Termite Workers Research Articles

An antifungal compound secreted by termite workers, phenylacetic acid, inhibits the growth of both termite egg-mimicking fungus and entomopathogenic fungi

Social insects live in closely related family groups but face risks of intrusion and infection by pathogenic and parasitic microbes. To cope with the microbes invading their nests and feeding sites, social insects produce various types of antimicrobial substances. Subterranean termites occupy microbe-rich decaying wood and soil at high density, expanding their nest area by exploring and feeding on wood outward from the royal chamber (room for kings and queens). Although antimicrobial agents have been identified in many termite species, few studies have investigated those used by foraging workers in decaying wood under development, which is richer in microbes than the well-sterilized royal chamber and its surroundings. Here, we report that phenylacetic acid, an antifungal aromatic compound, is secreted by foraging workers of the Japanese subterranean termite Reticulitermes speratus. The compound was detected by gas chromatography–mass spectrometry analysis of ethyl acetate extracts of shelter papers infested with the workers, and antimicrobial tests demonstrated that it inhibits the germination and/or mycelial growth of the entomopathogenic fungi (Metarhizium anisopliae and Beauveria bassiana) and the termite egg-mimicking fungus Athelia termitophila. Our study provides new insights into the antimicrobial defense mechanisms of termites, including by combining different types of antimicrobial substances secreted by different castes, and thus the survival strategy of entomopathogenic and parasitic fungi in termite nests.

Termites can learn

It is generally believed that termites can’t learn and are not “intelligent”. This study aimed to test whether termites could have any form of memory. A Y-shaped test device with one release chamber and two identical test chambers was designed and constructed by 3D printing. A colony of damp wood termites was harvested from the wild. Worker termites were randomly selected for experiment. Repellent odors that could mimic the alarm pheromone for termites were first identified. Among all substances tested, a tea tree oil and lemon juice were found to contain repellent odors for the tested termites, as they significantly reduced the time that termites spent in the chamber treated with these substances. As control, a trail pheromone was found to be attractive. Subsequently, a second cohort of termites were operant conditioned by punishment using both tea tree oil and lemon juice, and then tested for their ability to remember the path that could lead to the repellant odors. The test device was thoroughly cleaned between trials. It was found that conditioned termites displayed a reduced tendency to choose the path that led to expectant punishment as compared with naïve termites. Thus, it is concluded that damp wood termites are capable of learning and forming “fear memory”, indicative of “intelligence” in termites. This result challenges established presumption about termites’ intelligence.

Neuroregulation of foraging behavior mediated by the olfactory co-receptor Orco in termites

Olfaction is critical for survival because it allows animals to look for food and detect pheromonal cues. Neuropeptides modulate olfaction and behaviors in insects. While how the neuroregulation of olfactory recognition affects foraging behavior in termites is still unclear. Here, we analyzed the change after silencing the olfactory co-receptor gene (Orco) and the neuropeptide Y gene (NPY), and then investigated the impact of olfactory recognition on foraging behavior in Odontotermes formosanus under different predation pressures. The knockdown of Orco resulted in the reduced Orco protein expression in antennae and the decreased EAG response to trail pheromones. In addition, NPY silencing led to the damaged ability of olfactory response through downregulating Orco expression. Both dsOrco- and dsNPY-injected worker termites showed significantly reduced walking activity and foraging success. Additionally, we found that 0.1 pg/cm trail pheromone and nestmate soldiers could provide social buffering to relieve the adverse effect of predator ants on foraging behavior in worker termites with the normal ability of olfactory recognition. Our orthogonal experiments further verified that Orco/NPY genes are essential in manipulating termite olfactory recognition during foraging under different predation pressures, suggesting that the neuroregulation of olfactory recognition plays a crucial role in regulating termite foraging behavior.

Effect of soldiers on vibroacoustic alarm response in workers of subterranean termites (Blattodea: Rhinotermitidae)

Effect of soldiers on vibroacoustic alarm response in workers of subterranean termites (Blattodea: Rhinotermitidae)

Evaluation of fumigant toxicity of cyclohexanone to 5 species of insect pests.

