A Novel Strain of Steinernema riobrave (Rhabditida: Steinernematidae) Possesses Superior Virulence to Subterranean Termites (Isoptera: Rhinotermitidae)

Subterranean termites are major global pests of wood structures and wood products. Among the most economically important subterranean termite species in the US are Heterotermes aureus, Reticulitermes flavipes, and Coptotermes formosanus. In prior studies, the entomopathogenic nematode, Steinernema riobrave strain 355, exhibited a high level of virulence to H. aureus compared with other nematode species. However, S. riobrave 355 was reported to be poorly or only moderately virulent to R. flavipes and C. formosanus, respectively. We hypothesized that other strains of S. riobrave may possess a high level of virulence to all three termite species. Under laboratory conditions we compared three novel strains of S. riobrave (3-8b, 7-12, and TP) with the 355 strain for virulence to H. aureus, R. flavipes, and C. formosanus workers. H. aureus was very susceptible to all the S. riobrave strains, and termites in all nematode treatments were dead after 4 d. The TP strain of S. riobrave caused greater mortality in R. flavipes and C. formosanus compared to the other nematode strains. Specifically, the TP strain caused 75% and 91% mortality in R. flavipes and C. formosanus, respectively, which was more than 300% and 70% higher than the mortality caused by other strains. Additional studies are warranted to determine the ability of S. riobrave (TP) to control the targeted termite species under field conditions.     

Interspecific Interactions Between Coptotermes formosanus and Reticulitermes flavipes (Isoptera: Rhinotermitidae) in Laboratory Bioassays

Experiments were conducted to examine competitive interactions between the Formosan subterranean termite, Coptotermes formosanus Shiraki (FST), and the eastern subterranean termite, Reticulitermes flavipes (Kollar) (EST), using groups of termites with different worker:soldier proportions. Experiments were conducted using three connected test chambers: an FST chamber, an unoccupied center chamber, and an EST chamber. When groups of FST were comprised of 20% soldiers versus 2% EST soldiers, only 8% of center chambers were occupied exclusively by EST. When groups of FST were comprised of 10% soldiers versus 1% EST soldiers, 44% of center chambers were occupied exclusively by EST. When the only food source was located in the center chamber, 60% of center chambers were occupied by both species. FST did not completely displace EST in any of these experiments.     

Formosan subterranean termite swarming behavior and alate sex-ratio (Isoptera: Rhinotermitidae)

Summary The Formosan subterranean termite (Coptotermes formosanus Shiraki) was first sighted in the cities of New Orleans and Lake Charles, Louisiana, in 1966. Its distribution in the historic French Quarter of New Orleans 23 years later (1989) and in 1991 and 1992 is reported here using counts of alates from light-traps. Light-trappings revealed a Quarter-wide distribution of the termite.C. formosanus shows an extended pause in flight behavior in the middle of the two-month flight season that is predictable and independent of weather. A colony-level mechanism, namely, developmental inhibition of nymphs by alates, may regulate this intermission in flight. The sex-ratio of light-trapped alates varies over time, but is generally female-biased, especially at the height of the flight season.     

Flight Speed of Tethered Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae) Alates

Alates of the Eastern subterranean termite, Reticulitermes flavipes (Kollar) were collected over two flight seasons (2002 and 2004) and flown on flight mills. Data were collected to test if alate mass, colony origin, or gender influenced flight speed. Flight speed ranged from 3.14 to 69.12 cm s⁻¹ and the maximum distance flown by an alate was 458.3 m. Alate mass (P = 0.9406), gender (P = 0.3976), colony origin (P = 0.1244), and the interaction of gender and colony (P = 0.7093) did not significantly influence flight speed. Additionally, an electronic counting device was used to provide instantaneous flight speeds and allowed flight speed to be modeled during acceleration, cruising, and deceleration periods of flight. Mean (±SEM) flight speeds in 2004 were 20.64 (±2.21) cm s⁻¹ (n = 13) for males and 17.76 cm s⁻¹ (n = 1) for the single female flown, falling within the range of the 2002 values.     

