Kind of Confusing – Young-earth Creationist’ Classification of the Bombardier Beetle

Young-earth creationists in the twenty-first century take a broadly inclusive view of the relationship of existing and extinct species as they relate to the kinds of organisms that God created one days four, five, and six of the creation week. For example, the image below is from a new display of the origin of the great apes at the Creation Museum and is representative of Answers in Genesis’ understanding of origin and diversification of kinds. (see also: Chimps, Orangutans, and Gorillas Evolved from a Common Ancestor on Noah’s Arkt)

The Creation Museum proposed all great apes—excluding humans—find their origin in a single proto-ape representative created by God on the sixth day of creation. Since that supernatural dust-shaping event that ape—through ordinary generation, natural selection, and mutations—has diversified both pre and post-Flood into dozens of living and extinct lineages or organisms we call species. 

For young-earth creationists identifying which types of organisms were part of God’s original creation should be kind of important. It should shape how they interpret anatomical, behavioral, and genetic evidence for common ancestry and how they classify the living things in God’s creation. For example if great apes are the same kind and therefore share a common ancestor then differences in chromosome numbers, ambulatory means, metabolism, social structures and so forth require some explanation for how they could have been derived from that single common ancestor. However, if God made chimpanzees and gorillas as separate kinds they cannot share a common ancestor. Differences between them would need no explanation however, any evidence of common ancestry of chimps and gorillas would need to be explained. In the case of the great apes, the creators of the Creation Museum demonstrate that they accept the evidence for common ancestry of great apes and are striving to provide scientific explanations for the differences. For humans they emphasize the differences from great apes and seek to dismiss the evidence of common ancestry. 

Despite such confident depictions of species origins, defining the meaning of the Hebrew word min translated in English as kind from scriptures has proven to be a difficult task for young earth apologists. They presume that this is the key to identifying what organisms share ancestors in the past and which are created separately during the creation week and thus do not share common ancestry. Today, many young-earth creationists ascribe to an interpretation of creation that holds that kinds are not what we recognize as species today (except possibly human beings). Rather what we identify today as species are simply the end products of processes of diversification of an originally created ancestral kind resulting in the production of many discrete morphologically and/or genetically distinguishable groups of individuals that we call species.

The broad and narrow: creationists seek broad common ancestry while also celebrating the uniqueness of species.  

The move to accept large doses of common ancestry has led to some mixed messaging on the origin of kinds and the specialness of some species. For example, how might the origins pitch look different if the okapi was created separately from the savanna giraffe versus the two sharing a common giraffe-kind ancestor created by God on the sixth day?

I would submit that the answer is foundational to the apologetic message. Take the giraffe kind. Ken Ham and others have spent years telling their audience that the giraffe’s long neck is irreducibly complex. That it can’t have evolved from a shorter necked animal. The implication, sometimes directly said, is that God must have made giraffes the way they are. They are a created kind of animal.  But then some visitors to the Ark Encounter must find it rather jarring when they encounter this sign explaining the origins of giraffes.

If long-necked giraffes were not found in the original creation then the long neck is not irreducibly complex after all since it was derived from a shorter neck. The appeal to a watchmaker designer as the only explanation for highly tuned and complex physiological systems that make long necks possible has far less weight once the definition of a kind is broadened to include the okapi and dozens of extinct short-necked animals as the ancestors of present day long-necked giraffe.  (See Young-Earth Creationism Leads the Short-Necked Okapi to Identify as a Giraffe)

Some creationists now surmise that a shorter-necked ancestor had descendants with increasingly long necks eventually achieving the amazing necks of modern giraffes.  How then are the fine-tuned mechanisms that allow long necks to exist to be explained if not by instantaneous fiat creation?  They must now be explained as the end product of re-scrambled genomic variants and selection of more fit combination by the environment (ie. natural selection) to achieve characteristics not observed in the ancestors (in a very short amount of time, too).  One hypothesis is that God installed the requisite genetic programming (Guliuzza, 2018) in the original short-necked ancestor at its point of creation to make such a transition possible. Nonetheless animals with shorter necks would have to transform incrementally into long-necked descendants via mechanisms generally described as ordinary biological processes rather than direct supernatural creation.

So, it seems, there has been a transition over time by the YEC camp from emphasizing evidence for God creating directly, to God creating through programming (genetics) or guiding (intervention) the development of an organism over time.  

