Revision of the termite family Rhinotermitidae (Isoptera) in New Guinea

Recently, we completed a revision of the Termitidae from New Guinea and neighboring islands, recording a total of 45 species. Here, we revise a second family, the Rhinotermitidae, to progress towards a full picture of the termite diversity in New Guinea. Altogether, 6 genera and 15 species are recorded, among which two species, Coptotermes gambrinus and Parrhinotermes barbatus, are new to science. The genus Heterotermes is reported from New Guinea for the first time, with two species restricted to the southern part of the island. We also provide the first New Guinea records for six species of the genera Coptotermes and Schedorhinotermes. We briefly describe soldiers and imagoes of each species and provide a key based on soldier characters. Finally, we discuss the taxonomic and biogeographical implication of our results. A replacement name, Schedolimulus minutides Bourguignon, is proposed for the termitophilous staphylinid Schedolimulus minutus Bourguignon, to solve a question of secondary homonymy.     

Reproductive mechanisms and dynamics of habitat colonization in Microcerotermes biroi (Isoptera: Termitidae)

Abstract. 1. Previous studies on the arboreal termite community in coconut plantations of northern New Guinea showed that Microcerotermes biroi is the most abundant species, despite the fighting superiority of two competitor species Nasutitermes princeps and N.novarumhebridarum. In this study we tested the hypothesis that the success of M.biroi is due to its efficiency at colonizing new habitats following nuptial flights.
2. We demonstrated experimentally the ability of M.biroi colonies to replace their reproductives when removed, or to produce reproductives in satellite nests when isolated from the remainder of the colony. Replacement reproductives were always neotenics, derived from nymphs or workers.
3. Despite the ability of neotenics to differentiate within their home colonies, 84% of field colonies were headed by dealated imagos. This value constitutes a minimum estimate of the proportion of field colonies founded independently by imagos after the nuptial flight.
4. The monitoring of a young plantation during the first 31/2 years of its colonization by arboreal nesting termites revealed its invasion by M.biroi , which colonized 63% of the trees while neither Nasutitermes species appeared.
5. Our results demonstrate that M.biroi is actually a pioneer species, able to invade a new habitat by means of nuptial flights. They outline the importance of each species' reproductive strategy in shaping the arboreal-nesting termite community.     

Patterns of neotenic differentiation in a subterranean termite, Reticulitermes speratus (Isoptera: Rhinotermitidae)

Plasticity in the caste developmental pathway is a remarkable characteristic of termite societies. In Reticulitermes, two types of neotenic reproductive, nymphoids and ergatoids, may differentiate from nymphs and workers and take over reproduction in the colony after the death of the original primary reproductive pair. We examined the dynamics of newly differentiated nymphoids and ergatoids in experimentally orphaned laboratory colonies of R. speratus with different caste compositions. The period required for differentiation of nymphoids was shorter than that for differentiation of ergatoids. The sex ratio of neotenics was strongly female‐biased, particularly in ergatoids. The results suggested that the number of differentiated ergatoids was restricted by the existence of nymphs or nymphoids in a colony. Workers were assumed to kill most newly differentiated neotenics. Attack reflecting conflict between colony members is probably an important mechanism to control neotenic emergence.     

Temporal and geographic variations in the morphology and chemical composition of the frontal gland in imagoes of Prorhinotermes species (Isoptera: Rhinotermitidae)

Although the frontal gland has long been known as a prominent defensive device for termite soldiers in many Rhinotermitidae and Termitidae, almost nothing is known about its function in imagoes. In the present study, we show that the frontal gland of imagoes in Prorhinotermes species is well developed at the time of the nuptial flight, and is filled with a complex mixture of sesquiterpene hydrocarbons and nitroalkenes. The sesquiterpene composition varies between Prorhinotermes simplex and Prorhinotermes canalifrons , between geographically distant colonies of P. simplex (Cuba versus Florida), and even between different flights of closely-related subcolonies. The ratio between ( E )-1-nitropentadec-1-ene and sesquiterpenes is sex-specific. The volume of secretory cells decreases in functional kings and queens after colony foundation, and the subcellular organization changes into a form resembling unmodified epidermal cells. Dealate reproductives lose the ability for biosynthesis, and their frontal gland is devoid of volatile compounds found in swarming imagoes. The results obtained in the present study clearly show that the frontal gland is only temporarily active at the time of the dispersal flight. The most likely function of this gland is defence by the toxic nitroalkenes.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 384–392.     