Cyclohexanone is a major precursor for nylon production and is also used as a pesticide solvent. In this study, cyclohexanone was evaluated as a fumigant against rice weevil adults, confused flour beetle adults, western flower thrips larvae and adults, spotted wing drosophila adults, and subterranean termite workers. Cyclohexanone fumigation was effective against all 5 insects, and there were considerable variations in susceptibility to cyclohexanone fumigation among the 5 species. At 20 °C, complete control of spotted wing drosophila adults was achieved in 1-h fumigation with 25 μl/l of cyclohexanone and complete control of eastern subterranean termite workers was achieved in 3-h fumigations with 50 μl/l dose of cyclohexanone. Stored-product insects confused flour beetle, and rice weevil adults were more tolerant to cyclohexanone fumigation. Fumigations of 24 h with 75 μl/l dose of cyclohexanone caused 100% mortality of rice weevil adults and 98% mortality of confused flower beetle adults. Even at a 100 μl/l dose, the 24-h fumigations did not achieve 100% mortality of confused flour beetle adults. At 5 °C, complete control of western flower thrips was achieved in 3- and 6-h fumigations with 100 and 50 μl/l doses of cyclohexanone, respectively. Cyclohexanone vapor concentrations were measured using cyclohexanone detector tubes. Vapor concentrations were far below the expected saturation concentration indicating that most cyclohexanone did not exist as vapor in fumigation chambers. The results of effective control of all 5 insect species suggest that cyclohexanone has the potential to be used as a fumigant for postharvest pest control.

Pemanfaatan Air Leri dan Air Mikroorganisme Lokal Sebagai Pengendali Rayap Tanah

Termites (Coptotermes curvignathus) are considered more dangerous than other termite species as they can cause significant damage to plantation and agricultural crops, with widespread distribution. The use of chemical pesticides to control this pest can lead to resistance and have negative impacts on the environment and human health. An environmentally friendly solution involves utilizing natural plants/substances as botanical insecticides, such as rice washing water and local microorganism (MOL) water. The aim of this research is to evaluate the effects of these two substances on termite population control and determine the optimal formulation that can act as a termite repellent. and to determine the optimal formulation as an anti-termite. The research methodology involves determining formulations of botanical insecticides, namely 100% rice washing water, 100% MOL water, 50% rice washing water : 50% MOL water, 75% rice washing water : 25% MOL water, 25% rice washing water : 75% MOL water. Each test box is filled 5 soldier termites and 20 worker termites, then provided with test papers that have been soaked in the predetermined formulation. Each treatment is repeated three times and observed every 24 hours for 72 hours. The research results indicate that all formulations uses did not have a significant impact on termite mortality. It can be concluded that the use of rice washing water and MOL water in the tested formulations is not effective as an insecticide to control termite.

ISOLATION, IDENTEFECATION AND EFFECINCY OF PSEUDOMONAS FLUORESCENS BACTERIA TO TERMITE MICROCEROTERMIS DIVERSUS

This study was conducted to isolate the bacteria Pseudomonase fluorescens from the termite, locust, and American cockroach in the Iraqi environment and to diagnose it based on morphological, biochemical, and molecular diagnosis using the polymerase chain reaction (PCR), as well as test its pathogenicity and efficacy to termites under laboratory conditions. The results of morphological , biochemical, and molecular diagnosis using polymerase chain reaction (PCR) tests showed the isolated bacterial isolates are similar to P. fluorescens .The results of efficiency of different isolates of P. fluorescens showed that they have a high pathogenicity towards termite workers in laboratory and incubation condition.

Pengaruh Air Cucian Beras dan Air Mikroorganisme Lokal Terhadap Mortalitas Rayap Tanah

Subterranean termites (Coptotermes curvignathus) are dangerous termites compared to other types of termites because thay cause damage to crops in plantations and agriculture and have a wide distribution. The use of chemical pesticides causes pests to become resistant and harmful to the environment and health. Botanical pesticides are used as an alternative solution that is environmentally friendly by utilizing leri water and MOL water. This research aims to determine the effect of leri water and lokal microorganism ater (MOL) to control subterranean termites and to determine the optimal formulation as an anti-termite. The research method using 5 formulations of botanical pesticide, namely 100% leri water, 100% MOL water, 50% leri water : 50% MOL water, 75% leri water : 25% MOL water, 25% leri water : 75% MOL water and control (without formulation). Each test container contains 5 soldier termites and 20 worker termites and is given a filter paper test that has been soaked with a predeterminated formulation. Each treatment was replicated 3 times and observed every 24 hours for 72 hours. The results showed that all formulations had no effect on subterranean termite mortality.

Uncovering the Chemosensory System of a Subterranean Termite, Odontotermes formosanus (Shiraki) (Isoptera: Termitidae): Revealing the Chemosensory Genes and Gene Expression Patterns.

