The Effect of Queen and Worker Adoption on Weaver Ant (Oecophylla smaragdina F.) Queen Fecundity

Incipient ant colonies are often under fierce competition, making fast growth crucial for survival. To increase production, colonies can adopt multiple queens (pleometrosis), fuse with other colonies or rob brood from neighboring colonies. However, different adoption strategies might have different impacts such as future queen fecundity or future colony size. O. smaragdina queen production was measured in incipient colonies with 2, 3 or 4 founding queens, following the transplantation of 0, 30 or 60 pupae from a donor colony. Pupae developed into mature workers, resulting in increased worker/queen ratios in pupae transplanted treatments and leading to increases in the per capita queen production. Conversely, more queens did not induce increased per capita fecundity. Thus, brood robbing added individuals to the worker force and increased future production of resident queens, whereas queen adoption increased the colony’s future production, but not the production of individual queens.     

Landscape mulches and termite nutritional ecology: growth and survival of incipient colonies of Coptotermes formosanus (Isoptera: Rhinotermitidae)

Alate swarms are one of the major visible signs of the expansion of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), in an area. Successful establishment of an incipient colony is thought to mainly rely on available food resources and moisture. The large-scale use of tree-based mulches in landscapes may inadvertently contribute to local establishment and growth of C. formosanus colonies. This research investigated the nutritional ecology of incipient colonies of C. formosanus feeding on seven tree-based, weathered, and nonweathered landscape mulches: pine straw, pine bark, cedar wood, water oak, eucalyptus, cypress, and melaleuca. Incipient colonies of C. formosanus feeding on pine straw, either weathered or nonweathered, produced significantly more progeny over the course of 1-yr feeding than colonies feeding on the other mulches tested. Regardless of weathered or not, the incipient colonies feeding on pine straw, eucalyptus, bald cypress, and water oak mulches had significantly greater survival rates after 360 d (53-77%) than colonies feeding on the other mulches tested (0-13%), but colonies feeding on nonweathered water oak had significantly lower survival (8%) than those kept on weathered water oak (58%). Colony fitness values were significantly different between the weathering treatment groups and among the different types of mulches. With regard to colony growth characteristics, three distinct growth patterns were identified: a high number of progeny (>100) with high colony survival rate (>50%), a medium number of progeny (12-50) with high colony survival rate (>50%), and a small number of progeny (0-10) with low colony survival rate (<5%). These findings suggest that different types of mulch substrates could significantly impact the nutritional ecology of the founding pairs and the successful establishment of incipient colonies during the swarming season.     

Nutritional ecology of the Formosan subterranean termite (Isoptera: Rhinotermitidae): growth and survival of incipient colonies feeding on preferred wood species

The wood of 11 plant species was evaluated as a food source significantly impacting the growth and survival of incipient colonies of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae). Colonies of C. formosanus feeding on pecan, Carya illinoensis (Wangenh.), and red gum, Liquidambar styraciflua L., produced significantly more progeny than colonies feeding on other wood species tested. Progeny of colonies feeding on pecan and American ash, Fraxinus americana L., had significantly greater survival than progeny of colonies feeding on other wood species. Colonies feeding on a nutritionally supplemented cellulose based matrix showed similar fitness characteristics as colonies feeding on the best wood treatments. These results indicate that differences observed in colony fitness can be partially explained by nutritional value of the food treatment, raising the possibility that wood from different tree species have different nutritional values to the Formosan subterranean termites. Colonies feeding on loblolly pine, Pinus taeda L., and ponderosa pine, Pinus ponderosa Laws., had significantly lower survival and produced significantly fewer workers and soldiers than colonies feeding on other wood species. Colony survival from 90 to 180 d of age and from 90 to 360 d of age was significantly correlated with the number of workers present at 90 d of colony age, indicating that colony survival depends on the presence of workers. Wood consumption in a multiple-choice study was significantly correlated with colony fitness value. This suggests that feeding preference of C. formosanus is at least partially influenced by the nutritional value of the food source.     