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.     

Field observations of intercolony aggression and territory changes inHeterotermes aureus (Isoptera: Rhinotermitidae)

Intercolony aggression was observed for a southwestern desert subterranean termite, Heterotermes aureus(Snyder), in bait plots in a Sonoran Desert grassland in Arizona. Intermittent conflict took place at the sites of corrugatedpaper rolls on the boundary between two colonies. Rows of dead termites locked in combat were found within the corrugations, with additional dead termites usually in the soil beneath the roll. Dead soldiers constituted 64 to 100% of termites recovered from sites of intercolony conflict. Ongoing intercolony aggression is likely involved in the maintenance of discrete H. aureusterritories.     

Trail Communication During Foraging and Recruitment in the Subterranean Termite Reticulitermes santonensis De Feytaud (Isoptera, Rhinotermitidae)

The search for food in the French subterranean termite Reticulitermes santonensis De Feytaud is organized in part by chemical trails laid with the secretion of their abdominal sternal gland. Trail-laying and -following behavior of R. santonensis was investigated in bioassays. During foraging for food termites walk slowly (on average, 2.3 mm/s) and lay a dotted trail by dabbing the abdomen at intervals on the ground. When food is discovered they return at a quick pace (on average, 8.9 mm/s) to the nest, laying a trail for recruiting nestmates to the food source. While laying this recruitment trail the workers drag the abdomen continuously on the ground. The recruitment trail is highly attractive: it is followed within a few seconds, by more nestmates, and at a quicker pace (on average, 6.4 mm/s) than foraging trails (on average, 2.9 mm/s). The difference between foraging and recruitment trails in R. santonensis could be attributed to different quantities of trail pheromone. A caste-specific difference in trail pheromone thresholds, with workers of R. santonensis being more sensitive to trails than soldiers, was also documented: soldiers respond only to trails with a high concentration of trail pheromone.     

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.     

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.     

Long-term impact of orphaning on field colonies ofCoptotermes lacteus (Froggatt) (Isoptera: Rhinotermitidae)

Summary Colonies ofCoptotermes lacteus (Froggatt) from a site in coastal south-eastern Australia were experimentally orphaned in early 1989. Sample colonies were examined 3, 6, 12, 18, 24 or 30 months later for their caste composition, the presence of replacement reproductives and brood. All replacement reproductives were nymphoid neotenics. The number of functional (physogastric) females ranged from 1 to 27; this variability was maintained irrespective of the length of time between orphaning and inspection of the colonies. The average live mass of individual females stayed at 30 to 40 mg over the period of 6 to 30 months after orphaning in groups of more than five neotenic queens, but increased from 38 mg three months after orphaning to about 125 mg after 24 months in colonies headed by fewer than five neotenic females. The combined live mass of neotenic females could approach or even exceed that of primary queens. Two key features characterized experimentally and naturally orphaned, neotenic-headed colonies: (1) Nymphs differentiated in significant numbers all year round for a period of at least 30 months right from the time neotenics commenced breeding (in primary-headed colonies nymph production is strictly seasonal). (2) All or most nymphs were males (in primary-headed colonies the sex ratio of nymphs is more or less balanced). The mechanism(s) for achieving the male-biased sex ratio is (are) unknown. Even when colonies have resumed breeding with the help of neotenics, colony survival is not guaranteed. Under such circumstances the gene pool is best preserved if colonies were to raise and release large numbers of alates as potential founders of new colonies. By producing largely male nymphs orphaned colonies ensure outbreeding and may prevent competition (and its disruptive impact an breeding) between existing reproducing neotenic queens and newly differentiating female neotenics. Competition between male neotenics is unlikely to have any impact on the rate of brood production and therefore would not require a mechanism to prevent it from occurring.     

