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1. Complex hemolymph circulation patterns in grasshopper wings

   https://doi.org/10.1038/s42003-023-04651-2  

   Salcedo, Mary K.; Jun, Brian H.; Socha, John J.; Pierce, Naomi E.; Vlachos, Pavlos P.; Combes, Stacey A. (March 2023, Communications Biology)

   Abstract An insect’s living systems—circulation, respiration, and a branching nervous system—extend from the body into the wing. Wing hemolymph circulation is critical for hydrating tissues and supplying nutrients to living systems such as sensory organs across the wing. Despite the critical role of hemolymph circulation in maintaining healthy wing function, wings are often considered “lifeless” cuticle, and flows remain largely unquantified. High-speed fluorescent microscopy and particle tracking of hemolymph in the wings and body of the grasshopperSchistocerca americanarevealed dynamic flow in every vein of the fore- and hindwings. The global system forms a circuit, but local flow behavior is complex, exhibiting three distinct types: pulsatile, aperiodic, and “leaky” flow. Thoracic wing hearts pull hemolymph from the wing at slower frequencies than the dorsal vessel; however, the velocity of returning hemolymph (in the hindwing) is faster than in that of the dorsal vessel. To characterize the wing’s internal flow mechanics, we mapped dimensionless flow parameters across the wings, revealing viscous flow regimes. Wings sustain ecologically important insect behaviors such as pollination and migration. Analysis of the wing circulatory system provides a template for future studies investigating the critical hemodynamics necessary to sustaining wing health and insect flight. 

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2. Transient use of hemolymph for hydraulic wing expansion in cicadas

   https://doi.org/10.1038/s41598-023-32533-4  

   Salcedo, Mary K.; Ellis, Tyler E.; Sáenz, Ángela S.; Lu, Joyce; Worrell, Terrell; Madigan, Michael L.; Socha, John J. (December 2023, Scientific Reports)

   Abstract Insect wings must be flexible, light, and strong to allow dynamic behaviors such as flying, mating, and feeding. When winged insects eclose into adults, their wings unfold, actuated hydraulically by hemolymph. Flowing hemolymph in the wing is necessary for functioning and healthy wings, both as the wing forms and as an adult. Because this process recruits the circulatory system, we asked, how much hemolymph is pumped into wings, and what happens to the hemolymph afterwards? Using Brood X cicadas ( Magicicada septendecim ), we collected 200 cicada nymphs, observing wing transformation over 2 h. Using dissection, weighing, and imaging of wings at set time intervals, we found that within 40 min after emergence, wing pads morphed into adult wings and total wing mass increased to ~ 16% of body mass. Thus, a significant amount of hemolymph is diverted from body to wings to effectuate expansion. After full expansion, in the ~ 80 min after, the mass of the wings decreased precipitously. In fact, the final adult wing is lighter than the initial folded wing pad, a surprising result. These results demonstrate that cicadas not only pump hemolymph into the wings, they then pump it out, producing a strong yet lightweight wing. 

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3. Toward the design of dynamically similar artificial insect wings

   https://doi.org/10.1177/1756829321992138  

   Reid, Heidi; Zhou, Huimin; Maxcer, Miles; Peterson, Robert KD; Deng, Jia; Jankauski, Mark (January 2021, International Journal of Micro Air Vehicles)

   null (Ed.)

   Flapping wing deformation influences the aerodynamics of insect flight. This deformation is dictated by the dynamical properties of the insect wing, particularly its vibration spectra and mode shapes. However, researchers have not yet developed artificial insect wings with vibration spectra and mode shapes that are identical to their biological counterparts. The goal of the present work is to develop artificial insect wings that are both isospectral and isomodal with respect to real insect wings. To do so, we characterized hawkmoth Manduca sexta wings using experimental modal analyses. From these results, we created artificial wings using additive manufacturing and heat molding. Between artificial and real wings, the first two natural frequencies differ by 7% and 16% respectively, with differences of 16% and 131% in gains evaluated at those natural frequencies. Vibration modes are similar as well. This work provides a foundation for more advanced wing design moving forward. 

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4. A simple developmental model recapitulates complex insect wing venation patterns

   https://doi.org/10.1073/pnas.1721248115  

   Hoffmann, Jordan; Donoughe, Seth; Li, Kathy; Salcedo, Mary K.; Rycroft, Chris H. (October 2018, Proceedings of the National Academy of Sciences)

   Insect wings are typically supported by thickened struts called veins. These veins form diverse geometric patterns across insects. For many insect species, even the left and right wings from the same individual have veins with unique topological arrangements, and little is known about how these patterns form. We present a large-scale quantitative study of the fingerprint-like “secondary veins.” We compile a dataset of wings from 232 species and 17 families from the order Odonata (dragonflies and damselflies), a group with particularly elaborate vein patterns. We characterize the geometric arrangements of veins and develop a simple model of secondary vein patterning. We show that our model is capable of recapitulating the vein geometries of species from other, distantly related winged insect clades. 

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5. Out from under the wing: reconceptualizing the insect wing gene regulatory network as a versatile, general module for body-wall lobes in arthropods

   https://doi.org/10.1098/rspb.2021.1808  

   Fisher, Cera R.; Kratovil, Justin D.; Angelini, David R.; Jockusch, Elizabeth L. (December 2021, Proceedings of the Royal Society B: Biological Sciences)

   Body plan evolution often occurs through the differentiation of serially homologous body parts, particularly in the evolution of arthropod body plans. Recently, homeotic transformations resulting from experimental manipulation of gene expression, along with comparative data on the expression and function of genes in the wing regulatory network, have provided a new perspective on an old question in insect evolution: how did the insect wing evolve? We investigated the metamorphic roles of a suite of 10 wing- and body-wall-related genes in a hemimetabolous insect, Oncopeltus fasciatus . Our results indicate that genes involved in wing development in O. fasciatus play similar roles in the development of adult body-wall flattened cuticular evaginations. We found extensive functional similarity between the development of wings and other bilayered evaginations of the body wall. Overall, our results support the existence of a versatile development module for building bilayered cuticular epithelial structures that pre-dates the evolutionary origin of wings. We explore the consequences of reconceptualizing the canonical wing-patterning network as a bilayered body-wall patterning network, including consequences for long-standing debates about wing homology, the origin of wings and the origin of novel bilayered body-wall structures. We conclude by presenting three testable predictions that result from this reconceptualization. 

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