"gigantopterid" = an English noun describing large leaves with complex reticulate venation resembling the Cathaysian fossil seed plant genus Gigantopteris and North American genus Delnortea of the Permian Period, 260 million years ago"

You are here: Entomology and Tool Kit Links


[ Links to Web Pages on Insect Biology, Developmental Tool Kits, and Paleoentomology ]

Coleopterists Society:
The Coleopterists Society is devoted to the study of beetles ...

Entomological Society of America (ESA):
This is the official home page of the Entomological Society of America ... LINK

International Palaeoentomological Society (IPS):
Follow this link to the official web site for this professional scientific organization. This is a gateway to the literature on fossil insects. Image galleries are included on this web site ...

Mississippi Entomological Museum:
Professor Richard Brown and team have created this great web site on entomology ...

Palaeontological Institute Laboratory of Arthropods, Russian Academy of Sciences:
This is a web site devoted to palaeoentomology in Russia ...

Professor Roy Beckenmeyer's Web Site:
This site contains many useful links to other web sites on fossil insects. In addition Professor Beckenmeyer provides the viewer with images of insect fossils ... LINK

Professor Tom Bürglin's Homeobox Page:
This is a useful primer on the role of homeobox genes and transcription factors in animal development ... LINK

Professor Sean Carroll's Web Site:
This link leads to the personal web site of Sean B. Carroll, Ph.D. ...

Professor Bryan Danforth's Web Site:
The Danforth Lab web site, which is sponsored by the Cornell University Department of Entomology, contains this overview of bees and the evolution of flowers, among other topics of entomological interest ...

Professor Diana Percy's Psillid Web Site:
Devoted to the biology and fossil history of leaf-mining Hemiptera - a great place to start leaf hopping ... LINK

University of California Essig Museum of Entomology:
The web site of UC Berkeley's Essig Museum includes multiple links to other web sites devoted to entomology ... LINK

University of Washington Fold-it Web Site:
This web site is sponsored by the University of Washington Department of Computer Science & Engineering Department, complete with puzzles useful for teaching biochemistry and developmental regulation by proteins ...

The background image is a scanning electron micrograph of the head of Haptoncus tahktajanii (Nitidulidae, Coleoptera), photographed by Al Soeldner, Oregon State University Electron Microscopy Laboratory. Haptoncus tahktajanii is a phytophagous associate of the island endemic tree Degeneria vitiensis (Degeneriaceae, Magnoliales, Magnolianae). Field work on Degeneriaceae of the Fiji Islands was sponsored by a grant from the National Geographic Society.

Primer on Developmental Tool Kits:

Some of the links to the other web sites listed above lead to educational material having to do with the developmental tool kit. The eukaryotic tool kit is the biochemical machinery necessary to orchestrate the development of living bodies, which involves interacting genes, hormones, and transcription factors (TFs), among other molecules of cells, tissues, and organs. Engraled and Leafy, are two structurally similar homeodomain (DNA-binding) TFs.

The right-hand image is reproduced from Figure 6 on page 2634 of Hamès et al. (2008), "Comparison of LFY-C with paired and homeodomain DNA binding. (A) Two orthogonal views of LFY-C helices α1 - α3 bound to their DNA target site [red] superimposed with the three helical bundle core of the N-terminal subdomain of the paired domain of Drosophila Prd [blue, PDB-id: 1pdn]. (B) Superposition with the homeodomain of Drosophila engrailed bound to DNA [yellow, PBD-id: 1hdd], where the centre of recognition helix α3 inserts into the major groove."

Reprinted by permission from Macmillan Publishers Ltd: The European Molecular Biology Organization (EMBO) Journal, Hamès, C., D. Ptchelkine, C. Grimm, E. Thevenon, E. Moyroud, F. Gérard, J.-L. Martiel, R. Benlloch, F. Parcy, and C. W. Müller. 2008. Structural basis for LEAFY floral switch function and similarity with helix-turn-helix proteins, The EMBO Journal 27: 2628-2637, copyright ©2008.

Does the developmental tool kit have anything to do with seed plant phylogenetics, the origin of flowering plants, and coevolution with some holometabolous insects? Yes, though some paleontologists have yet to embrace the concept. In fact, molecular coevolution of insect and seed plant developmental tool kits, cis-regulatory modules (CRMs), and gene-regulatory networks (GRNs), might explain diversification in Paleozoic seed plant lineages, origin of flowers, and the origin of angiosperms and coevolution with the Holometabola.

