The asymmetric mandibles of termites are hypothetically more efficient, rapid, and powerful than the symmetric mandibles of snap-jaw ants or termites. We investigated the velocity, force, precision, and defensive performance of the asymmetric mandibular snaps of a termite species, Pericapritermes nitobei. Ultrahigh-speed recordings of termites revealed a new record in biological movement, with a peak linear velocity of 89.7-132.4 m/s within 8.68 μs after snapping, which caused an impact force of 105.8-156.2 mN. High-speed video recordings of ball-strike experiments on termites were analysed using the principle of energy conservation; the left mandibles precisely hit metal balls at the left-tofront side with a maximum linear velocity of 80.3 ± 15.9 m/s (44.0-107.7 m/s) and an impact force of 94.7 ± 18.8 mN (51.9-127.1 mN). In experimental fights between termites and ant predators, Pe. nitobei killed 90-100% of the generalist ants with a single snap and was less likely to harm specialist ponerine ants. compared with other forms, the asymmetric snapping mandibles of Pe. nitobei required less elastic energy to achieve high velocity. Moreover, the ability of P. nitobei to strike its target at the front side is advantageous for defence in tunnels. Some invertebrates' elastic power-amplifying systems that incorporate latches and springs can overcome the physiological limits of muscle contraction and perform a powerful or rapid movement 1,2. For example, mantis shrimps (Crustacea: Stomatopoda) perform high-speed strikes to prey by using elastic energy stored in their raptorial appendages 3. Springtails (Hexapoda: Collembola) escape from enemies with quick and powerful jumps by using their springing organ 4. Many ants and termites, such as the snap-jaw ant Mystrium camillae Emery (Hymenoptera: Formicidae) 5 and the soldiers of termite Termes panamaensis (Snyder) (Blattodea: Termitidae) 6 , have mandibles that are morphologically specialised for powerful snapping attacks. The snapping speeds of the mandibular attacks of M. camillae (111.1 m/s) 5 and T. panamaensis (67 m/s) 6 are the most rapid animal movements currently reported 1,5,6 , followed by the mandible-closing movement of Odontomachus bauri Emery trap-jaw ants (64.3 m/s) 7 , the diving of gyrfalcons (58 m/s) 8 , the nematocyst discharge of jellyfish (37 m/s) 9 , and strike behaviour of mantis shrimps (31 m/s) 1. The snapping mandibles of termite soldiers have two forms: symmetric and asymmetric 10,11. T. panamaensis has two narrow and elongated symmetric snapping mandibles that press together until they slide against each other (Fig. 1a). These mandibles strike enemies along their lateral sides 6. By contrast, the asymmetric snapping mandibles of some termites are relatively short and wide, with a twisted left mandible and curved right mandible 10. The right mandible presses against the left until the two surfaces slide. Moreover, the left mandible snaps in a clockwise motion (Fig. 1b), presumably striking enemies along the front side. Additionally, asymmetric sna...

The body size of an animal plays a crucial role in determining its trophic level and position within the food web, as well as its interactions with other species. In the symbiosis between Termitomyces and fungus-growing termites, termites rely on nutrition of fungal nodules produced by Termitomyces . To understand whether the size of termites and fungal nodules are related to their partner specificity, we quantified the size of termite farmer caste, and the size and density of nodules in termite nests of four genera of fungus-growing termites, and identified their cultivated Termitomyces fungus species based on internal transcribed spacer regions and partial large subunit ribosomal RNA gene sequences. The results showed that the size and density of fungal nodules were different among Termitomyces clades and revealed a constant trade-off between size and density among clades. The nodule size of each clade has low variation and fits normal distribution, indicating that size is a stabilized trait. Moreover, we found larger termite genera cultivated Termitomyces with larger but less numerous nodules. Based on these results, we concluded that there is a size specificity between Termitomyces and fungus-growing termites, which may lead to diversification of Termitomyces as adaptations to different termite genera.