The swimming behavior of the aquatic larva of Neoneuromus ignobilis (Megaloptera: Corydalidae: Corydalinae).

In order to explore the pattern and significance of swimming, through photos and videos we observed and recorded the swimming behavior of the aquatic larvae of Megaloptera in detail for the first time using the endemic Chinese species Neoneuromus ignobilis Navas, 1932 as the test insect, which were collected from the Dadu River and reared in nature-simulated environments. Four swimming postures are recognized and described herein in detail, i. e., vertical, parallel, back and side swimming, and these postures were used by the larvae disproportionately, with a frequency of 89.08%, 5. 49%, 4. 40% and 0. 61% , respectively. The swimming larvae tend to pose their body into an S-shape, with various degree of sinuation. By changing the directions of the head and tail, they can easily rise up or sink and change swimming postures. The propulsion was generated by the wriggling of the body while the legs were mostly held close to the body. Larvae of different instars varied greatly in swimming ability, the 6th ins tar larvae being the best and most active swimmer compared to the 2nd and final instars. The larvae may also employ complex defense behaviors not often known from relatively ancient insect groups, like chemical defense as secretion from the end of abdomen

Frustrated Altermagnetism and Charge Density Wave in Kagome Superconductor CsCr3Sb5

Using first-principles density-functional calculations, we investigate the electronic structure and magnetism of the kagome superconductor CsCr$_3$Sb$_5$. At the ambient pressure, its ground state is found to be $4\times2$ altermagnetic spin-density-wave (SDW) pattern, with an averaged effective moment of $\sim$1.7$\mu_B$ per chromium atom. The magnetic long range order is coupled to the lattice structure, generating 4$a_0$ structural modulation. However, multiple competing SDW phases are present and energetically very close, suggesting strong magnetic fluctuation and frustration. The electronic states near the Fermi level are dominated by Cr-3d orbitals, and flat band or van Hove singularities are away from the Fermi level. When external pressure is applied, the energy differences between competing orders and the structural modulations are suppressed by external pressure. The magnetic fluctuation remains present and important at high pressure because the non-magnetic phase is unstable up to 30 GPa. In addition, a bonding state between Cr-3d$_{xz}$ and Sb$^{\mathrm{II}}$-p$_z$ quickly acquires dispersion and eventually becomes metallic around 5 GPa, leading to a Lifshitz transition. Our findings strongly support unconventional superconductivity in the CsCr$_3$Sb$_5$ compound above 5 GPa, and suggest crucial role of magnetic fluctuations in the pairing mechanism