There are innumerable examples of similar incongruous messaging in the creationist’ literature. For example, I’ve written about sea otters that are said to perfectly adapted to sea life because of characteristics made directly by God, and yet the sea otter is said to be a member of a kind of animal of which all other members are adapted to land (Mixed Messages: Confusion over the Origin of Sea Otters at Answers in Genesis)

Unfortunately for creationists, defining kinds and handling the unique characteristics of descendant species doesn’t get any easier when we move our focus away from mammals.  

Let’s look at an example from insects.

A case study of irreducible complexity versus post-creation hyperevolution: the bombardier beetle

Enter the bombardier beetle. Poster child for Intelligent Design and favorite cool bug example of speakers at creation conferences.  Bombardier beetles have a nifty little defense system.  When they are threatened, they can mix chemicals stored in an elaborate set of tubes and reservoirs in their abdomen to create a chemical reaction that results in a jet of boiling hot acid being ejected from their posterior, toward their attacker.  It’s quite a feat of chemical and structural engineering. 

For the creationist there can only be one answer to the origin of the bombardier beetle: God did it! To hear most young-earth apologists speak, the bombardier beetle is so specialized it’s like a mechanical pocket watch, in which each part of the mechanism is absolutely necessary and must be fully formed for the watch to have function.  It seems an obvious question,but how could such an elaborate system have evolved by chance mutations and natural selection?

The creationist literature is replete with such observations.  For example, here are a few quotes from Jerry Bergman on bombardier beetles:   

“The entire structure involving hundreds of parts required to produce, aim and fire its poisonous mixture of unstable chemicals would be totally useless until the entire structure was completed and perfected.”

“Many different species of bombardier beetle exist, all of which are fully functional, and none of which can be used to support a Darwinian scenario. Aside from skunks (which eject a strong-smelling substance at will), no other animal has a structure even remotely similar to the bombardier beetle. If the structure had evolved through small modifications, surely many other animals would exist that likewise have evolved similar, but less (or more) complex structures. Yet, this is not the case: the bombardier beetle, although it is only one of millions of ‘unique’ animals, is completely unique in this one way.” Bergman, Jerry. 2005.  Can evolution produce new organs or structures?  Creation TJ 19(2) 2005.

Similarly,  Melissa Webb at Answers in Genesis last year wrote: “There’s nothing like it in nature, and any sensible person knows that a tiny beetle less than an inch in size could never produce a controlled explosion by accident. It shouts an intelligent Creator.”  (The Mystery of the Exploding Beetle by Melissa Webb on December 22, 2019)

So there you have it. The bombardier beetle is “completely unique” and ‘there’s nothing like it” and “no other animal has a structure even remotely similar to the bombardier beetle.” I agree that “it shouts an intelligent creator” as do all living things but do bombardier beetles necessarily shout out that that creator worked instantaneously to create these beetles without any intermediate processes? 

Furthermore, just how many individuals have this ability and is it true that no other animal has a similar structure? Well, the answer for creationists is partly dependent on how they define the limits of a kind.

The rest of the story:  are bombardier beetles their own kind? 

Note that above, Bergman acknowledges that “many different species of bombardier beetle exist.”  Previously, having heard many young-earth speakers talk about the bombardier beetle, I inferred from them that it was either a single species or (most probably) a group of similar species all having the specialized property of spraying hot benzoquinones as a defensive mechanism.  So it was surprising to learn that the term “bombardier beetle” is given to more than 500 species of beetle found in multiple genera and at least two subfamilies of a larger group, the ground beetles (family Brachinae).  The bombardier beetle actually represents a diverse group of beetle species that may not even be closely related to one another. This was a shocking revelation. 

Looking closer at the young-earth literature, we do find some authors who speak of the diversity of these beetles. For example, Melissa Web’s article provided a helpful graphic in which the bombardier beetles are shown divided into two varieties, the most-studied “exploding” type and those from another group of ground beetles which are sprayers, foamers, and misters (Eisner et al. 2001)of benzoquinones.  Likewise, Mark Armitage (2005) reviewed the ultrastructure of the gland responsible for quinone production in one species and compared it to that of other bombardier beetle species in other genera and acknowledges there is a great variety in the structures of the glands which produce the benzoquinone among bombardier beetles. More on this later. 

Why does it matter that there are over 500 species called bombardier beetles? 

