ‘discover’ a new function”6 then “any given breakthrough may be so improbable that it is unlikely to be repeated.”7 Such progressive changes in form might be so “fortuitous and idiosyncratic” that “different lineages in different geographic regions are likely to take divergent paths and reach different outcomes.”8 But this is not what they found, rather they found “convergent” designs, not unique ones.

Only One Answer Is Considered

Having drafted these questions as the only choices, the scientists found that they had only one possible answer. The choices had been whether function (ability to snap jaws closed) preceded form (obvious snapping mechanism) or whether the opposite was the case. Thus, their approach to the topic was “By analyzing the global radiation of this ant group, we assess the extent to which the evolution of the mandible diversity was driven by singular evolutionary events versus the repeated evolution of parallel adaptive forms.”9 Having asked this evolutionary question, they had their evolutionary answer. When “we ask if the range of phenotypic variation indicates which occurred first: the diversification of morphology (reshaping of mandible system) or the basic function design of that system (presence or absence of a LaMSA mechanism [latch mediated spring actuation]”10, their answer was that function (the ability to trap) came first, followed by major changes in form.

Their only possible answer given the multiple instances of convergence was that “most morphological diversification occurred after evolution of latch-spring mechanisms, which evolved via minor alignments of mouthpart structures.”11 They concluded that “extremely modest morphological changes can result in the evolution of the latch-spring-actuation mechanism”12 or to put it bluntly, they believed that they had established that there were “subtle morphological changes with large functional effects.”13 Thus, they concluded that the new function appeared multiple times as a result of slight deviations from the ancestral gripping condition. Then natural selection selected more effective variations on the trap-jaw theme and the new sophisticated traps developed.

Thought Experiment

That is what the authors concluded, but there is just one thing wrong with it. Function cannot precede form. The trap-jaw is irreducibly complex. Multiple precise changes to mouth part anatomy have to happen simultaneously for the trap-jaw to function even a little bit. Let us imitate Einstein and conduct a thought experiment on the ants. Which ones will survive?

Ant A – develops projections from its mandibles in an appropriate part of the mouth piece. However, if there are no suitable hooks on the adjacent labrum, the mandibles will never be positioned for the trap. This ant is stuck with the old grip technique, but at least he may survive.

Ant B – assuming there are projections on mandibles, this ant develops a suitable receptor (hook) (in an appropriate position) on the labrum. But the labrum’s role in gripping jaws is to sense prey. With only these innovations, nothing new happens again and the ant merely goes on with its gripping lifestyle. With no reason to select for these changes, the innovations will be lost or selected against as they are a waste of effort.

Ant C – (assuming A and B are in position), we now need new muscles in the labrum. These are able to push the mandibles apart. Also, the labrum has to hold that new position. So, here is Ant C with its mandibles pried wide open, but no release mechanism. “Help!” it cries. This ant will not survive.

Ant D – has its mouth pried open.  It now needs a sensor to detect prey, but it still has no mechanism to unlatch mandibles. Whoops, there went his dinner. He does not survive either.

Ant E – has all of the above. If there is a release mechanism to allow mandibles to close, but no special modifications in head muscles to power up the speed of the snap of the mandibles, the springtails spring free again.  Whoops, there went his dinner too. This ant does not survive.

Ant F – the muscles controlling the mandibles have re-organized their muscle fiber structure from speed optimized action to force optimized action. Only with all these structures in place at the same time, will this ant be able to catch his dinner.

Ant G – all the above changes have to be in place at the same time for the snap jaw to function. If any one of these novelties is missing, the ant will not survive. Natural selection can work only on a fully functioning system to fine tune the details.

So where did the trap jaw ant obtain its highly efficient and rapid prey capturing mechanism? We can see that the system is irreducibly complex. Precise changes to six mouth-related parts have to be in place at the same time for the trap to work. The scientists involved realized that the gradual appearance of such changes is too challenging to realistically occur. Instead, they opted for “minor changes” which allow the system to develop without the tedious process of gradual selection of different parts. What do they mean by minor or subtle changes? Either the trap works or it does not. They suggest that these changes are not too difficult to have happened on 7-10 occasions, to bring about the diverse manifestations of the trap that they found worldwide.