Termites are eusocial insects. Chemical signals between colony members are crucial to the smooth running of colony operations, but little is known about their olfactory system and the roles played by various chemosensory genes in this process. Chemosensory genes are involved in basic olfactory perception in insects. Odontotermes formosanus (Shiraki) is one of the most damaging pests to agricultural crops, forests, and human-made structures. To better understand the olfactory system and the genes involved in olfactory processing in O. formosanus, we produced a transcriptome of worker termites. In this study, we identified 13 OforOBPs, 1 OforCSP, 15 OforORs, 9 OforGRs, and 4 OforSNMPs. Multiple sequence alignments were used in the phylogenetic study, which included data from other termite species and a wide variety of insect species. Moreover, we also investigated the mRNA expression levels using qRT-PCR. The significantly high expression levels of OforCSP1, OforOBP2, OforOR1, and OforSNMP1 suggest that these genes may play important roles in olfactory processing in termite social behavior, including caste differentiation, nestmate and non-nestmate discrimination, and the performance of colony operations among members. Our research establishes a foundation for future molecular-level functional studies of chemosensory genes in O. formosanus, which might lead to the identification of novel targets for termite integrated pest management.

Step-by-step Dissection Protocol of Apicotermitinae Worker (Blattaria: Isoptera)

Apicotermitinae are soldierless termites highly abundant in tropical forests. The taxonomy of this subfamily is based on characters of worker cast and winged forms when present. However, the procedures necessary to dissect termite workers to observe their external and internal morphological characteristics are not well detailed in any study. Here, we describe a step-by-step protocol for worker dissection of soldierless termite species. We suggest the use of Polyvinyl Alcohol (PVA) for cleaning and visualization of the gizzard and enteric valve, and glycerin to remove tergites and sternites and describe in detail the dissection of the gizzard and enteric valve, and how visualize the insertion of Malpighian tubules.

Time-dependent mortality and behavioral response of Odontotermes obesus (Blattodea: Termitidae) against different dose rates of pesticides for sustainable forest management

Termites have become a global concern, and their effective management has remained a challenge since time immemorial. Certain microbial and botanical agents have been used for their management, but their efficacy has been compromised, particularly in field conditions. Hence, the current study was designed to check the efficacy of low doses of different pesticides, such as chlorpyrifos, fipronil, bifenthrin, and chlorantraniliprole, against mortality and behavioral responses of Odontotermes obesus at two different temperatures (16 ± 1 and 26 ± 1°C). The discrete behavioral symptoms included intoxication, ataxia, moribundity, and death. Laboratory-maintained termite workers were exposed to different concentrations of pesticides through a filter paper bioassay. All tested pesticides and their concentrations differed significantly regarding their lethal time (LT50) values compared to the mortality of termite workers. Moreover, the LT50 values of pesticides gradually decreased with increased pesticidal concentrations. Temperature also had a significant effect on the efficacy of tested pesticides as all pesticides showed better results at higher temperatures. At both tested temperatures, chlorantraniliprole (5 ppm) proved to be the most effective pesticide against termite workers. Similarly, the behavioral symptoms also varied depending on pesticides and their administered concentrations and existed for a relatively longer time span at lower temperatures. In most cases, the order of responses was moribundity, followed by intoxication and ataxia. Moribundity and intoxication were the most frequently observed symptoms for chlorpyriphos and bifenthrin-treated termite workers. In the case of fipronil, intoxication was the most pronounced symptom. Similarly, the maximum value of ataxia was recorded in the case of chlorantraniliprole. However, moribund symptoms lasted longer in all tested concentrations of chlorantraniliprole, followed by ataxia and intoxication. The overall order of toxicity was chlorantraniliprole > bifenthrin > fipronil > chlorpyrifos. These pesticides, at their low doses, did not exhibit any repellent action and were not detected by the foraging termite workers. Moreover, their slow action mechanism makes them a suitable candidate for infecting whole colonies away from treated surfaces. Therefore, these pesticides can be successfully incorporated into different integrated termite management programs to keep the plantation free from threatening underground pests.

Evolution of a Cockroach Allergen into the Major Protein of Termite Royal Jelly.

Termites live in colonies, and their members belong to different castes that each have their specific role within the termite society. In well-established colonies of higher termites, the only food the founding female, the queen, receives is saliva from workers; such queens can live for many years and produce up to 10,000 eggs per day. In higher termites, worker saliva must thus constitute a complete diet and therein resembles royal jelly produced by the hypopharyngeal glands of honeybee workers that serves as food for their queens; indeed, it might as well be called termite royal jelly. However, whereas the composition of honeybee royal jelly is well established, that of worker termite saliva in higher termites remains largely unknown. In lower termites, cellulose-digesting enzymes constitute the major proteins in worker saliva, but these enzymes are absent in higher termites. Others identified a partial protein sequence of the major saliva protein of a higher termite and identified it as a homolog of a cockroach allergen. Publicly available genome and transcriptome sequences from termites make it possible to study this protein in more detail. The gene coding the termite ortholog was duplicated, and the new paralog was preferentially expressed in the salivary gland. The amino acid sequence of the original allergen lacks the essential amino acids methionine, cysteine and tryptophan, but the salivary paralog incorporated these amino acids, thus allowing it to become more nutritionally balanced. The gene is found in both lower and higher termites, but it is in the latter that the salivary paralog gene got reamplified, facilitating an even higher expression of the allergen. This protein is not expressed in soldiers, and, like the major royal jelly proteins in honeybees, it is expressed in young but not old workers.

