Ergatoid reproductives in Nasutitermes columbicus (Isoptera,Termitidae)

Numerous functional ergatoid replacement reproductives were found in one colony of Nasutitermes columbicus in Panama. Their morphology was mainly workerlike, although several imaginal characters such as the compound eyes and variable wing buds were more or less developed. The sex organs were fully mature and the fat body of the females, not of the males, was of the “royal” type. The development of the eyes was not accompanied by the differentiation of the optic lobes of the brain, nor was the presence of wing buds correlated with a development of the wing muscles.     

Characterization of Nasutitermes globiceps (Isoptera: Termitidae) Esterases

Esterases of Nasutitermes globiceps termites which occur on the Upper Paraná River floodplain (Brazil) were characterized. The electrophoretic pattern of the termite esterases Nasutitermes globiceps was obtained by starch gel electrophoresis. Six esterase activity zones were obtained and numbered, with esterase-1 being the most anodall one and esterase-6 the most cathodal one. Esterase-2 was detected only with substrates derived from the 4-methylumbelliferyl radical. The esterases of N. globiceps present wide substrate specificity, having been observed with substrates derived from alpha-naphthyl (acetate, propionate, and butyrate) and beta-naphthyl (acetate, butyrate) and from 4-methylumbelliferyl (acetate, propionate and butyrate). Esterase-6 is a caste-specific enzyme detected in soldiers. Only esterases 1, 3 and 5 were detected in nymphs. No genetic polymorphism has been detected thus far in the esterases of Nasutitermes globiceps. This study suggests that allozyme variation can be explored to understand Nasutitermes social structure.     

Growth and demography ofCubitermes speciosus mounds (Isoptera,Termitidae)

The growth and demography ofCubitermes speciosus mounds were studied in an equatorial forest ecosystem near Kisangani, Zaïre. The mounds were censused and measured on eight occasions from June 1985 to January 1993 on 25 plots of 100 m².Mounds were found to grow in two ways: either they were enlarged sporadically, leading to a correlation between age and size; or they were no longer enlarged after a 2-year period of initial growth, which means that both large and small mounds can be old.The number of living mounds was fairly constant: it varied between 112 and 152 ha^–1 with an average of 139 ha^–1, and about a quarter of them were renewed each year. However, a clear tendency was observed over our 7.5-year observation period: the average size of the mounds increased regularly and was 2.7 times larger in 1993 than in 1985.Monthly birth and death rates were estimated using a model of continuous growth. Life expectancy at the age of 3 months was estimated from a survivorship curve at 3.5 years.     

Forces affecting water imbibition inMacrotermes workers (Termitidae,Isoptera)

Summary Observations of putative drinking behaviour at soil surfaces by major workers ofMacrotermes subhyalinus andM. bellicosus suggested that unidirectionally arranged trichomes on the anterior hypopharynx exert capillarity on water in soil pores. To test this hypothesis thirsty major workers were placed on soil of relatively low water content. From the soil types tested we determined soil-moisture retention curves which represent graphically the water content of the soil and its corresponding capillary potential. The termites were able to obtain water from different types of clay soil against potentials in the range – 1.6 to – 1.9 bar. On sandy soil the capillary potential was found to be much higher (– 0.18 bar), i.e. closer to zero. Sandy soil has a very unfavourable water retention capacity, i.e. its water content is very low at low capillary potential, whereas clay soil retains much more water at low capillary potential. The ability of the termites to gain water from soils with relatively low water content is an important adaptive feature for survival in semi-arid areas.     

Divergence times in the termite genus Macrotermes (Isoptera: Termitidae)

The evolution of fungus-growing termites is supposed to have started in the African rain forests with multiple invasions of semi-arid habitats as well as multiple invasions of the Oriental region. We used sequences of the mitochondrial COII gene and Bayesian dating to investigate the time frame of the evolution of Macrotermes, an important genus of fungus-growing termites. We found that the genus Macrotermes consists of at least 6 distantly related clades. Furthermore, the COII sequences suggested some cryptic diversity within the analysed African Macrotermes species. The dates calculated with the COII data using a fossilized termite mound to calibrate the clock were in good agreement with dates calculated with COI sequences using the split between Locusta and Chortippus as calibration point which supports the consistency of the calibration points. The clades from the Oriental region dated back to the early Tertiary. These estimates of divergence times suggested that Macrotermes invaded Asia during periods with humid climates. For Africa, many speciation events predated the Pleistocene and fall in range of 6-23 million years ago. These estimates suggest that savannah-adapted African clades radiated with the spread of the semi-arid ecosystems during the Miocene. Apparently, events during the Pleistocene were of little importance for speciation within the genus Macrotermes. However, further investigations are necessary to increase the number of taxa for phylogenetic analysis.     