Spatial patterns, temporal variability, and the role of multi-nest colonies in a monogynous Spanish desert ant

Abstract 1. The colonies of the Spanish desert ant Cataglyphis iberica are polydomous. This study describes the temporal and spatial patterns of the polydomy in this species at two different sites, and presents analyses of its role in reducing the attacks of the queen over sexual brood, and in allowing better habitat exploitation.
2. The spatial distribution of nests was clumped while colonies were distributed randomly. Mean nearest neighbour distance ranged from 3.4 to 7.0 m for nests and from 12.3 to 14.1 m for colonies. Distance of foragers searching for food varied among nests: mean values were between 6.1 and 12.6 m.
3. At both sites, the maximum number of nests per colony occurred in summer, during the maximum activity period of the species. Colonies regrouped at the end of this period but overwintered in several nests.
4. Nest renewal in C. iberica colonies was high and showed great temporal variability: nests changed (open, close, re-open) continuously through the activity season and/or among years. The lifetime of up to 55% of nests was only 1–3 months.
5. Polydomy in C. iberica might decrease the interactions between the queen and the sexual brood. In all colonies excavated just before the mating period, the nest containing the queen did not contain any virgin female. Females were in the queenless nests of the colony.
6. The results also suggest that polydomous C. iberica colonies may enhance habitat exploitation because foraging activity per colony increases with nest number. The relationship between total prey input and foraging efficiency and number of nests per colony attains a plateau or even decreases after a certain colony size (four to six nests). This value agrees with the observed mean number of nests per colony in C. iberica .     

Elimination and reinvasion studies with Coptotermes formosanus (Isoptera: Rhinotermitidae) in Louisiana

Three Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), colonies located inside the 12.75-ha Louis Armstrong Park, New Orleans, were selected for elimination by using the chitin synthesis inhibitor hexaflumuron. Once eliminated, each vacated foraging territory was monitored for reinvasion by neighboring C. formosanus colonies, Reticulitermnes flavipes (Kollar) (Isoptera: Rhinotermitidae) colonies, or both. Each selected colony was eliminated in approximately 3 mo by using baits containing hexaflumuron. Overall activity of each untreated colony in the park remained unchanged during the same period. New C. formosanus and R. flavipes activity was detected in two of the three vacated territories, and in both areas, within days of selected colony elimination. The third vacated territory was completely reoccupied by a new C. formosanus colony approximately 7 mo later. Mark-recapture studies and DNA fingerprinting confirmed the distinctness of the reinvaders from eliminated and neighboring colonies.     

家白蚁群体数增长的生殖生理特点

家白蚁Coptotermes formosanus Shiraki营大巢生活,由于雌虫生殖潜能很大,群体蚁数极多.群体蚁数的逐年增长和雌蚁卵巢内卵巢管的数目增长有密切关系.实验表明,分飞时的雌虫卵巢有8条卵巢管,初建群体,半年内一群体的蚁数仅为57个.经过四年后发育的群体,蚁数是1,767个,这时的蚁后卵巢管数是75条.二年群体的年幼蚁后腹部稍膨大,三年以上的群体,蚁后的1腹部膨大较显著.一年的群体,雌虫体长是0.78厘米,雄虫体长0.71厘米.九年后的群体,蚁后体长是2.1厘米,蚁王体长为1.2厘米.和卵巢相似,雄虫精巢叶的数目也随时间而增加.     

Cuticular permeability of two species of Coptotermes Wasmann (Isoptera: Rhinotermitidae)

Cuticular permeability (CP) values of worker and soldier castes of Coptotermes formosanus Shiraki and Coptotermes vastator Light were determined using gravimetric techniques. Comparisons were made between castes, species, and between colonies of C. formosanus and C. vastator. CP values did not differ among either species or colony, however they did differ between castes. Data reported here and that of established data in the literature for C. formosanus are inconsistent, with the current report having values as small as half that of previously published data. Examining mean CP data by colony indicated that there is a range for Coptotermes spp. termites, from 6.84+/-1.2 to 25.61+/-1.49 microg H(2)Ocm(-2)mmHg(-1)h(-1) dependent upon caste. A novel method of examining intercaste CP variability is the use of worker:soldier CP ratios. Ratios for C. formosanus were consistent between the current study and previous reports. Mean percentage total body water (%TBW) lost at the time of death was 33.75+/-1.15% (soldiers) and 54.24+/-1.43% (workers) for C. formosanus, and 37.69+/-3.31% (soldiers) and 52.87+/-3.65% (workers) for C. vastator. Consistently, %TBW (and fresh mass) was greater in worker than in soldier castes. These data suggest the use of water storage mechanisms in worker termites, as shown for other rhinotermitids.     

On the relationship between queen number and fecundity in polygyne colonies of the fire ant Solenopsis invicta

ABSTRACT. The reproductive status of individual queens in relation to the number of queens in polygyne colonies of Solenopsis invicta Buren was investigated under both field and laboratory conditions. In field colonies, the weight of individual queens is inversely related to the number of resident queens present. The weight of a queen is positively correlated with fecundity, as measured by the number of eggs laid in 5 h in isolation. Thus increasing queen number has a strong negative effect on the fecundity of individual queens in these colonies. A similar relationship was established in standardized laboratory colonies using queens from a single experimental population. Colony size by itself had no significant effect on queen weight in either the field or laboratory colonies, suggesting that the inverse relationship between queen number and fecundity results from mutual inhibition among queens, possibly involving pheromones, rather than reduced nutrition through lower worker/queen ratios. While uninseminated queens can comprise up to 50% of the functional (i.e. egglaying) queens in polygyne colonies of this ant, they tend to be less fecund than their inseminated nestmates; uninseminated queens within a given colony generally weigh 5–25% less.     