"By considering entire GRNs involved in key developmental processes and investigating changes in entire GRNs across evolutionary lineages researchers can begin to piece together the fundamental genetic and genomic principles underlying the conservation and evolution of form."

The previous statement is quoted from the concluding section eight on page 87 of C. D. Specht and D. G. Howarth, (2015), Adaptation in flower form: a comparative evodevo approach, New Phytologist 206: 74-80.

A growing body of morphological evidence suggests that cones and flowers are reproductive short shoots (Christianson and Jernstedt 2009). Fertile spur shoots are demonstrably ancient organs known from Permo-carboniferous seed plant fossils. Further, molecular phylogenetic studies of homeodomain proteins and TFs posit deep conservation of cone and floral CRMs, GRNs, efflux carriers, and auxin-based polarity networks (PINs).

"Our data suggest that the interactions governing flower development in core eudicots were already established at the base of extant angiosperms and remained highly conserved since then. Specifically, our results indicate that the heterodimerization between DEF-like and GLO-like proteins was already present in the [most common recent ancestor] MRCA of extant angiosperms and was virtually never rewired" (page 1438, Discussion, Conservation of the MADS-domain protein interaction pattern during angiosperm evolution, Melzer et al. 2014).

Leafy protein regulates gibberellin (GA)-mediated transition to flowering and downstream expression of MIKC-type MADS-box genes that determine floral organ identity (H. Yu et al. 2004, Theißen and Melzer 2007, Hou et al. 2008, Glover 2014, Glover et al. 2015).

"The acquisition R390 [of LEAFY protein] might therefore have been important for flower evolution."

The previous statement is quoted from page 2635 of C. Hamès, D. Ptchelkine, C. Grimm, E. Thevenon, E. Moyroud, F. Gérard, J.-L. Martiel, R. Benlloch, F. Parcy, and C. W. Müller (2008), Structural basis for LEAFY floral switch function and similarity with helix-turn-helix proteins. The EMBO Journal 27: 2628-2637. The phrase in brackets [] is mine.

"Our study reveals that the LFY master regulator, which determines flower meristem fate and controls the expression of floral organ identity genes, shares structural similarity with other HTH proteins, indicating that this universal DNA-binding motif has also been adopted in plants to trigger major developmental switches" (page 2635, Hamès et al. 2008).

Engraled (en), also spelled "engrailed" in the literature, is an insect compartment selector gene that encodes the Engraled homeodomain TF that determines the posterior identity of embryos and wings of the Drosophila model arthropod. The Apterous (ap) compartment selector gene encodes Apterous protein, which is another TF involved in subdivision of imaginal discs into dorsal and ventral compartments of developing fruit flies (S. B. Carroll et al. 2005).

The structure of the LEAFY [LFY]-C developmental tool kit protein of Arabidopsis thaliana shown in the image above, consists of a HTH DNA-binding motif with uncanny similarities to the active motif of Drosophila Engraled homeodomain protein, Tc3A transposase, and Hin recombinase enzymes (Hamès et al. 2008).

Dimeric LEAFY protein and auxin form modules, which together with PINs help determine floral primordia in shoot apical meristems (SAMs) of some model angiosperms.

"Its emergence [of a reproductive regulatory network] probably involved changes in cis-elements of recruited targets, to place them under LFY control, as well as the establishment of novel protein-protein interactions." (page 351, Moyroud et al. 2010).

Finally, in a 2016 Annals of Botany (Oxford) Special Issue, Theißen and Melzer introduce the concept of "developmental robustness" to understand evolution of morphological complexity including "new organs or structures," examples being certain clades of insects and eudicot flowering plants.

"... herein lies a challenge for the next generation of biologists: if the mechanisms behind the formation of diverse organs are ancient and highly conserved, then parallel evolution must be considered ..." (quoted from page 822, Deep homology and parallel evolution, Shubin et al. 2009).

From an evo-devo research perspective, namely CRMs, TFs, GRNs, and PINs and underlying biochemical mechanisms (e.g. homeodomain proteins, hormones, and regulatory networks) sensu Becker, Carroll, Meyerowitz, and Shubin, among others, is the angiosperm flower with its nested structures and reproductive modules, a deeply-conserved seed plant organ? Absolutely.