Foraging proportion of the Formosan subterranean termite workers and soldiers in relation to soil type

A colony of subterranean termites contains different castes such as workers and soldiers that perform various tasks. Foraging activity is vital among many tasks of a colony and ~20% of the worker population in a colony of Coptotermes formosanus engage in foraging. Although flexibility in task allocation plays a crucial role in maintaining colony function in fluctuating environments, such flexibility is barely understood in subterranean termites. Here, we investigated regulations of foraging task allocation in response to different soil types at the nest and the foraging site. At the nest and foraging site, either nitrogen-rich organic soil or nitrogen-poor sand, which differed in carbon and nitrogen ratio, was provided and the proportions of workers and soldiers at the foraging site were determined. Our results showed that the foraging worker proportion and per-capita wood consumption significantly differed depending on the soil type at the nest but not the soil type at the foraging site. When the colony had access to organic soil at the nest, the proportion of workers at the foraging site and per-capita wood consumption was much smaller than those with sand at the nest. Conversely, the proportion of soldiers at the foraging site remained the same regardless of the soil type at the nest and the foraging site. In brief, the current study showed flexible regulation of foraging task allocation in C. formosanus and demonstrated that perturbation of soil type alters the allocation of workers, but not soldiers, in the colony.

Abundance, occurrence and time series: long-term monitoring of social insects in a tropical rainforest

The magnitude of worldwide insect decline is hotly debated, with multiple examples of stable or increasing insect populations. In addition, time series data for tropical insects are scarce, notably in rainforests where insect diversity is poorly known but reaches a peak. Despite social insects (ants, termites, bees and allies) being key organisms in these habitats, long-term monitoring data for these groups are crucially lacking. For many of these insects, the difficulty of locating nests in rainforests could be one reason. In this context, species occurrence in samples is often used as a surrogate for abundance to evaluate species distribution in space/time, but the loss of information is difficult to assess. In a tropical rainforest in Panama, we employed various sampling methods to examine the time series of seven insect assemblages with differing degrees of sociality: termite workers and soldiers, termite alates, bess beetles, litter ant workers, army ant alates, orchid bees, and nocturnal sweat bees. We used five community variables and six models related to occurrence and abundance, to test for significant trends in assemblages over a 13-year period (2009–2021). While assemblages of bess beetles increased, those of termite workers and soldiers, army ant alates, and orchid bees remained relatively stable. Termite alate, litter ant worker, and nocturnal bee assemblages showed signs of decline, demonstrating the need for monitoring distinct assemblages. Significant trends in generalized additive mixed models (GAMM) were observed in three out of five assemblages that could be tested. Our study indicates that trends in assemblages may be more informatively reported with abundance than with occurrence. We recommend (1) monitoring multiple insect assemblages as ecological indicators responsible for diverse ecosystem services; and (2) reporting species richness, changes in faunal composition, occurrence, and, when possible, using time-explicit analyses (such as GAMM models) for evaluating population trends over time.

Gene expression profiles of chemosensory genes of termite soldier and worker antennae.

Termites have an elaborate social system that involves cooperation and division of labour among colony members. Although this social system is regulated by chemical signals produced in the colony, it remains unclear how these signals are perceived by other members. Signal transduction is well known to be triggered by the reception of odorant molecules by some binding proteins in the antennae, after which, a signal is transmitted to chemosensory receptors. However, there is insufficient information on the role of chemosensory genes involved in signal transduction in termites. Here, we identified the genes involved in chemosensory reception in the termite Reticulitermes speratus and performed a genome-wide comparative transcriptome analysis of worker and soldier antennae. First, we identified 31 odorant-binding proteins (OBPs), and three chemosensory protein A (CheA) from the genome data. Thereafter, we performed RNA sequencing to compare the expression levels of OBPs, CheAs, and previously identified chemosensory receptor genes between worker and soldier antennae. There were no receptor genes with significant differences in expression between castes. However, the expression levels of three non-receptor odorant-detection/binding proteins (OBP, CheA, and Sensory neuron membrane protein) were significantly different between castes. Real-time qPCR (RT-qPCR) analysis using antennae and other head parts confirmed that these genes were highly expressed in soldier antennae. Finally, independent RT-qPCR analysis showed that the expression patterns of these genes were altered in soldiers from different social contexts. Present results suggest that gene expression levels of some non-receptors are affected by both castes and behavioural interactions among colony members in termites.

