To be or not to be a tibial comb: A discussion on the (past) use of tibial armature in tribal/subtribal organization in Cholevinae (Coleoptera: Leiodidae)

Detailed studies of microstructure has recently been shown to provide phylogenetic signals at several supraspecific levels within leiodid coleopterans, as well as in other insects. The tribe Ptomaphagini (Leiodidae: Cholevinae), with a Holarctic-Neotropical-Oriental distribution, has been characterized, among other things, by having a comb of equal-sized, flat spines around the apex of the tibiae of all legs, with a row of spines extending along the outer edge of the protibiae in the subtribes Baryodirina and Ptomaphaginina (but not in Ptomaphagina). A pattern similar to the one in Ptomaphaginina also occurs in the Neotropical cholevine tribe Eucatopini, and this has been used to indicate a phylogenetic relationship between the two tribes (but recent phylogenetic studies have not supported such a close relationship). We here review and revise the presence and structure of periapical (here called an ‘apical crown’) and marginal (here called an ‘external comb’) combs of spines on tibiae in Ptomaphagini, using other cholevines (with and without apical tibial combs) for comparison. We find a phylogenetic signal in an apical crown of tibial spines not interrupted at the outer spur, which seems to be an additional synapomorphy of Ptomaphagini, differing from the pattern in Eucatopini and remaining cholevines with an apical comb of spines, in which the comb is interrupted. We highlight differences not previously noticed between the apical protibial armature of Ptomaphaginina and Eucatopini

Coronal Heating as Determined by the Solar Flare Frequency Distribution Obtained by Aggregating Case Studies

Flare frequency distributions represent a key approach to addressing one of the largest problems in solar and stellar physics: determining the mechanism that counter-intuitively heats coronae to temperatures that are orders of magnitude hotter than the corresponding photospheres. It is widely accepted that the magnetic field is responsible for the heating, but there are two competing mechanisms that could explain it: nanoflares or Alfv\'en waves. To date, neither can be directly observed. Nanoflares are, by definition, extremely small, but their aggregate energy release could represent a substantial heating mechanism, presuming they are sufficiently abundant. One way to test this presumption is via the flare frequency distribution, which describes how often flares of various energies occur. If the slope of the power law fitting the flare frequency distribution is above a critical threshold, $\alpha=2$ as established in prior literature, then there should be a sufficient abundance of nanoflares to explain coronal heating. We performed $>$600 case studies of solar flares, made possible by an unprecedented number of data analysts via three semesters of an undergraduate physics laboratory course. This allowed us to include two crucial, but nontrivial, analysis methods: pre-flare baseline subtraction and computation of the flare energy, which requires determining flare start and stop times. We aggregated the results of these analyses into a statistical study to determine that $\alpha = 1.63 \pm 0.03$. This is below the critical threshold, suggesting that Alfv\'en waves are an important driver of coronal heating.Comment: 1,002 authors, 14 pages, 4 figures, 3 tables, published by The Astrophysical Journal on 2023-05-09, volume 948, page 7