Factors that Affect Aggression Among the Worker Caste of Reticulitermes spp. Subterranean Termites (Isoptera: Rhinotermitidae)

Aggression was observed among both inter- and intraspecific combinations of four colonies of Reticulitermes flavipes (Kollar) and Reticulitermes hageni Banks in laboratory assays each month for 4 consecutive months. Termites were most frequently aggressive toward colonies of a different species. Number of individuals that displayed aggression decreased over the study period, from April to July. There was a slight trend toward reduced aggressive behavior as termites were maintained in the laboratory for 3 months. Passive and aggressive individuals were identified and reexamined for display of aggressive or passive behavior toward nonnestmates. Eighty-nine percent of previously aggressive termites displayed aggression a second time. Eighty-eight percent of previously passive termites were passive upon reexamination. Differences in head capsule size between passive and aggressive individuals provided no correlation between the presence of aggressiveness and the head capsule size in the worker caste.     

Influence of Guidelines and Passageways on Tunneling Behavior of Reticulitermes flavipes (Kollar) and R. virginicus (Banks) (Isoptera: Rhinotermitidae)

Tunneling behavior of laboratory-maintained cultures of Reticulitermes flavipes (Kollar) and R. virginicus (Banks) was examined to determine (1) if the termites build tunnels along preexisting wires or tunnels, and (2) whether tunnels are arranged to optimize search efficiency. Tunnel patterns were considered optimal if, for the number of tunnels present, the maximum area was explored. Termites entered either control arenas or arenas in which they encountered a wire or a pre-formed tunnel. Analyses revealed that R. flavipes and R. virginicus almost always follow pre-formed tunnels, but do not follow wires as readily. Within each species, the distributions of tunnels in treatment arenas were different from distributions in control arenas, most often when pre-formed tunnels were the treatment. Optimal tunnel arrangements in control arenas were found in 62% of R. flavipes patterns with 2 tunnels and in 43% of R. virginicus patterns with 2 tunnels. None of the 3-tunnel patterns from control arenas of R. flavipes and 29% of those of R. virginicus had optimal arrangements. Overall, the spatial arrangement of tunnels in control arenas was significantly different between R. flavipes and R. virginicus.     

Bioassay design and length of time in the laboratory affect intercolonial interactions of the Formosan subterranean termite (Isoptera, Rhinotermitidae)

This study examined the effect of diet, experimental design, and length of time in the laboratory on intercolonial agonism among Formosan subterranean termite, Coptotermes formosanus Shiraki, colonies. In pairings of 12 C. formosanus Shiraki colonies collected in an urban forest, there was no significant reduction in survival of termites in 30 out of 59 colony pairs compared to colony controls, but there was <50% survival in 18 colony pairs and <10% survival in six colony pairs. There was no correlation between the level of aggressive behavior and the laboratory diet of the termites. Effect of bioassay design and length of time in the laboratory was evaluated in three colony pairs where tests were first conducted on the day of field collection, then colony pairs were retested every 7 days. Aggressive behavior decreased over time in both bioassays, but it tended to decrease more rapidly in the Petri dish tests. The rapid loss of agonism in groups of termites kept in the laboratory demonstrates that changes in environmental factors affect intercolonial agonism. This article presents the results of research only. Mention of a commercial or proprietary product does not constitute endorsement or recommendation by the USDA.     

Differences in Alarm Responses in Drywood and Subterranean Termites (Isoptera: Kalotermitidae and Rhinotermitidae) to Physical Stimuli

Alarm response triggered by physical stimuli is wide spread in termites but executed in several different behavioural patterns. The drywood and subterranean termite species tested in this study differed significantly by either head-drumming or jerking when stimulated by light, air-flow, or air borne sound stimuli. Nevertheless, differences may have a common evolutionary base. Repetitive stimuli of the same quality led to reduced responses over time, which was interpreted as habituation behaviour, a simple form of learning. Adaptation as alternative explanation was ruled out because when termites were subjected with a dis-habituation-stimulus followed by the original stimulus full response occurred again to this stimulus.     