Background Reading:

Alvarez, J. M., J. Sohlberg, P. Engström, Tianqing Zhu, M. Englund, P. N. Moschou, and S. von Arnold. 2015. The WUSCHEL-RELATED HOMEOBOX 3 gene PaWOX3 regulates lateral organ formation in Norway spruce. New Phytologist 208(4): 10781088.

Baum, D. A. and L. C. Hileman. 2006. A developmental genetic model for the origin of the flower. Pp. 3-27 In: C. Ainsworth (ed.), Volume 20, Annual Plant Reviews, Flowering and Its Manipulation. Sheffield: Blackwell Publishing Ltd., 304 pp.

Becker, A. 2016. Tinkering with transcription factor networks for developmental robustness in Ranunculales flowers. Annals of Botany 117: 845-858.

Carroll, S. B. 2008. Evo-devo and an expanding evolutionary synthesis: a genetic theory of morphological evolution. Cell 134(1): 25-36.

Carroll, S. B., J. K. Grenier, and S. D. Weatherbee. 2005. From DNA to Diversity: Molecular Genetics and the Evolution of Animal Design. Malden: Blackwell Publishing, 258 pp.

Christianson, M. L. and J. A. Jernstedt. 2009. Reproductive short-shoots of Ginkgo biloba: a quantitative analysis of the disposition of axillary structures. American Journal of Botany 96(11): 1957-1966.

Costanzo, E., C. Trehin, and M. Vandenbussche. 2014. The role of WOX genes in flower development. Annals of Botany (Oxford) 114 (7): 1545-1553.

Floyd, S. K., J. G. Ryan, S. J. Conway, E. Brenner, K. P. Burris, J. N. Burris, T. Chen, P. P. Edger, Sean W. Graham, J. H. Leebens-Mack, J. Chris Pires, C. J. Rothfels, E. M. Sigel, D. Wm. Stevenson, C. N. Stewart, Jr., G. K-S. Wong, and J. L. Bowman. 2014. Origin of a novel regulatory module by duplication and degeneration of an ancient plant transcription factor. Molecular Phylogenetics and Evolution 81: 159173.

Glover, B. 2014. Understanding Flowers and Flowering, Second Edition. Oxford: Oxford University Press, 320 pp.

Glover, B. J., C. A. Airoldi, S. F. Brockington, M. Fernández-Mazuecos, C. Martínez-Pérez, G. Mellers, E. Moyroud, and L. Taylor. 2015. How have advances in comparative floral development influenced our understanding of floral evolution? International Journal of Plant Sciences 176(4): 307-323.

Gramzow, L., L. Weilandt, and G. Theißen. 2014. MADS goes genomic in conifers: towards determining the ancestral set of MADS-box genes in seed plants. Annals of Botany (Oxford) 114(7): 1407-1429.

Hamès, C., D. Ptchelkine, C. Grimm, E. Thévenon, E. Moyroud, F. Gérard, J.-L. Martiel, R. Benlloch, F. Parcy, and C. W. Müller. 2008. Structural basis for LEAFY floral switch function and similarity with helix-turn-helix proteins. The EMBO Journal 27: 2628-2637.

Hou, X., W.-W. Hu, L. Shen, L. Y. C. Lee, Z. Tao, J.-H. Han, and H. Yu. 2008. Global identification of DELLA target genes during Arabidopsis flower development. Plant Physiology 147: 1126-1142.

Melzer, R., A. Härter, F. Rümpler, S. Kim, P. S. Soltis, D. E. Soltis, and G. Theißen. 2014. DEF- and GLO-like proteins may have lost most of their interaction partners during angiosperm evolution. Annals of Botany (Oxford) 114 (7): 1431-1443.

Melzer, R., Y.-Q. Wang, and G. Theißen. 2010. The naked and the dead: the ABCs of gymnosperm reproduction and the origin of the angiosperm flower. Seminars in Cell & Developmental Biology 21(1): 118-128.

Meyerowitz, E. M. 2002. Plants compared to animals: the broadest comparative study of development. Science 295: 1482-1485.

Moyroud, E., E. Kusters, M. Monniaux, R. Koes, and F. Parcy. 2010. LEAFY blossoms. Trends in Plant Science 15: 346-352.

Nardmann, J., P. Reisewitz, and W. Werr. 2009. Discrete shoot and root stem cell-promoting WUS/WOX5 functions are an evolutionary innovation of angiosperms. Molecular Biology and Evolution 26(8): 1745-1755.