Let’s go back to our original question. What is a kind?  It is very clear from the young-earth literature and public talks that the bombardier beetle is understood to be a uniquely created kind of organism. They claim it couldn’t have evolved from an organism that didn’t also possess the same irreducibly complex characteristics.  So just what is the bombardier beetle kind and what functions / features does it include?

Beetle experts have identified over 500 species of beetles that are given the common name, bombardier beetle.  This name is not a formal taxonomic designation like family, genus or species. Rather it groups all beetles based on a single distinctive character: their particular defensive behavior that includes the ejection of a noxious chemical spray via an exothermic chemical reaction. 

The 500 species are not all placed in the same formal taxonomic group but rather are found in four different subfamilies called tribes (Brachinini, Paussini, Ozaenini, or Metriini) of the ground beetle family Carabidae which contains more than 36,000 species. Could the Carabidae be a created kind? If this is so, the species that possess bombardier capabilities are but a small subset of this group and suggest that this specialized defensive capability evolved from ancestors that didn’t possess this specific defensive system.

So how should we define the bombardier beetle kind?:  1) Coleoptera – all beetles (400,000+ species) are a single created kind, 2) all beetles of the family Carabidae (36,000 species) are a kind, 3) all beetles with the bombardier beetle characteristic are a single kind, or 4) there are multiple beetle kinds that share the bombardier characteristic, but were created separately.  

Creationists usually distinguish kinds based upon some evidence of hybridization among species. Lacking such evidence due to a dearth of hybridization studies (as is in this case with beetles) they would likely group species by morphological similarities. Given that ground beetles share so many characteristics it is understandable that all bombardier beetles are placed within the ground beetle family (Carabidae). The modern creationist inclination is to accept all species grouped at the familial level by taxonomists as a kind. If they followed this practice for insects, they would lump the bombardier beetles into the ground beetle family despite the specialized bombardier abilities of just some of these ground beetles. Hence, the 36,000 species of ground beetles alive today must have derived from a common ancestor God created just 6000 years ago.  

But a greater understanding of the limits of a kind has consequences.  It invokes massive and rapid adaptive evolution within the kind and it strains what has been an effective apologetic tool to creationist speakers: the appeal to irreducible complexity as proof that God created them as they are.  

A ground beetle created kind? This creates more problems than solutions for young earth creationists

If creationists place bombardier beetles in this family, what do they do with the 35,000+ species that don’t have the same irreducible and supposedly utterly unique features that bombardier beetles have?  

Let’s look back at Jerry Bergman’s quote:  “Many different species of bombardier beetle exist, all of which are fully functional, and none of which can be used to support a Darwinian scenario. Aside from skunks (which eject a strong-smelling substance at will), no other animal has a structure even remotely similar to the bombardier beetle. If the structure had evolved through small modifications, surely many other animals would exist that likewise have evolved similar, but less (or more) complex structures. Yet, this is not the case: the bombardier beetle, although it is only one of millions of ‘unique’ animals, is completely unique in this one way.”  Bergman, Jerry. 2005.  Can evolution produce new organs or structures?  Creation TJ 19(2) 2005.

If Bergman is correct then bombardier beetles are unique and had to have been created directly by God. It seems like he would think that other ground beetles must be separately created and thus in a different kind. But much of what he says here is just wrong.  Most importantly, the complex gland responsible for producing, storing and mixing the chemicals that are ejected from bombardier beetles is not unique.

All members of the adephagan suborder of beetles (40,000 species) including the carabids with 36,000 species and water beetles, have paired pygidial glands located in the abdomen, which are used to produce, store, mix and excrete chemicals from the beetles. They can either secrete them by oozing, spraying or crepitation (explosive spraying or misting). Within the carabid beetles there dozens of different forms of acids, ketones, phenols, quinones (the bombardier beetles) that are ejected by these glands for more than just defensive purposes. 

Do young-earth apologists know about members of the ground beetle genus Galerita?  These are called the false bombardier beetles because they have a similar appearance and also spray chemicals at their attacker. However, that spray is formic acid (the same substance that ants make) rather than benzoquinones (Rossini 1997). Are these also irreducibly complex and thus a unique creation and their own kind as well? 