Do the foraging strategies of Odontotermes horni (Wasmann)workers on various organic matter depend on the weather parameters?

The investigation delved into how worker termites of O. horni search for food sources under varying weather conditions in an undisturbed forest ecosystem. The result indicated that the maximum atmospheric temperature had a significant negative correlation with foraging patches < 25 cm. The minimum atmospheric temperature exhibited a significant negative correlation with tree damage and the height of earthen sheeting construction by the termite workers. Moreover, the maximum atmospheric relative humidity showed a significant negative correlation with tree damage and the height of earthen sheeting by the workers. Similarly, the minimum atmospheric relative humidity had a significant negative relationship with tree damage and the height of earthen sheeting construction by the workers, but a positive significant relationship with foraging patches < 25 cm. Lastly, rainfall had a significant negative relationship with tree damage and the height of earthen sheeting on the trees, while sunshine hours showed a significant positive relationship with tree damage by the workers.

Impact of Odontotermes horni workers foraging on the loss of organic matter in agro and forest ecosystem

The study aimed to analyze the effect of worker termites of O. horni on the organic litter of finger millet crops cultivated under dryland agroecosystems and silver oak leaves in the forest ecosystem. The findings indicated that there was a depletion of 221.90 g and 113.72 g of organic litter per m2 area, with a maximum loss of 66.66% and 60.29%, respectively, in the unprotected finger millet plots and silver oak plantations.

Foraging strategies of the workers of Odontotermes horni on various organic matter

The study focused on how worker termites of O. horni forage for different food sources. They were found to forage under earthen sheetings of various shapes and sizes, depending on the foraging site and season. Active foraging was observed during cooler hours of the day. This species is efficient in harvesting food without wasting energy while transporting either food or soil particles on the tree trunk.

The root stubble loss due to foraging by the workers of Odontotermes horni on different crops under dryland agroecosystem.

The study was mainly focused on the foraging behavior of worker termites of O. horni on various crops grown under dryland agroecosystems and how they cause loss to root stubbles. The results showed that soybean had the highest loss to root stubbles at 88.62%, followed by maize at 73.72% and finger millet at 70.16%. In terms of partial root stubble loss, maize had the highest percentage at 26.54%, followed by finger millet at 21.82% and soybean at 3.01%. On the other hand, complete root stubbles eaten by the workers were more in soybean at 86.61%, followed by maize at 57.84% and finger millet at 55.85%.

Biocontrol Potential of Entomopathogenic Nematodes against Odontotermes obesus (Blattodea: Termitidae) under Laboratory and Field Conditions

Odontotermes obesus (Blattodea: Termitidae) is a prevalent subterranean wood-eating termite species that causes damage to mature trees, saplings and seedlings. The efficacy of most synthetic insecticides against this notorious pest has been compromised primarily because of its enigmatic feeding behavior and development of resistance to a number of insecticides. It has therefore become necessary to explore other alternative biologically sound and low-impact termite control methods, particularly for use in forests. Hence, this study was designed to verify the efficacy of different indigenous EPN isolates (Steinernema carpocapsae, Heterorhabditis bacteriophora and Heterorhabditis indica) against workers of Odontotermes obesus. The pathogenicity of each nematode isolate was assessed in laboratory conditions using filter paper and sawdust bioassay at two different temperatures (16 ± 1 and 26 ± 1 °C). Additionally, the efficacy of the nematode species was also assessed in field conditions. The results of the experiments revealed that the mortality of termite workers was more pronounced in sawdust bioassay in comparison with filter paper bioassay at both the tested temperatures. The mortality response in both bioassays was more pronounced at the higher temperature. A significantly higher mortality was recorded at both tested temperatures for S. carpocapsae followed by H. bacteriophora and H. indica. A dose-dependent positive mortality response was also recorded at both tested temperatures. Similar to the laboratory trials, the field applications of the three tested nematode species showed that maximum mortality was recorded for S. carpocapsae followed by H. bacteriophora and H. indica. It was therefore concluded that indigenous EPNs can provide more effective control of termites, possibly because of their direct interaction with pest species in the soil and the possibility of causing secondary infection through infected cadavers.