Nardmann, J. and W. Werr. 2013. Symplesiomorphies in the WUSCHEL clade suggest that the last common ancestor of seed plants contained at least four independent stem cell niches. New Phytologist 199(4): 1081-1092.

Niklas, K. J. and U. Kutschera. 2009. The evolutionary development of plant body plans. Functional Plant Biology 36: 682-695.

Rothwell, G. W., S. E. Wyatt, and A. M. F. Tomescu. 2014. Plant evolution at the interface of paleontology and developmental biology: an organism-centered paradigm. American Journal of Botany 101(6): 899-913.

Sanders, H., G. W. Rothwell, and S. E. Wyatt. 2007. Paleontological context for the developmental mechanisms of evolution. International Journal of Plant Sciences 168: 719-728.

Sayou, C., M. Monniaux, M. H. Nanao, E. Moyroud, S. F. Brockington, E. Thévenon, H. Chahtane, N. Warthmann, M. Melkonian, Y. Zhang, G. K.-S. Wong, D. Weigel, F. Parcy, and R. Dumas. 2014. A promiscuous intermediate underlies the evolution of LEAFY DNA binding specificity. Science 343(6171): 645-648.

Shubin, N. and C. R. Marshall. 2000. Fossils, genes, and the origins of novelty. Paleobiology 26: 324-340.

Shubin, N., C. Tabin, and S. Carroll. 2009. Deep homology and the origins of evolutionary novelty. Nature 457: 818-823.

Soltis, P. S. and D. E. Soltis. 2014. Chapter 4. Flower diversity and angiosperm diversification. Pp. 85-102 In: J. L. Riechmann and F. Wellmer (eds.), Flower Development: Methods and Protocols. New York: Springer, 475 pp.

Specht, C. D. and M. E. Bartlett. 2009. Flower evolution: the origin and subsequent diversification of the angiosperm flower. Annual Review of Ecology, Evolution, and Systematics 40: 217-243.

Specht, C. D. and D. G. Howarth. 2015. Adaptation in flower form: a comparative evodevo approach. New Phytologist 206: 74-80.

Theißen, G. 2009. Saltational evolution: hopeful monsters are here to stay. Theory in Biosciences 128: 43-51.

Theißen, G. and R. Melzer. 2007. Molecular mechanisms underlying origin and diversification of the angiosperm flower. Annals of Botany 100(3): 1-17.

Theißen, G. and R. Melzer. 2016. Robust views on plasticity and diversity. Annals of Botany 117: 693-697.

Tomescu, A. M. F. 2016. Development: paleobotany at the high table of evo-devo. Current Biology 26: R505-508.

Vialette-Guiraud, A. C. M., A. Andres-Robin, P. Chambrier, R. Tavares, and C. P. Scutt. 2016. The analysis of gene regulatory networks in plant evo-devo. Journal of Experimental Botany 67(9): 2549-2563.

Yu, H., T. Ito, Y. Zhao, J. Peng, P. Kumar, and E. M. Meyerowitz. 2004. Floral homeotic genes are targets of gibberellin signaling in flower development. Proceedings of the National Academy of Sciences 101(20): 7827-7832.

Computer-assisted Exercise in the Paleobiology of Insect Vision and the Floral Tool Kit:

According to Grimaldi and Engel (page 469, Figure 12.1, 2005) Panorpida, which are a sister group to the Hymenoptera (ants, bees, and wasps), diverged more than 290 MYA, roughly coincident with the angiosperm-gymnosperm split. There are estimates published in the literature that crown group flowering plants originated 221 MYA in the Middle Triassic (Foster et al. 2017).

Further, several published papers appearing in the last 25 years help us to understand the paleobiology of pollination by insects from several disparate lines of thought (Chittka et al. 1994, Chittka 1996, Labandeira 1998, Dong Ren 1998, Labandeira 2000, Chittka et al. 2001, Dong Ren et al. 2009).

The scanning electron micrograph shown on the right-hand side of the page is the anterior front part of the head of Haptoncus tahktajanii (Nitidulidae, Coleoptera), the cucujiform phytophagous associate of the primitive magnoliid flowering plant Degeneria vitiensis (Degeneriaceae, Magnoliales, Magnoliidae). Many gustatory, olfactory, and visual sensory organs of the nitidulid beetle are visible in the image including antennae, sensillae, compound eyes, mandibles, maxillae, and labia, × 100.

