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Sex allocation is one of the most studied traits in evolutionary biology because its theoretical predictions match the empirical data. Here, using the Ryukyu dry-wood termite Neotermes sugioi, we investigated several factors that could bias the sex allocation in three populations (Okinawa, Ishigaki/Iriomote, and Yonaguni). Our survey showed that there were more queen-only colonies than king-only colonies in these populations, suggesting a longer lifespan of the queens than that of the kings. In this condition, sex-asymmetric reproductive value (SRV) theory predicts female bias, because even after the short-lived kings die, the long-lived queens can continue reproduction with their sons. However, sex allocation in this species seemed to be biased toward males. Furthermore, we examined the possibility of intrasexual competition among siblings (ICS). If ICS is the cause of the bias, the allocation is expected to change depending on the total investment in sexual offspring. However, the biomass of both male and female alates increased linearly with the increase in the total biomass of the alates in these populations. Thus, neither the SRV nor the ICS theory could explain the male-biased sex ratio of N. sugioi. On the basis of these results, we discuss the remaining possibilities in this species.

Termites are major pests of houses and buildings, and also living plants such as agricultural crops, trees in forests, urban areas and gardens. However, in Japan, the basic ecology of termites nesting in living trees is not fully understood. In this study, we observed 255 colonies (nests) of the drywood termite Neotermes sugioi, collected in the field on Okinawa Island, and reported the frequency composition of the reproductive castes, the size of wood with termite gallery, the population size of colonies, and the relative position of the reproductive and non-reproductive castes within nests. Most colonies were headed by a primary queen and a primary king. However, colonies headed only by primary queens, primary kings, or neotenic kings, each accounted for approximately 5% of the colonies. A colony size of 1,000– 4,000 individuals (2058.2 ± 1695.0 [mean ± SD]) was common and the average length of colony branches was less than 100 cm. Queens and kings were found in the same or nearby nest areas, and more predominantly in the central or root side of nest wood areas. The termites may experience colony fragmentation and reproductive loss as a consequence of typhoons. Incipient colonies (i.e., colonies at an early stage of development) were found on 11.3% of branches of Leucaena leucocephala that did not show any obvious signs of infestation. In future research, it will be necessary to update the list of trees damaged by this termite species, compare the damage by tree species, and evaluate the economic impact.

Sex‐determination systems often show remarkable diversity in upstream signals, although downstream genes are broadly conserved. Therefore, the downstream genes have been investigated in various taxa, but the most upstream signals determining sex in insects have been well‐described mainly in model organisms, including fruit flies and honey bees, and not in hemimetabolous insects such as termites. Identification of sex‐linked genetic markers in termites is important to the survey of primary sex‐determination signals. Here, we report male‐specific alleles at the microsatellite locus NK12‐1 in the Ryukyu drywood termite Neotermes sugioi (Kalotermitidae). This study provides the third example of a genetic marker linked with sexual phenotype in termites, which is a small but important step to elucidate the evolutionary process of the sex‐determination system in termites., An incipient colony of Neotermes sugioi found from a twig. Our microsatellite analysis revealed male‐specific alleles at the microsatellite locus NK12‐1 in N. sugioi, which is a small but important step to elucidate the evolutionary process of the sex determination system in termites.

The synchronized dispersal of colonies is an important strategy among social insects in terms of both successful mating and the avoidance of inbreeding. Although several studies have focused on these processes in the most common termite species characterized by pulsed dispersal, only a few studies have reported on termite species characterized by continuous dispersal. Here, we describe the phenology and biological characters of the dispersal flight of Neotermes sugioi, a dry-wood termite native to the Ryukyus Islands of Japan, using five colonies isolated under semi-field conditions over a period of 183 days. We obtained evidence for the synchronicity of alate emergence among colonies of N. sugioi based on observations of synchronous patterns on the major flight and non-flight days, which showed positive correlations in alate emergence between all colony pairs. However, due to the occurrence of months with small correlation coefficients, and inconsistent alate emergence peaks among colonies on a single day, N. sugioi showed less synchronization than subterranean termites characterized by pulsed dispersal flights. Environmental conditions of temperatures and humidities greater than 22 °C and 70% were found to be necessary for high flight activity during both high and low flight seasons. In all colonies, the sex ratio of emerging alates during the observation period was significantly biased toward males. Given that adjustment of synchronous and asynchronous alate release among neighboring colonies could reduce the risk of sibling pair mating and inbreeding, the characteristic alate emergence in N. sugioi may indirectly minimize the potential for inbreeding.

Sex allocation is one of the most studied traits in evolutionary biology because its theoretical predictions match the empirical data. Here, using the Ryukyu dry-wood termite Neotermes sugioi, we investigated several factors that could bias the sex allocation in three populations (Okinawa, Ishigaki/Iriomote, and Yonaguni). Our survey showed that there were more queen-only colonies than king-only colonies in these populations, suggesting a longer lifespan of the queens than that of the kings. In this condition, sex-asymmetric reproductive value (SRV) theory predicts female bias, because even after the short-lived kings die, the long-lived queens can continue reproduction with their sons. However, sex allocation in this species seemed to be biased toward males. Furthermore, we examined the possibility of intrasexual competition among siblings (ICS). If ICS is the cause of the bias, the allocation is expected to change depending on the total investment in sexual offspring. However, the biomass of both male and female alates increased linearly with the increase in the total biomass of the alates in these populations. Thus, neither the SRV nor the ICS theory could explain the male-biased sex ratio of N. sugioi. On the basis of these results, we discuss the remaining possibilities in this species.

