Effects of Menadione on Survival, Feeding, and Tunneling Activity of the Formosan Subterranean Termite

The Formosan subterranean termite, Coptotermes formosanus Shiraki, is a highly destructive pest and a cosmopolitan invasive species. Sustainable termite management methods have been improving with the search for novel insecticides that are effective, safe, and cost efficient. Menadione, also known as vitamin K3, is a synthetic analogue and biosynthetic precursor of vitamin K with low mammalian toxicity. Menadione has shown insecticidal activity in several insects, presumably due to interference with mitochondrial oxidative phosphorylation. However, little is known about its effectiveness against termites. In this study, we evaluated the toxicity and repellency of menadione in C. formosanus. Our results showed that menadione affected the survival and feeding activity of termites both in filter paper and substrate (sand) treatments, and menadione influenced termite tunneling activity in treated sand. In a no-choice assay, ≥90% mortality after seven days and minimal or no food consumption were recorded when sand was treated with menadione at 6 to 600 ppm. In a two-choice assay with a combination of treated and untreated sand, termites were deterred by menadione at 6 to 600 ppm and exhibited low mortality (≤30%) over seven days, while tunneling activity was prevented with 60 to 600 ppm of menadione treatment. Overall, our study demonstrated dose-dependent toxicity and repellency of menadione in C. formosanus. The potential use of menadione as an alternative termite control agent is discussed.

Comparative Antennal Morphometry and Sensilla Organization in the Reproductive and Non-Reproductive Castes of the Formosan Subterranean Termite

Antennae are the primary sensory organs in insects, where a variety of sensilla are distributed for the perception of the chemical environment. In eusocial insects, colony function is maintained by a division of labor between reproductive and non-reproductive castes, and chemosensation is essential for regulating their specialized social activities. Several social species in Hymenoptera display caste-specific characteristics in antennal morphology and diversity of sensilla, reflecting their differential tasks. In termites, however, little is known about how the division of labor is associated with chemosensory morphology among castes. Using light and scanning electron microscopy, we performed antennal morphometry and characterized the organization of sensilla in reproductive (female and male alates) and non-reproductive (worker and soldier) castes in the Formosan subterranean termite, Coptotermes formosanus Shiraki. Here, we show that the antennal sensilla in alates are twice as abundant as in workers and soldiers, along with the greater number of antennal segments and antennal length in alates. However, all castes exhibit the same types of antennal sensilla, including basiconicum, campaniformium, capitulum, chaeticum I, chaeticum II, chaeticum III, marginal, trichodeum I, and trichodeum I. The quantitative composition of sensilla diverges between reproductive and non-reproductive castes, but not between female and male alates or between worker and soldier castes. The sensilla display spatial-specific distribution, with basiconicum exclusively and capitulum predominantly found on the ventral side of antennae. In addition, the abundance of chemosensilla increases toward the distal end of antennae in each caste. This research provides morphological signatures of chemosensation and their implications for the division of labor, and suggests future neurophysiological and molecular studies to address the mechanisms of chemical communication in termites.

Genetic Analysis of Formosan Subterranean Termite (Blattodea: Rhinotermitidae) Populations in California

A new infestation of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Blattodea: Rhinotermitidae), was discovered in Canyon Lake, Riverside County, California. We used three mitochondrial DNA (COI, COII, and 16S) and seven polymorphic microsatellite markers to characterize the genetic relationship of the colony with two other colonies that were collected in 1992 and 2018 in La Mesa, San Diego County. Maximum likelihood phylogeny of C. formosanus based on concatenated COI and COII sequences revealed that the two La Mesa populations (CA01 and CA02) and the Canyon Lake population (CA03) were from different maternal lineages. Based on the 14 COII haplotypes of C. formosanus found world-wide, CA01 and CA02 belonged to a haplotype widely distributed across the United States, while CA03 was grouped under a haplotype predominantly found in Asia. Microsatellite allele frequencies across all loci for both La Mesa populations were relatively similar, but significant genetic differences were found between CA02 and CA03 colonies (FST = 0.24; Dest = 0.30; G″ ST = 0.55; P < 0.01).

Coptotermes formosanus (Blattodea: Rhinotermitidae) established in Israel and world distribution of a major termite pest

The Formosan subterranean termite, Coptotermes formosanus Shiraki, 1909, is a highly destructive structural pest endemic to East Asia. We report a land-based establishment of C. formosanus in Petah Tikva, Israel, over 6000 km from its nearest previous locality in China. The species’ identity was confirmed by soldier morphology and by COI sequence data. In addition, a population discovered in 1992 in suburban San Diego, California, USA, remains viable. Marathon hosts the first infestation of C. formosanus in the Florida Keys. The world distribution of C. formosanus is presented, and the biogeography and mechanisms of spread of this termite are discussed.

Redescription of Formosan subterranean termite, Coptotermes formosanus (Blattodea: Rhinotermitidae), with three new synonyms from China

The Formosan subterranean termite, Coptotermes formosanus Shiraki, 1909, is an important structural pest in Mainland China, Japan, Taiwan, Bahamas, and the United States. Coptotermes formosanus was first described in Japanese, and the morphological description was too simple for congeneric species differentiation, resulting in confusion in species identification. To date, ten junior synonyms of C. formosanus have been reported. To avoid further confusion, we redescribed C. formosanus based on the type specimen and the specimens from the type locality, Taiwan. Most of the Coptotermes Wasmann, 1896 taxonomy has been clarified worldwide and the Chinese case remains an outlier, with many species that need to be revised. We further examined the taxonomic statuses of four Chinese species, C. chang­taiensis Xia & He, 1986, C. hekouensis Xia & He, 1986, C. shanghaiensis Xia & He, 1986, and C. suzhouensis Xia & He, 1986. We proposed that C. changtaiensis, C. hekouensis, and C. suzhouensis are the junior synonyms of C. formosanus. Even though the morphological characters of C. shanghaiensis are similar to C. formosanus, the body size of the former is significantly smaller. Additional Coptotermes samples collected from the Shanghai area would be required for the taxonomic status of C. shanghaiensis to be confirmed.