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.     

Effects of antibiotics on hydrogen production and gut symbionts in the Formosan subterranean termite Coptotermes formosanus (Isoptera: Rhinotermitidae)

Abstract Symbiotic microorganisms that inhabit the gut of Coptotermes formosanus enable this termite to degrade lignocelluloses and further produce hydrogen as an important intermediate to be recycled in its hindgut or as a byproduct to be emitted to the atmosphere. Both symbiotic protists and prokaryotes in the guts of termites demonstrated some different roles with respect to hydrogen production. In this study, the effects of two antibiotics, ampicillin and tetracycline, on hydrogen emission and the gut symbionts of C. formosanus were investigated. Hydrogen emission from termite guts was significantly enhanced when termites fed on wood diets treated with either ampicillin or tetracycline. The greatest H₂ emission rates, 2 519 ± 74 and 2 080 ± 377 nmol/h/g body weight, were recorded with the treatments of ampicillin and tetracycline, respectively, which showed 6–7 times more H₂ production than that of controls. Antibiotic‐treated diets negatively affected the prokaryotic communities and reduced their abundances, particularly on those ectosymbionts inhabiting the gut walls or in the gut fluid of C. formosanus, such as spirochetes. However, no significant reductions in the counts of gut cellulolytic protists, Pseudotrichonympha grassii and Holomastigotoids hartmanni, were recorded; and with a further observation by confocal laser scanning microscopy, the endosymbionts inhabiting P. grassii generally survived the antibiotic treatments. These results suggest that some prokaryotes may serve as the main hydrogen consumers, while P. grassii, together with its endosymbionts, may function as the main contributors for hydrogen production in the hindgut of C. formosanus.     

Panic escape polyethism in worker and soldier Coptotermes formosanus (Isoptera: Rhinotermitidae)

Termites were the first animal to form societies. Two hundred million years of evolution provide for a multitude of innate social behaviors that can be experimentally dissected. These fine‐tuned patterns of behavior are especially interesting when observing group decision making in the panic mode. In this study, we examined behavioral patterns of termites under panic conditions to gain insight into how an escape flow self‐organizes. One hundred worker and 10 soldier Coptotermes formosanus were released into agar plates. After a disturbance was created most workers followed each other and ran along the wall of dishes, thus forming a unidirectional escape flow, whereas soldiers showed a significantly higher frequency of moving to the center of the arena or on periphery of the escape flow as compared to workers. Agonistic behavior was usually observed as soldiers moved to center or periphery. This is the first report on the behavioral repertoire of termites when panicked, with details on the behavioral polymorphism of workers and soldiers during an escape.     

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.     

Comparative study of incipient colony development in the Formosan subterranean termite, <Emphasis Type="Italic">Coptotermes formosanus</Emphasis> Shiraki (Isoptera,Rhinotermitidae)