Termites are typical house pests that can also be harmful pests for living trees, although this topic has not received much attention. To clarify the damage to trees caused by dry-wood termites (Neotermes koshunensis), and the ecological characteristics of such damage, we conducted a study on Taiwan cherry trees (Cerasus campanulata) grown in parks, historical sites, and streets in the central-southern area of Okinawa Island, a subtropical region. Damage by N. koshunensis was confirmed in 21 of the 36 sites surveyed (58.3%) and in 76 of the 1076 trees surveyed (7.1%). However, damage by Formosan subterranean termites (Coptotermes formosanus), a house pest, was only observed at six sites (16.7%), and 10 trees (0.9%), indicating that most damage was caused by N. koshunensis. Furthermore, the probability of the presence of damaged trees close to other damaged trees was significantly higher than the probability of the presence of damaged trees close to undamaged trees, implying that destructive colonies spread from damaged trees to other trees nearby. Therefore, care for trees in the initial stages of termite invasion seems to be the best method for preventing the spread N. koshunensis damage to other trees in the same area. To our knowledge, this study is the first to report that dry-wood termite N. koshunensis are harmful pests for Taiwan cherry trees in Okinawa Island. Our results could be used to establish dry-wood termite countermeasures for garden tree species.

Differences in the dispersal flight patterns among termite families are correlated with the difference between the two life history characteristics exhibited by this group: “separate-piece nesters” versus “single-piece nesters.” However, information remains limited on the phenology and the life history characteristics of single-piece nesters, impeding our understanding of this topic. We report the flight phenology of an Asian single-piece nester termite Neotermes koshunensis on Okinawa Island, Japan. In 1983–1984, a light-trap survey showed that N. koshunensis exhibited an extended dispersal flight period from late April to early November, peaking in June, with a female-biased sex ratio. Between 1983 and 2012, the collection of 134 whole colonies of N. koshunensis from the surrounding area confirmed the presence of alates and pre-alate nymphs within the colonies over 7 months, reflecting the extended flight season of this termite species, probably in association with the extended dispersal flight season. However, in some cases, alates and pre-alate nymphs were also retained in the colonies after the dispersal flight season (i.e., winter, from December to February). The daily number of trapped alates in 1983 was positively correlated with temperature and relative humidity; however, alate production inside the colony was also positively correlated with temperature, relative humidity, and precipitation. Thus, these environmental factors might promote the flight activity of this termite by enhancing alate production inside the colony. Furthermore, temperature also had a significantly positive effect in the model incorporating the density of alates in the colony, along with environmental factors; thus, temperature might facilitate the release of alate from colonies. The accumulation of information on the phenology and life history characteristics of alate advances our understanding of the different dispersal strategies used by termites, providing insights into how the different families have evolved.

Antennal cropping, a behavior inferred to exist because queens and kings have shorter antennae than fresh alates, is widespread in termites. However, the proximate and ultimate mechanisms underlying this phenomenon remain unclear. We studied the occurrence of antennal cropping in queens and kings of the dry-wood termite Neotermes koshunensis (Kalotermitidae). Observation of the antennal tip structure with scanning electron microscopy and the occurrence of antennal cropping in new kings and queens reared in isolation indicated that self-cropping is an important proximate mechanism. Previous studies inferred that antennal cropping may play a key role in the life-history of alates at the colony-founding stage. However, we also found antennal cropping in adultoid reproductives (secondary reproductives) that had not experienced a colony founding. We propose a new hypothesis that antennal cropping is important for individuals in regulating their physiology when they change from the non-reproducing to the reproducing phase.

The Formosan termite Coptotermes formosanus Shiraki is a well-known invasive pest that causes severe damage to wooden structures in many parts of the world. Although several studies examined its phylogeographic patterns using a few mitochondrial genes, the phylogenetic relationships among C. formosanus are poorly understood because of the small number of mutations known among its mitochondrial genes. To provide a useful genetic tool for further analyses, we analyzed the complete mitochondrial genome sequence of C. formosanus using specimens collected from three isolated islands in the Ryukyu Archipelago of Japan. The circular mitogenome of these termites consisted of genes encoding 22 transfer RNAs, two ribosomal RNAs, and 13 mitochondrial proteins, as is the case for most animal mitochondrial genomes. The G + C content was 34.1%, and the total length varied slightly between 16,234 and 16,236 base pairs. The complete mitochondrial genomes of the three populations were more than 99.9% identical to each other and showed differences at six nucleotide positions. The COII, 12S rRNA, and 16S rRNA genes that are commonly used for phylogenetic analyses revealed only one substitution or no substitutions. The mitogenome sequences determined here should contribute to the design of new molecular markers for the clarification of the historical distribution process of C. formosanus and for further phylogenetic analyses with this and related termite species.