Colony dynamics of the Formosan subterranean termite in a frequently disturbed urban landscape

The success of evaluating areawide control of the Formosan subterranean termite, Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae), in urban landscapes hinges on detailed understanding of colony movement and plasticity of the breeding system. Most previous studies of colony affiliation and breeding systems of C. formosanus have been conducted in relatively undisturbed park-like areas. However, disturbance in the form of landscaping, construction, and nearby treatment may impact termite colony dynamics in urban habitats. Therefore, we used microsatellite genotyping to identify the number of colonies, assess colony movement, and investigate the breeding structure of colonies surrounding the Supreme Court Building in New Orleans, LA. During 4 yr, 18 distinct colonies were identified in the study area. In contrast to earlier studies in park-like areas, which indicated stable foraging areas, colonies in this study moved frequently into and out of inground stations. Five colonies were simple families; two of these colonies were headed by inbred nestmate pairs, and three of these colonies were headed by outbred unrelated pairs. Thirteen colonies were extended families headed by fewer than five neotenic reproductives. During the study, the predominant breeding system shifted; simple family colonies either moved or were eliminated, and they were replaced with new extended family colonies. In one case, a generation turnover within a colony from simple to extended family was observed.     

Polyandry and fitness in the western harvester ant, Pogonomyrmex occidentalis

Using four highly polymorphic microsatellite markers (12-28 alleles), we gentoyped workers from 63 colonies of Pogonomyrmex occidentalis. Colonies have a single, multiply mated queen, and an average number of 6.3 patrilines per colony. Colony growth was measured over an 8-year period in the study population. Intracolonial relatedness and colony growth are correlated negatively, indicating a substantial fitness benefit to multiple mating.     

Benefits and costs of secondary polygyny in the dampwood termite Zootermopsis angusticollis

Newly molted female neotenic reproductives of the dampwood termite Zootermopsis angusticollis Hagen were allowed to mature in the presence of a neotenic male, a fixed number of larval helpers, and varying numbers of sibling neotenic queens to assess the impact of secondary polygyny to the individual and colony. Under monogyne conditions, neotenics developed more ovarioles per ovary and had higher individual fecundities after 60 d compared with females under polygyne conditions. Queens in groups of three females were able to gain more body mass than those in groups of five. Although the division of resources provided by helpers reduced individual female development and fecundity under polygyne conditions, it resulted in an overall increase in colony fecundity. In addition, neotenic females in polygynous colonies did not differ significantly in reproductive competence. There was no evidence that neotenics were attacked or injured by other reproductives or larval helpers, suggesting little if any reproductive competition among sibling queens. The physiological responses of neotenics to the increasing queen/worker ratio may have the benefit of enhancing the colony growth at the cost of the fecundity of individual queens.     

Development rate and brood production in haplo- and pleometrotic colonies of <Emphasis Type="Italic">Oecophylla smaragdina</Emphasis>

Pleometrosis (colony founding by multiple queens) may improve life history characteristics that are important for early colony survival. When queens unite their initial brood, the number of workers present when incipient colonies open may be higher than for single queen colonies. Further, the time until the first worker emerges may shorten. For territorial species and species that rob brood from neighbouring colonies, a faster production of more workers may improve the chance of surviving intraspecific competition. In this study, the time from the nuptial flight to the emergence of the first worker in incipient Oecophylla smaragdina Fabr. colonies founded by 1–5 queens was compared and the production of brood during the first 68 days after the nuptial flight was assessed. Compared to haplometrotic colonies, pleometrotic colonies produced 3.2 times more workers, their first worker emerged on average 4.3 days (8%) earlier and the queen’s per capita egg production almost doubled. Further, colony production was positively, correlated with the number of founding queens and time to worker emergence was negatively correlated. These results indicate that pleometrotic O. smaragdina colo-nies are competitively superior to haplometrotic colonies as they produce more workers faster and shorten the claustral phase, leading to increased queen fecundity.     