Some of the floral organs of Degeneria vitiensis are covered with bright-yellow, oily exudate and emit volatile hydrocarbons (VOCs) including fragrant terpenes and acetate esters. What if any, of the nitidulid head capsule appendages pictured above, function as visual sensory receptors of UV-absorbing natural plant products? As a classroom or seminar exercise, design field experiments to answer this question, among others.

Nitidulids were collected by the author from flowers clipped from the canopy of Degeneria trees at the Mount Naitaradamu Study Area, Viti Levu, Fiji Islands in 1986. The National Geographic Society is acknowledged for providing research funding for this work. The photograph is by Al Soeldner of the Oregon State University Electron Microscope Laboratory.

After completing the problem on paleobotany and taphonomy, which is described on another page of this web site, design experiments using artificial 3-D printed constructs of whole plant organs to shed light on the paleobiology of arthropod and seed plant interactions.

Work by Chittka (1996), Briscoe and Chittka (2001), and Chittka et al. (2001) are key toward understanding the paleobiology of panorpoids. Implications of these three studies toward an understanding of the deep time evolution of pollination mutualisms and color and scent perception by species of the "Big Five" holometabolous insect orders and late Paleozoic seed plants, when taking into account the paleobiology of the arthropod brain, are absolutely profound.

"It is likely that trichromacy existed prior to the advent of angiosperm flowers" (page 138, Chittka 1996).

Apply three-dimensional (3-D) printing technology to create artificial, dimorphic foliar or floral organs of a hypothetical Permo-carboniferous protoflower (reproductive short- [spur-] shoot) as a class science project. Carry-out experiments to prove or disprove ideas proposed by Briscoe, Chittka, Labandeira, and Dong Ren, among others.

Perform a Google Scholar literature search to retrieve publications guiding the design of experiments on insect sensory perception of the 3-D printed artificial constructs of reproductive short- (spur-) shoots to be doped with food rewards, scent, tactile cues, and/or ultraviolet-absorbing natural products. There are at least two examples in the library.

Anchor studies from the Chittka and Strausfeld labs (Chittka et al. 1994, Chittka 1996, Strausfeld et al. 1998, Briscoe and Chittka 2001, Chittka et al. 2001, Strausfeld 2009, Xiaoya Ma et al. 2012, Edgecombe et al. 2015, Xiaoya Ma et al. 2015) may provide clues.

When supported by paleobotanical evidence, were anthocyanic fertile short (spur) shoots of Permo-carboniferous seed plants visually discernable to pollinivores, paleodictyopterans, and predatory wasps in "sensory color space" (page 846, The use of floral morphospaces in evolutionary ecology: the sensory color space, Chartier et al. 2014)?

"Hence, a flower that stands out against green foliage can be predicted to be equally conspicuous against brown soil, grey stones and other inorganic backgrounds" (page 1505, Chittka et al. 1994).

Did protohymenopterans including sawflies (xyelids) possess mushroom bodies, optic lobes, and sensory tool kits necessary to visualize pigments of foliar organs, including protoflowers?

After reading the evo-devo primer presented in the previous section, were tool kit interactions between auxin, homeodomain protein TFs (CUC2, Class III HD-Zip, KNOTTED/ARP, WUSCHEL), and PIN proteins, present in foliar organs and reproductive short- (spur-) shoots of Paleozoic seed plants?

Does the foliar morphology and leaf-midrib anatomy of Permian delnorteas and evolsonias display the developmental fingerprint of a magnoliid or eudicot molecular tool kit?

If the Triassic seed plant Sanmiguelia lewisii displays a monocot tool kit fingerprint how does the review by Chanderbali et al. (2016) help us understand the evo-devo of flowers?

Based on the phenotypes of developmental regulation visible in detached and shed Permian seed plant leaf fossils, was the foliar tool kit of delnorteas, evolsonias, and retuse taeniopteroids underpinned by the same WOX homeobox genes, WUSCHEL homeodomain proteins, and CUC2 TFs as extant model flowering plant species?

How could a team of paleobiologists prove these ideas?

Can you apply techniques of phylogenetics to a paleobiological data set to zoom-in on this problem?