Factors affecting post-flight behavior in primary reproductives of the Formosan subterranean termite, Coptotermes formosanus (Isoptera: Rhinotermitidae)

After swarming, reproductive dealates of the Formosan subterranean termite, Coptotermes formosanus, run together in tandem. The tandem running is an age-related behavioral activity in C. formosanus. This behavior was not evoked in pre-flight alates less than 6-d-old that were artificially dealated. Female age was more important than male age for evoking tandem behavior. Females and males, older than 35 days, did not exhibit this behavior. Mating status was not important for female and male dealates to form the tandem pairs. The titers of the major tergal gland component, trilinolein, did not decline significantly and remained high, not only in virgin females, but also in mated females for a period of time after swarming. On the other hand, increasing amounts of the female-specific compound trilinolein were detected in male dealates 7, 14, and 42 days after pairing. This suggests that trilinolein in the females might be transferred to the males as a nuptial gift in C. formosanus. In addition, females have structurally different lateral setae that may constitute a morphological factor involved in the tandem behavior in this species. Covering the setae with dimethyl sulfoxide prevented the tandem behavior.     

Phylogeography illuminates maternal origins of exotic Coptotermes gestroi (Isoptera: Rhinotermitidae)

Coptotermes gestroi, the Asian subterranean termite (AST), is an economically important structural and agricultural pest that has become established in many areas of the world. For the first time, phylogeography was used to illuminate the origins of new found C. gestroi in the US Commonwealth of Puerto Rico; Ohio, USA; Florida, USA; and Brisbane, Australia. Phylogenetic relationships of C. gestroi collected in indigenous locations within Malaysia, Thailand, and Singapore as well as from the four areas of introduction were investigated using three genes (16S rRNA, COII, and ITS) under three optimality criteria encompassing phenetic and cladistic assumptions (maximum parsimony, maximum likelihood, and neighbor-joining). All three genes showed consistent support for a close genetic relationship between C. gestroi samples from Singapore and Ohio, whereas termite samples from Australia, Puerto Rico, and Key West, FL were more closely related to those from Malaysia. Shipping records further substantiated that Singapore and Malaysia were the likely origin of the Ohio and Australia C. gestroi, respectively. These data provide support for using phylogeography to understand the dispersal history of exotic termites. Serendipitously, we also gained insights into concerted evolution in an ITS cluster from rhinotermitid species in two genera.     

Alarm Reaction of European Reticulitermes Termites to Soldier Head Capsule Volatiles (Isoptera, Rhinotermitidae)

The alarm behavior of worker and soldier castes of four European subterranean termite species of the genus Reticulitermes (R. santonensis, R. lucifugus, R. grassei, R. banyulensis) is described. In petri dish bioassays we presented filter papers with squashed soldier heads as an odor source to trigger a alarm reaction. Untreated filter papers were used as controls. The behavioral patterns were alike for all four species. In the control situation (no alarm), only occasional workers and few soldiers were seen walking in the petri dish. When the odor source was presented, a general state of alertness was observed, showing as higher activity and presence, zigzag running, antennation of nestmates, jittering and jerking, mandible snapping, head-banging, and attraction to the odor source. Workers were attracted within a few seconds (6.9–13.4 s); soldiers followed much later (18.5–64.6 s). Both workers and soldiers inspected the odor source only briefly (workers for 8.7–12.8 s, soldiers for 10.0–19.5 s), with the exception of R. santonensis, where soldiers stayed an average of 209.8 s. The number of individuals, of 50 workers and 3 soldiers, near the odor source averaged 6.0–9.2 workers and 1.2–2.3 soldiers. The presence of workers is crucial: without workers, a significant alarm reaction in soldiers could not be induced. The roles of soldier and worker castes of Reticulitermes species within alarm communication and the origin and nature of possible alarm signals are discussed.     