Answer Ignores Evidence

The team admits, however, that their answer of function preceding form does not really explain anything. They declare right away, “However, understanding how transitions in function evolve when they require changes in multiple interacting parts, remains a challenge.”14 More specifically, they declare: “The repeated evolution of similar LaMSA [latch-mediated spring actuation] mechanisms in distant lineages is itself fascinating, yet in no case do we understand how these functional breakthroughs occurred from ancestors lacking a trap mechanism.”15 They do not know how their system could actually emerge.

The published conclusion to the study does not work. Function cannot appear before the physical details in a system. A device that carries out a new task or function is an invention. Douglas Axe, in his book Undeniable: How Biology Confirms Our Intuition That Life is Designed, discusses the nature of biological inventions. He points out that “by the time selection begins to favor an invention, something other than selection has already invented it.”16 He describes how an invention involves many contributing parts working together to produce a function. We indeed saw this in the case of the trap jaw. “What enables inventions to perform so seamlessly is a property we’ll call functional coherence. It is nothing more than complete alignment of low-level functions in support of top-level function.”17 Thus, Dr. Axe concludes: “since the hallmark of invention is functional coherence – which accidental causes can’t explain – we rightly see each form as a distinct masterpiece. Accident is out of the picture…. There is no substitute for brilliance.”18

The authors of the ant project declare in hopeful fashion that their study may point the way to a new general evolutionary theory where new functions appear before major changes in anatomy (form or morphology).19 Of course, they did not find any such thing and they actually have no answer to their evolutionary questions. They even tried to answer the wrong question. They should have asked if evolutionary changes can explain their observations. Can function indeed appear before major changes in anatomy? The answer is obviously “No”. Nothing other than intelligence explains the appearance of the sophisticated trap jaw in these ants. You can attribute the trap jaw phenomenon to intelligent design or to separate creations, but you cannot attribute it to evolution.


1  Douglas B. Booher et al. Functional innovation promotes diversification of form in the evolution of an ultrafast trap-jaw mechanism in ants. PLoS Biology 19 (3): e3001031. 1371/journal.pbio. 3001031.
2  Springtails are tiny arthropods about 1-2 mm long. They have six legs, but are not considered insects because they lack wings. They possess an extension at the tip of the tail which suddenly launches them up to several inches (e.g. 3 inches = 7.5 cm) into the air. Not surprisingly, they are very hard to catch and have few predators, but Strumigenys ants are one such predator. The springtails favor moist leaf litter and so do the ants.
3  p. 2.
4  p. 1. Equivalent to which came first, the chicken or the egg?
5  p. 2.
6  p. 1.
7  p. 2.
8  p. 2.
9  p. 3.
10  p. 1.
11  p. 1, emphasis mine.
12  p. 6, emphasis mine.
13  p. 6 emphasis mine.
14  p. 1.
15  p. 2.
16  Douglas Axe. 2016. Undeniable: How Biology Confirms Our Intuition That Life is Designed, pp. 300. See p. 96, emphasis his.
17  Axe p. 143 emphasis his.
18  Axe p. 193.
19  Booher et al. 6.

Margaret Helder completed her education with a Ph.D. in Botany from Western University in London, Ontario (Canada). She was hired as Assistant Professor in Biosciences at Brock University in St. Catharines, Ontario. Coming to Alberta in 1977, Dr Helder was an expert witness for the State of Arkansas, December 1981, during the creation/evolution ‘balanced treatment’ trial. She served as member of the editorial board of Occasional Papers of the Baraminology Study Group in 2001. She also lectured once or twice a year (upon invitation) in scheduled classes at University of Alberta (St. Joseph’s College) from 1998-2012. Her technical publications include articles in the Canadian Journal of Botany, chapter 19 in Recent Advances in Aquatic Mycology (E. B. Gareth Jones. Editor. 1976), and most recently she authored No Christian Silence on Science (2016) which promotes critical evaluation of scientific claims. She is married to John Helder and they have six adult children.

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