So all carabid beetles have this chemical production capacity gland but they deploy somewhat different chemicals and for different purposes. Bergman and other creationists imply—possibly due to ignorance—that the apparatus in bombardier beetles is unique when it is not. Oddly, Armitage and Mullisen (2003) mention Galerita in their paper about pygidial glands of Bombardier beetles but only mention that Galerita beetles are inhibited by the bombardier beetle spray not that these false bombardier beetles can spray them back with a different chemical. Yes, the particular chemical concoction they produce in this apparatus is different from (and more explosive than) other ground beetles,  but the essential components for such a system are all present in Galerita and thousands of ground beetles of this family. 

Another specialization among ground beetles as amazing as the bombardier defense 

I saved the biggest and most interesting revelation for the end. For creationists that insist that bombardier beetles are specially designed, their own logic should lead them to realize that bombardier beetles cannot be a single created kind. There must be at least two created kinds of bombardier beetles, albeit with similar defensive mechanisms.

How can I say this? Looking at the differences between bombardier beetles (figure below), it becomes apparent that beetles in the subfamilies Brachinini and Paussini (and possibly others) cannot be the same kind.  Young-earthers who insist that a kind is defined by the presence of supposedly irreducibly complex characteristics run into a problem, because the Paussini ground beetles are themselves highly specialized with a completely different set of unique characteristics. This is because Paussini ground beetles are also ant nest beetles.

Ant nest beetles make their home in ant nests (myrmecophiles). Yes, hundreds of Paussini bombardier beetle species live in ant nests where they are parasites on their hosts. How do they live with the ants without the ants attacking them? They excrete chemicals that identify themselves as ants. In addition, they have anatomical structure that emits sounds (Di Giulio et al, 2014, Giulio et al. 2015) that mimic ant queens causing the ants to treat them with great care. I have no doubt that if a creationist read about this, they would marvel at the amazing complexity of the auditory devices and their ability to manipulate the behavior of the ants and shout: God did it! They would consider the chemical cues and sound-making capacity as irreducibly complex characteristics that could not have originated via any natural process.   

The Paussini bombardier beetles have so many unique characteristics of their own. Applying the logic found in popular creationist’ literature, we would expect them to conclude that these beetles are a separate creation—their own kind. 

A narrow view of kinds focused on unique differences or a broad view of kinds focused on shared similarities? 

The conundrum for the young-earth taxonomists is apparent. The ecology of living with ants as if they were ants sets the Paussini beetle apart from other beetles.  At the same time, they also share so many features with other ground beetles that it is tempting to consider all ground beetles as a single kind.

 To this point, young-earth popularizers lump the bombardier beetles together in a single kind.  What I am suggesting is that unless they wish to go further and place them into a broader kind including all ground beetles they should realize that they may need to split the bombardier beetles into multiple created kinds. Yes, the Paussini and Brachinini bombardier beetles all excrete the same benzoquinone hot chemicals. But digging a little deeper in the literature reveals that, although they produce the same benzoquinone chemical, how they make that chemical and how they eject it from their bodies (some spray and some foam) represents some significant differences (Armitage and Mullisen, 2003; Di Guilio et al. 2015, Eisner et al. 2001; Muzzi et al, 2019a, 2019b, and Rork et al 2019) Further, the auditory and other ant-manipulation characteristics of the ant-nest beetles suggest that they deserve to be considered their own created kind.

So, what is a kind of beetle?  You may be confused, and I am too. One thing is clear, the boundaries of a kind depend upon what characteristic you  focus. The Creation Museum has elected to focus on the similarities of great apes versus their differences, will they likewise ignore the unique characteristics of bombardier beetles and embrace the similarities of all ground beetles or maybe even all beetles? 

Post-creation rapid evolution of ground beetles?

The very fact that even a few dozen of the 500+ species of bombardier beetles possess significant anatomical differences suggests that if they truly are all one “kind” of organism then dramatic changes have occurred to the defensive systems of these beetles. The implications of this fact are that they must be far more malleable by evolutionary mechanisms than are generally recognized by young-earth and intelligent design advocates. Imagine if they were to examine a dozen other parts of the beetle anatomy such as the stribulatory—a sound-emitting—organ of the ant nest beetles? What might they conclude about the intrabaraminic (within a kind) diversity is possible? And, if this kind of diversity is, in fact, possible, what does this say about the concept of irreducible complexity?