Summary The Formosan subterranean termite, Coptotermes formosanus Shiraki is the most destructive, difficult to control and economically important species of termite in the southern United States. At present, no information is available on the genetic relatedness of primary Formosan subterranean termite reproductives that establish new colonies. Information on survivorship and fitness components of primary reproductives from different sibships (sibling or nonsibling) is helpful to our understanding of biological and ecological characteristics of different breeding generations in C. formosanus. The present study examined the effects of sibship and colony origin on growth and mortality of incipient colonies of C. formosanus. Seven stock colonies of C. formosanus were collected in 1996 through 1997 in New Orleans and Lake Charles, La, USA. A total of 338 incipient colonies of sibling pairs or nonsibling pairs of C. formosanus were set up. The study indicated that mate relatedness significantly affected mortality and fitness. Nonsibling mates suffered significantly higher mortality than sibling mates originated from New Orleans. However, the decreased success of outbred mates was offset by an increased fecundity compared to inbred colonies over time. Both sibling- and nonsibling-founded colonies from Lake Charles had a significantly higher survival rate than did colonies from New Orleans. Colonies from Lake Charles also produced a significantly higher number of larvae/workers than colonies from New Orleans. The mismatch of habits by mates from different locations and the potential for greater disease risks may be associated with higher mortality in outbred pairs. However, heterozygous offspring of outbred pairs probably have increased genetic variation, which provides greater adaptation potential, thus making the colony more robust in the face of environmental fluctuations.Received 11 March 2002; revised 26 February 2003; accepted 14 March 2003.     

两种散白蚁两性生殖与孤雌生殖胚胎发育比较研究

【目的】探究散白蚁两性生殖胚胎和兼性孤雌生殖胚胎各自的发育特点。【方法】以黑胸散白蚁Reticulitermes chinensis和尖唇散白蚁R.aculabialis各自的受精卵(雌雄配对所产的卵)和未受精卵(雌雌配对所产的卵)为研究对象,采用激光共聚焦显微镜观测两种散白蚁的受精卵和未受精卵的卵裂状态,数码显微系统拍照观察卵的外部形态变化。【结果】黑胸散白蚁蚁后所产的受精卵和未受精卵在巢中均能进行卵裂,但是未受精卵在24和48 h时的卵核数无显著性差异,而受精卵卵核数在24和48 h时有显著性差异;15 d时未受精卵的体积没有发生显著变化,而受精卵的体积显著性增大;15-20 d时未受精的蚁卵死亡,而受精卵正常发育。尖唇散白蚁受精卵和未受精卵在相同的时间段内卵核数没有显著性差异,48 h时的卵核数明显比24 h时多;第10天时受精卵长度和宽度发生显著性变化,同时体积也明显增大,而未受精卵在第15天时长度和宽度才开始发生显著性变化,同时体积也开始显著增大。【结论】具有兼性孤雌生殖能力的尖唇散白蚁,受精卵和未受精卵卵裂速度相同,但受精卵外形体积变化比未受精卵早。黑胸散白蚁未受精卵能继续进行卵裂,但发育异常,不能孵化;两种白蚁卵发育过程中卵的长度和宽度同时发生变化。黑胸散白蚁孤雌卵的卵裂特性可能是白蚁两性生殖向兼性孤雌生殖进化的过渡适应阶段。     

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.     

Isolation and characterization of 10 microsatellite loci in the magnetic termite,Amitermes meridionalis (Isoptera: Termitidae)

The elongated mounds of the ‘magnetic termite’, Amitermes meridionalis are a prominent feature of the Northern Territory in Australia. They are restricted to habitat patches of seasonally flooded plains which are largely isolated from each other. To investigate the population structure of A. meridionalis, we developed 10 polymorphic microsatellite loci. We tested the variability of the markers on at least 20 individuals from two populations. We found three to 12 alleles per locus with a level of heterozygosity at each locus ranging from 0.05 to 0.74.     

Microsatellite markers in soil‐feeding termites (Cubitermes subarquatus,Isoptera, Termitidae,Termitinae)

Seven microsatellite markers were isolated from Cubitermes subarquatus belonging to the soil‐feeding termite trophic group that plays a key role in tropical rain forests. A variability study performed by using a population of C. subarquatus (n = 73) sampled in the La Lopé forest reserve (Gabon) from 42 nests revealed from 4 to 12 alleles per locus and an heterozygosity from 0.28 to 0.84. Tests for cross‐species amplification realized in the sympatric C. intercalatus and in eight other sympatric termite genera indicated a wider application of the primers isolated from Cubitermes in soil‐feeding termites.