Queen-specific volatile in a higher termite Nasutitermes takasagoensis (Isoptera: Termitidae)

In social insect colonies, queen-produced pheromones have important functions in social regulation. These substances influence the behavior and physiology of colony members. A queen-produced volatile that inhibits differentiation of new neotenic reproductives was recently identified in the lower termite Reticulitermes speratus. However, there are no known queen-specific volatiles of this type in any other termite species. Here, we report volatile compounds emitted by live queens of the higher termite Nasutitermes takasagoensis. We used headspace gas chromatography mass spectroscopy (HS GC-MS) to analyze volatiles emitted by live primary queens, workers, soldiers, alates, and eggs collected in a Japanese subtropical forest. Among 14 detected compounds, 7 were soldier-specific, 1 was alate-specific, 1 was egg-specific, and 1 was queen-specific. The queen-specific volatile was phenylethanol, which is different than the compound identified in R. speratus. The identification of this queen-specific volatile is the first step in determining its functions in higher termite social regulation. Comparisons of queen pheromone substances regulating caste differentiation among various termite taxa will contribute to a better understanding of the evolution of social systems in termites.     

On the elevated intestinal pH of higher termites (Isoptera: Termitidae)

Summary The pH of the gut contents was measured in 52 species of higher termites (Termitidae), representing 36 genera in all four subfamilies. A statistically significant trend was shown from lower termites with low mean gut pH through to the Termitinae with higher mean gut pHs. Elevation of the pH occurred principally in the first and third proctodaeal segments, reaching values as high as 10.5 in 8 soil-feeding genera and 1 wood-feeding genus of Termitinae. Elevation of gut pH within the Termitidae appears to be independent of the general nature of the feeding substrate.     

Open-Air Litter Foraging in the Nasute Termite Longipeditermes longipes (Isoptera: Termitidae)

The Southeast Asian nasute termite Longipeditermes longipes forages on the open ground on leaf litter. Its monomorphic workers carry back food balls in their mandibles while dimorphic soldiers defensively surround the marching columns and the foraging patches. When mechanically disturbed, workers hide under the litter, whereas antennating soldiers face as closely as possible the source of disturbance. Foragers prefer the lower, nitrogen-rich layer of the litter. Soldier behavior and column organization (returning workers in the center lanes, outgoing workers in the two flanking lanes) are similar to those in the related genera Hospitalitermes and Lacessititermes, which, however, tend to forage above ground.     

Intraspecific interactions in a community of arboreal nesting termites (Isoptera: Termitidae)

In coconut plantations of northern New Guinea, the arboreal nesting termite community comprises three species:Nasutitermes princeps, N. novarumhebridarum, andMicrocerotermes biroi. In orde to assess the importance of intraspecific interactions in this community, we conducted pairwise encounters between batches of individuals in the laboratory and between entire nest populations in seminantural conditions. Three levels of agonism were defined in laboratory bioassays: anagonism, moderate agonism, and strong agonism. Anagonism was observed during all control tests with homocolonical groups and in some tests with allocolonial groups of all species. Moderate agonism included initial aggressiveness that subsequently faded out, and initially passive encounters where aggression progressively built up and led to fighting. Strong agonism corresponded to initial aggressiveness and fighting. Results obtained in alboratory bioassays were consistent with bioassays in seminatural conditions. WhenNasutitermes colonies were anagonists in laboratory bioassays, their foraging trails merged without aggression in field tests.N. princeps nests that were moderately agonistic in laboratory tests fought and either continued to avoid each other or finally joined after elimination of the most aggressive individuals. The most aggressiveM. biroi andN. princeps colonies fought and their foraging trails diverged afterward. Direct attacks on alien nests were winnessed inM. biroi. In all species, anagonism occurred in 21–34% of the combinations tested, between either geographically close or distantcolonies. An exeption was a group of 112 anagonist nests ofN. princeps, which most probably constituted a supercolony. The level of agonism betweenNasutitermes colonies was constant during the wet and dry season. Termite colonies excluded each other, both intra- and interspecifically, from the coconut trees, and their territories seem distributed in a mosaic pattern. Agonism between colonies may result in the elimination of the weakest colonies or in trail divergence, maintaining this mosaic. In cotrast, lack of agonism between some colonies suggests the possibility of colony fusion and gene exchanges without nuptial flights.     