What about taking that broader understanding of an insect kind—the direction that young-earthers have been moving in recent decades?  If they are consistent with the family designation as the most likely boundary of a kind, then they are going to need to lump all ground beetles (family Carabidae) together as a single type of created life. In this scenario all ground beetles are related by ancestry to one another. If this is true, the specializations such as making benzoquinones or chemicals that mimic ant pheromones or the ability to make sounds that appeal to ants are uniquely derived traits within that ground beetle kind. Rather than being irreducibly complex, they would have to be viewed as being the products of rapid evolution of the originally created beetle kind.  This rapid speciation results in a diversity of ground beetles, some of which we are awed by their incredible uniqueness. 

As we have seen in this brief review, there is much more diversity of structure, function, and behavioral traits in and among these beetles than young-earth apologists either know about or recognize. They must decide if the uniqueness of bombardier beetles warrants their claim of having a special place as a unique creation or if they should come to understand the bombardier capacity as one of many evolved traits within a kind. 

The short summary

1. Bombardier beetles have been a favorite example of possessing a complex trait that could not have evolved and therefore must have been created by God, fully formed, rather than having evolved from non-bombardier ancestors
2. There are hundreds of beetles with bombardier abilities however they don’t all perform the action in the same way suggesting at least some diversification (evolution) of their internal structures and behaviors since their creation. 
3. Bombardier beetles aren’t all closely related to each other. Rather some bombardier beetles–such as the ant nest beetles–are more closely related to non-bombardier beetles in other subfamilies than they are to other bombardier beetles (i.e. they are a paraphyletic group.) This is why they are placed in disparate subfamilies of a much larger one, the ground beetle family. This observation that there are at least two separate lineages of bombardier beetles is devastating to their claim of irreducible complexity and this issue hasn’t been addressed by the young-earth literature.
4. All ground beetles have the same organ system referred to in this post—the pygidial gland—that bombardier beetles have. They don’t all make benzoquinones but are capable of making a range of other caustic compounds used for multiple purposes including defense.
5. The presence of internal structures capable of producing and secreting chemicals  from the abdomen is not special to bombardier beetles and appears to be a general property suited for adaptation into more specialized versions from a more general ancestor.
6. If all ground beetles are of the same kind, one is at a loss to explain how functions such as benzoquinone foams and queen ant mimicry, thought previously by creationists to clearly be irreducibly complex, went on instead to evolve from common ancestors in just a few thousand years.

Conclusion: The broad definition of kind that is popular among creationist today contradicts 40 years of messages conveyed about bombardier beetles as unique creations that defy any evolutionary explanation. The push to explain species’ diversity as the product of rapid diversification/evolution from a created ancestral kind over just a few thousand years undermines young-earth apologists who point to specialized characteristics (the irreducible complexity claim) of individual species as incapable of having formed by known evolutionary processes. 

Next up.. 

I want to explore the young-earth understanding of kinds of insects further by looking at other insect groups such as dragonflies, cockroaches and termites. 

Update:  Below is a video I made about YEC and walking stick insect origins.  I called this “Kind of Confusing Part II” because it follows up on this post about bombardier beetles. 

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PS The young-earth literature has some catch up work to do. There have been many important studies published on bombardier beetles in the last decade that haven’t been, as yet, accounted for.. Most young-earth articles simply repeat the same story they have for 30 years and seem to be unaware–as I was until I looked–that the bombardier story is far more complex than the simple irreducible complexity they are fond of recounting.  

Mark Armitage in 2003 suggested he would engage in future work to elucidate the variation among these beetles but so far none of that work has been published that I am aware of.  There is an initiative at Liberty University to use bombardier beetles in biomimicry research but again, nothing new seems to have come from that yet. I have yet to find a serious discussion in the young-earth literature about the meaning of variation within the bombardier beetles or how these beetles may relate to other ground beetles. They seem content to not peek behind the curtain and find out more about a favorite example of design lest they discover things that make the story more messy.   

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Literature cited and used in preparation for writing this article:

Armitage, M.H. and Mullisen, L., 2003.  Preliminary observations of the pygidial gland of the Bombardier Beetle, Brachinus sp., Journal of Creation 17(1):95–102.

Attygalle, Athula B., Sihang Xu, Wendy Moore, Reilly McManus, Aman Gill, and Kipling Will. “Biosynthetic origin of benzoquinones in the explosive discharge of the bombardier beetle Brachinus elongatulus.” The Science of Nature 107, no. 4 (2020): 1-11.\

Carcamo-Noriega, Edson Norberto, Shyam Sathyamoorthi, Shibdas Banerjee, Elumalai Gnanamani, Monserrat Mendoza-Trujillo, Dulce Mata-Espinosa, Rogelio Hernández-Pando, José Ignacio Veytia-Bucheli, Lourival D. Possani, and Richard N. Zare. “1, 4-Benzoquinone antimicrobial agents against Staphylococcus aureus and Mycobacterium tuberculosis derived from scorpion venom.” Proceedings of the National Academy of Sciences 116, no. 26 (2019): 12642-12647.