Answering some of the questions posed above might help us to better understand the paleobiology of flowers and arthropod vision. Mining and describing fossilized cones and protoflowers and documenting evidence of developmental fingerprints seen in detached and shed foliar and floral organs, might help paleobiologists calibrate seed plant molecular tool kit phylogenies.

Background Reading:

Alvarez, J. M., J. Sohlberg, P. Engström, Tianqing Zhu, M. Englund, P. N. Moschou, and S. von Arnold. 2015. The WUSCHEL-RELATED HOMEOBOX 3 gene PaWOX3 regulates lateral organ formation in Norway spruce. New Phytologist 208(4): 10781088.

Briscoe, A. D. and L. Chittka. 2001. The evolution of color vision in insects. Annual Review of Entomology 46: 471510.

Chanderbali, A. S., B. A. Berger, D. A. Howarth, P. S. Soltis, and D. E. Soltis. 2016. Evolving ideas on the origin and evolution of flowers: new perspectives in the genomic era. Genetics 202: 1255-1265.

Chartier, M., F. Jabbour, S. Gerber, P. Mitteroecker, H. Sauquet, M. von Balthazar, Y. Staedler, P. R. Crane, and J. Schönenberger. 2014. The floral morphospace - a modern comparative approach to study angiosperm evolution. New Phytologist 204: 841-853.

Chittka, L. 1996. Does bee color vision predate the evolution of flower color? Naturwissenschaften 83: 136-138.

Chittka, L., A. Schmidt, N. Troje, and R. Menzel. 1994. Ultraviolet as a component of flower reflections, and the colour perception of Hymenoptera. Vision Research 34: 1489-1508.

Chittka, L., J. Spaethe, A. Schmidt, and A. Hickelsberger. 2001. 6. Adaptation, constraint, and chance in the evolution of flower color and pollinator color vision. Pp. 106-126 In: L. Chittka and J. D. Thomson (eds.), Cognitive Ecology of Pollination, Animal Behaviour and Floral Evolution. Cambridge: Cambridge University Press, 344 pp.

Edgecombe, G. D., Xiaoya Ma, and N. J. Strausfeld. 2015. Unlocking the early fossil record of the arthropod central nervous system. Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 370(1684): DOI 10.1098/rstb.2015.0038.

Foster, C. S. P., H. Sauquet, M. van der Merwe, H. McPherson, M. Rossetto, and S. Y. W. Ho. 2017. Phylogenomic timescale for angiosperm evolution: evaluating the impact of genomic data and priors on Bayesian estimates of the angiosperm evolutionary timescale. Systematic Biology XX: XXX-XXX.

Grimaldi, D. and M. S. Engel. 2005. Evolution of the Insects. Cambridge: Cambridge University Press, 755 pp.

Labandeira, C. C. 1998. How old is the flower and the fly? Science 280: 57-59.

Labandeira, C. C. 2000. The paleobiology of pollination and its precursors. Pp. 233-269 In: R. A. Gastaldo and W. A. DiMichele (eds.), Phanerozoic Terrestrial Ecosystems. Paleontological Society Papers 6: 233-269.

Ma, Xiaoya, G. D. Edgecombe, Xianguang Hou, T. Goral, and N. J. Strausfeld. 2015. Preservational pathways of corresponding brains of a Cambrian euarthropod. Current Biology 25(22): 2969-2975.

Ma, Xiaoya, X. Hou, G. D. Edgecombe, and N. J. Strausfeld. 2012. Complex brain and optic lobes in an early Cambrian arthropod. Nature 490(7419): 258-262.

Ren, Dong. 1998. Flower-associated Brachycera flies as fossil evidence for Jurassic angiosperm origins. Science 280: 85-88.

Ren, Dong, C. C. Labandeira, J. A. Santiago-Blay, A. Rasnitsyn, C-K. Shih, A. Bashkuev, M. A. V. Logan, C. L. Hotton, and D. L. Dilcher. 2009. A probable pollination mode before angiosperms: Eurasian, long-proboscid scorpionflies. Science 326(5954): 840-847.

Strausfeld, N. J. 2009. Brain organization and the origin of insects: an assessment. Proceedings of the Royal Society of London, Series B, Biological Sciences 276(1664): 1929-1937.

Strausfeld, N. J., L. Hansen, Y. Li, R. S. Gomez, and K. Ito. 1998. Evolution, discovery, and interpretations of arthropod mushroom bodies. Learning and Memory 5(1): 11-37.

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