High gene flow between populations of Macrotermes michaelseni (Isoptera, Termitidae)

Termite alates are thought to be poor active flyers, and this should lead to considerable genetic differentiation on small spatial scales. However, using four microsatellite loci for the termite Macrotermes michaelseni we found low values of genetic differentiation (F_ST) across a spatial scale of even more than 50 km. Genetic differentiation between populations increased with spatial distance up to 50 km. Furthermore, up to this distance, the scatter around the linear regression of genetic differentiation versus spatial distance increased with spatial distance. This suggests that across such spatial distances gene flow and genetic drift are of about equal importance, and near equilibrium. Using a regional F_ST as well as the distance between populations with non-significant F_ST-values (up to 25 km), gene flow is sufficiently high so that populations may be regarded as panmictic on spatial scales of 25 to 50 km. The apparent contradiction between dispersal distances observed in the field and estimates of gene flow from genetic markers may be due to the masses of swarming alates. Assuming a leptokurtic distribution of dispersal distances, atleast some alates are expected to travel considerable distances, most likely by passive drift. Received 25 January 2005; revised 11 April 2005; accepted 26 April 2005.     

Fine Structure of the Labial Gland in Macrotermes bellicosus (Isoptera,Termitidae)

The labial gland in M. bellicosus corresponds with the acinar type, and occupies the greater part of meso- and metathorax. The acini comprise three secretory cell types, in addition to the central ductule cells and the epithelial cells that make up the efferent ducts. Cell types are mainly distinguished by the size and appearance of their secretory vesicles and the extent of the microvillar contact area with the ductule cells. They probably produce a proteinaceous secretion that may contain digestive enzymes. The labial gland acini in soldiers, on the other hand, contain only one type of secretory cell, which is not comparable with any of the cell types in the worker caste. This difference is in agreement with the multifunctional role of the labial gland according to the termites' polyethism.     

Redescription of the enigmatic genus Genuotermes Emerson (Isoptera,Termitidae, Termitinae)

The imago and soldier castes of the Neotropical Termitinae species Genuotermes spinifer Emerson are redescribed. The gut anatomy of the worker is described in detail for the first time, and morphological variations in the soldier are noted and illustrated. The known geographical distribution of Genuotermes spinifer is greatly expanded.     

Daily and seasonal patterns of construction activity byOdontotermes latericius (Isoptera: Termitidae)

Summary Colonies ofOdontotermes ?latericius in the vicinity of Lusaka, Zambia, built their mounds primarily during the rainy season. Individual colonies began building some time before or after the beginning of the rains. Building usually ended before the end of the rains, but some colonies continued to build for some time after this. Occasionally a heavy rain after a period of dry weather caused numerous colonies to begin building again. There was no clear relation between building activity and other environmental factors.The pattern of activity within the rainy season varied greatly from colony to colony and year to year. Some colonies did no building during an entire season, and there was never a time when all colonies were active simultaneously. Except for a crude correlation of activity associated with rainfall the colonies seemed to be active at random with respect to each other. A colony sometimes remained continuously active for several months, but others were sometimes active for less than a day. A colony sometimes concentrated all its activity on one mound or chimney, but at other times activity shifted erratically from site to site. The structures built in one season usually were not used the following season. When building, the termites were active day and night, but usually were most active at night and least active on hot dry days.

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Résumé Dans les environs de Lusaka, Zambie, les colonies d'Odontotermes latericus construisent essentiellement leurs monticules durant la saison des pluies. Certaines colonies commencent la construction peu de temps avant ou après le commencement des pluies. En général, la construction cesse avant la fin des pluies mais quelques colonies continuent à construire pendant quelque temps après cette période. Habituellement une forte pluie après une période de sécheresse incide de nombreuses colonies à construire à nouveau.On ne trouve aucune relation évidente entre le comportement constructeur et d'autres facteurs d'environnement.Le schéma d'activité pendant la saison des pluies varie considérablement d'une colonie à l'autre et d'une année à l'autre. Certaines colonies ne construisent pas durant une saison entière et on n'observe jamais une période d'activité générale pour toutes les colonies. A part la corrélation évidente entre l'activité et les pluies, les colonies semblent actives au hasard chacune relativement aux autres. Une colonie peut rester active continuellement pendant plusieurs mois tandis que l'activité d'une autre peut durer moins d'un jour. Une colonie peut concentrer son activité sur une cheminée ou un monticule, tandis qu'à d'autres moments elle peut passer d'un emplacement à un autre de manière erratique. Les constructions édifiées durant une saison ne sont généralement pas utilisées durant la saison suivante. Pendant la construction, les termites sont actifs durant le jour et la nuit, mais habituellement ils sont les plus actifs durant la nuit et le moins pendant les jours chauds et secs.