Di Giulio, Andrea, Simone Fattorini, Wendy Moore, James Robertson, and Emanuela Maurizi. “Form, function and evolutionary significance of stridulatory organs in ant nest beetles (Coleoptera: Carabidae: Paussini).” European Journal of Entomology 111, no. 5 (2014): 692.

Di Giulio, Andrea, Emanuela Maurizi, Francesca Barbero, Marco Sala, Simone Fattorini, Emilio Balletto, and Simona Bonelli. “The pied piper: a parasitic beetle’s melodies modulate ant behaviours.” PLoS One 10, no. 7 (2015): e0130541. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0130541

Di Giulio, Andrea, Maurizio Muzzi, and Roberto Romani. “Functional anatomy of the explosive defensive system of bombardier beetles (Coleoptera, Carabidae, Brachininae).” Arthropod Structure & Development 44, no. 5 (2015): 468-490. https://www.sciencedirect.com/science/article/abs/pii/S1467803915000766

Eisner, Thomas, Daniel J. Aneshansley, Jayne Yack, Athula B. Attygalle, and Maria Eisner. “Spray mechanism of crepidogastrine bombardier beetles (Carabidae; Crepidogastrini).” Chemoecology 11, no. 4 (2001): 209-219.

Giglio, Anita, Pietro Brandmayr, Federica Talarico, and Tullia Zetto Brandmayr. “Current knowledge on exocrine glands in carabid beetles: structure, function and chemical compounds.” ZooKeys 100 (2011): 193.

Randy J. Guliuzza, P.E., M.D. 2018. Engineered Adaptability: Designed Mechanisms Best Explain Convergent Traits. Acts & Facts. 47 (5).

Housecroft, Catherine E. “Nature’s Chemical Weapons: Beetle Defenses.” CHIMIA International Journal for Chemistry 73, no. 5 (2019): 420-421.

Moore, Wendy. “Phylogeny of the western Hemisphere Ozaenini (Coleoptera: Carabidae: Paussinae) based on DNA sequence data.” Annals of Carnegie Museum 77, no. 1 (2008): 79-92.

Muzzi, Maurizio, Wendy Moore, and Andrea Di Giulio. “Morpho-functional analysis of the explosive defensive system of basal bombardier beetles (Carabidae: Paussinae: Metriini).” Micron 119 (2019): 24-38.

Muzzi, Maurizio, and Andrea Di Giulio. “The ant nest “bomber”: Explosive defensive system of the flanged bombardier beetle Paussus favieri (Coleoptera, Carabidae).” Arthropod structure & development 50 (2019): 24-42.

Ober, Karen A. “Phylogenetic relationships of the carabid subfamily Harpalinae (Coleoptera) based on molecular sequence data.” Molecular Phylogenetics and Evolution 24, no. 2 (2002): 228-248.

Rork, Adam M., István Mikó, and Tanya Renner. “Pygidial glands of Harpalus pensylvanicus (Coleoptera: Carabidae) contain resilin-rich structures.” Arthropod structure & development 49 (2019): 19-25.

Rossini, Carmen, Athula B. Attygalle, ANDREs GONZAlez, Scott R. Smedley, Maria Eisner, Jerrold Meinwald, and Thomas Eisner. “Defensive production of formic acid (80%) by a carabid beetle (Galerita lecontei).” Proceedings of the National Academy of Sciences 94, no. 13 (1997): 6792-6797.

Will KW, Attygalle A & Herath K. 2000. New defensive chemical data for ground beetles (Coleoptera: Carabidae): interpretations in a phylogenetic framework. Biological Journal of the Linnean   Society 71, 459-481.

Will KW, Gill AS, Lee H, Attygalle AB. 2010. Quantification and evidence for mechanically metered release of pygidial secretions in formic acid-producing carabid beetles. Journal of Insect  Science 10, available online: insectsicence.org/10.12.

Cover image:  Bombardier Beetle – Paussinae subfamily, Gorongosa National Park, Mozambique. Photo: Judy Gallager (CC By 2.0)
Editing provided by Michael Callen