Molecular relationships among European samples of Reticulitermes (Isoptera, Rhinotermitidae)

Taxonomy and phyletic relationships of the European termites of the holarctic genus Reticulitermes are highly debated and poorly known. Sequencing analyses of the complete cytochrome oxidase subunit II and of a fragment of 16S rDNA mitochondrial genes were performed on 21 Italian and French populations. Distance, parsimony, and maximum-likelihood evaluations on single and combined data sets confirm the presence in central peninsular Italy of R. lucifugus lucifugus, but demonstrate that a coastal Tuscan population and the Sardinian ones pertain to the Corsican subspecies R. lucifugus corsicus, whose distribution appears therefore transtyrrenian. Northeastern Italian samples are highly differentiated from presently analyzed R. lucifugus and constitute a new entity, possibly more related to the Japanese R. speratus. Finally, the French R. santonensis and the North American R. flavipes appear strongly related, so that the supposed synonymy between the two taxa must be accepted.     

Subterranean termites (Isoptera: Rhinotermitidae): Exploitation of equivalent food resources with different forms of placement

Abstract Coptotermes gestroi and Heterotermes tenuis have been described as important urban pests in Brazil. The establishment of control technologies using baits that consider the social behavior of termites requires a better knowledge of their foraging behavior. Thus, this study analyzed the feeding behavior of these species with three different forms of food placement: food on the surface of a substrate and food either partially or completely buried in the substrate. Experimental arenas were composed of a central chamber connected to three food chambers. Each central chamber contained 550 foragers of C. gestroi or 517 foragers of H. tenuis. Blocks of Pinus elliottii were placed in the different food chambers. After 28 days, the consumption of each wood block and the percentage of foraging individuals recruited for food chambers were verified in relation to the total survival rate obtained for each one of the 20 replicates. Results showed that completely buried food was most consumed for H. tenuis and presented a higher recruitment rate of workers and soldiers for both species. Although the consumption had non‐significant differences for C. gestroi, these termites exhibited a tendency to prefer completely buried food. In these conditions, it can be concluded that the forms of food placement used in the present research influenced the recruitment of individuals for both species. Data also suggests that when the foraging subterranean termites find food resources in the tunneling substrate, they tend to concentrate their efforts on it, a behavior regime that reduces exposure to external environment.     

Caste differentiation and growth of laboratory colonies of Reticulitermes urbis (Isoptera, Rhinotermitidae)

A total of 280 laboratory colonies of Reticulitermes urbis were raised for 3 years, in order to observe caste differentiation and overall colony growth, and to investigate whether the initial composition (0, 2 or 4 nymphs; 0, 5, 10, 20 or 50 workers) affected colony survival, population growth and other colony dynamics. We also wanted to determine the minimum number of individuals needed to establish a vital colony. As a result, every colony beginning with less than 20 workers died within 60 weeks, while colonies beginning with at least 20 workers survived until the end of the tests, with varied survival rates dependent upon the initial size and the time of formation (summer or autumn). The number of nymphs did not affect colony survival and colony growth. Reproductives developed from nymphs within 2 weeks and later from workers. Many of the reproductives derived from nymphs were killed by workers. The majority of the colonies contained two reproductives 3 years after initiating the tests. In addition, a few individual workers were still alive at the end of the 3-year tests. At the end of the tests, the proportion of soldiers ranged anywhere from 5.23 to 7.69% of the total population. The number of viable “juveniles” from each colony was relatively low throughout the tests and the overall population growth was not sufficient enough to replace dead workers or increase the colony size considerably. These results indicate that the potential to establish viable and sustainable colonies for groups of R. urbis composed of 5–50 workers is very low.     

Antitermitic effect of the Lantana camara plant on subterranean termites (Isoptera: Rhinotermitidae)

Abstract The insecticidal effects of Lantana camara L. (flowers, leaves, stems and roots) and the soil where lantana had been growing, on foraging activity and survival of the subterranean termites Coptotermes formosanus and Reticulitermes flavipes were examined in a 3-week experiment. The soil in which lantana had been growing had no effect on termite tunneling and survival. Incorporation of chipped fresh lantana leaves and stems into soil had no effect on mortality but caused significant reduction in tunneling. The 5-cm wide barrier of soil with lantana tissue incorporated effectively repelled groups of both species from penetrating the barrier and thus prevented infestation of a piece of wood on the other side of the barrier. C. formosanus was more sensitive in avoiding the barrier than R. flavipes. Leaves, stems and flowers were more repellent than roots. These results provide preliminary evidence that fresh-cut lantana leaves, stems and flowers may have use as additives to garden mulches against termites.     

Behavioral Interactions Between <Emphasis Type="Italic">Aphaenogaster rudis</Emphasis> (Hymenoptera: Formicidae) and <Emphasis Type="Italic">Reticulitermes flavipes</Emphasis> (Isoptera: Rhinotermitidae): The Importance of Physical Barriers

Predation pressure from ants is a major driving force in the adaptive evolution of termite defense strategies and termites have evolved elaborate chemical and physical defenses to protect themselves against ants. We examined predator–prey interactions between the woodland ant, Aphaenogaster rudis (Emery) and the eastern subterranean termite, Reticulitermes flavipes (Kollar), two sympatric species widely distributed throughout deciduous forests in eastern North America. To examine the behavioral interactions between A. rudis and R. flavipes we used a series of laboratory behavioral assays and predation experiments where A. rudis and R. flavipes could interact individually or in groups. One-on-one aggression tests revealed that R. flavipes are vulnerable to predation by A. rudis when individual termite workers or soldiers are exposed to ant attacks in open dishes and 100% of termite workers and soldiers died, even though the soldiers were significantly more aggressive towards the ants. The results of predation experiments where larger ant and termite colony fragments interacted provide experimental evidence for the importance of physical barriers for termite colony defense. In experiments where the termites nested within artificial nests (sand-filled containers), A. rudis was aggressive at invading termite nests and inflicted 100% mortality on the termites. In contrast, termite mortality was comparable to controls when termite colonies nested in natural nests comprised of wood blocks. Our results highlight the importance of physical barriers in termite colony defense and suggest that under natural field conditions termites may be less susceptible to attacks by ants when they nest in solid wood, which may offer more structural protection than sand alone.     

Escape Behavior of the Formosan Subterranean Termite (Isoptera: Rhinotermitidae) in Response to Disturbance

Disturbances to monitors and baits have often been noted as a confounding factor for the success of termite baiting systems. We studied escape behavior of Coptotermes formosanus Shiraki to a food source disturbance in the laboratory. Four peripheral chambers connected to the central food chamber through tubes served as escape routes from which escape patterns, escape and return times and differences in soldier and worker responses were recorded. We used two sand conditions: moist and dry to test whether favorable versus unfavorable conditions change escape behavior. The post disturbance responses were video recorded for 1 h. C. formosanus quickly escaped from the central chamber when disturbed. The time taken to reach the maximum number of termites that escaped ranged from 20 s to 210 s followed by a gradual return to the disturbed chamber. The majority of the escapees returned to the disturbed area within a few minutes after evacuation in both dry and wet sand conditions. A significantly higher percentage of termites escaped in wet sand arenas (43%) than in the dry sand arenas (31%). Our experiments demonstrate that C. formosanus is highly unlikely to abandon bait stations for extensive periods of time as a result of mechanical disturbances regardless of habitat quality.     

Effect of Average Worker Size on Tunneling Behavior of Formosan Subterranean Termite Colonies

The effect of a colony's average worker size on tunneling behavior of Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) in laboratory foraging arenas was investigated. Large groups of foragers from four colonies were added to arenas and allowed to tunnel for a period of 22 days. Various aspects of the resulting tunnel galleries were analyzed using ANOVA and regression analysis. After the exclusion of one colony due to high mortality, the only parameters shown to differ significantly were tunnel width and tunnel segmentation. Larger workers tended to construct less segmented galleries with wider tunnels. Tunnel length was positively correlated to size on the first 2 days, but the relationship reversed by day 4. Tunneling on day 1 was positively correlated to the discovery of food items. Our results indicate that a foraging group's average worker size can affect tunnel pattern and that groups composed of larger workers are better tunnelers, but groups of smaller sized workers are able to make up the difference over time. Possible explanations for size-related variation in tunneling behavior are discussed.