Disruption of reproductive activity of Coptotermes formosanus (Isoptera: Rhinotermitidae) primary reproductives by three chitin synthesis inhibitors

Effects of the chitin synthesis inhibitors (CSIs) diflubenzuron, hexaflumuron, and lufenuron on the Formosan subterranean termite, Coptotermes formosanus Shiraki, primary reproductives were studied in the laboratory. Incipient colonies were established by collecting and pairing C. formosanus alates and placing them in dishes containing an artificial diet. Three groups of 56 colonies each were fed with a diet containing 10 ppm of one of each of the CSIs and were compared with a control group fed with an untreated diet. All eggs oviposited by treated young queens failed to hatch at the end of 6 mo. Estimated queen fecundity was significantly lower in the lufenuron treatment compared with the control group. Fecundity of hexaflumuron-treated queens did not differ significantly from that of queens from the control group and the other treatments. Adult mortality was significantly higher in the diflubenzuron and lufenuron treatments than in the control group at the end of 6 mo., but not in the hexaflumuron treatment. All the pairs died within 8 mo. in the diflubenzuron and lufenuron treatments, even after treatment was suspended at the end of 6 mo. Mortality in the hexaflumuron treatment was significantly higher than in the control group by the end of 9 mo. The three CSIs tested eliminated reproduction in C. formosanus by preventing egg hatching and induced adult mortality. Possible mechanisms by which CSIs induce termite adult death are discussed.     

Social control of egg-laying rate in queens of the fire ant, Solenopsis invicta*

ABSTRACT Social control of egg-laying rate in queens of the fire ant (Solenopsis invicta Buren) was studied by experimental manipulation of the number of larvae, pupae and workers in colonies, and the age and size of larvae and workers. Workers and pupae do not stimulate oviposition by queens. The number of fourth instar larvae, on the other hand, bears a positive log-log relationship to the queen's egg-laying rate. Such larvae are needed both to stimulate and maintain oviposition. Their withdrawal results, within 48 h, in a decline in queen oviposition almost to zero. Their addition to broodless nests results in peak laying in about 4 days. Larvae in the first three stadia and early in the fourth stadium have a much lower effect upon queen fecundity. Sexual larvae are only c. 5% as stimulating on a weight basis, but equivalent on an individual basis. Several associated measures are positively correlated to egg-laying rate: weight of the queen, the number of her vitellogenic follicles per ovariole, total vitellogenic follicles, the time she spends feeding and (usually) the number of workers in the retinue that cares for her. The egg volume is negatively correlated with laying rate, so that queens lay more eggs for the same expenditure of material as laying rate increases. As body size of workers increases, they become less effective in transmitting the larval stimulation to the queen, but worker age has no effect on this ability. For a given number of larvae, queens in small, naturally growing colonies lay fewer, larger eggs than do queens in experimental colonies, but their fecundity increases more rapidly in relation to number of larvae. When larvae are fed vital-dyed food in one experimental colony, and then transferred to an undyed colony, the dye is rapidly transferred to worker crops, and into the queen's eggs, indicating bulk movement of material from larvae to workers to the queen and eggs. Large larvae are more effective at this than small larvae. Fourth instar larvae may be a digestive and metabolic caste that processes protein for egg production by the queen. If that is the case, the queen and fourth instar larvae are linked in a positive feedback loop. Either the logarithmic relation of fecundity to larval numbers or physical limits of the queen may set the maximum egg-laying rate, and thus determine maximum colony size. The data do not allow a clear choice between these alternatives.     

Fitness and the level of homozygosity in a social insect

To date very few studies have addressed the effects of inbreeding in social Hymenoptera, perhaps because the costs of inbreeding are generally considered marginal owing to male haploidy whereby recessive deleterious alleles are strongly exposed to selection in males. Here, we present one of the first studies on the effects of queen and worker homozygosity on colony performance. In a wild population of the ant Formica exsecta, the relative investment of single‐queen colonies in sexual production decreased with increased worker homozygosity. This may either stem from increased homozygosity decreasing the likelihood of diploid brood to develop into queens or a lower efficiency of more homozygous workers at feeding larvae and thus a lower proportion of the female brood developing into queens. There was also a significant negative association between colony age and the level of queen but not worker homozygosity. This association may stem from inbreeding affecting queen lifespan and/or their fecundity, and thus colony survival. However, there was no association between queen homozygosity and colony size, suggesting that inbreeding affects colony survival as a result of inbred queens having a shorter lifespan rather than a lower fecundity. Finally, there was no significant association between either worker or queen homozygosity and the probability of successful colony founding, colony size and colony productivity, the three other traits studied. Overall, these results indicate that inbreeding depression may have important effects on colony fitness by affecting both the parental (queen) and offspring (worker) generations cohabiting within an ant colony.     

Seasonal patterns of egg production in field colonies of the termite <Emphasis Type="Italic">Reticulitermes speratus</Emphasis> (Isoptera: Rhinotermitidae)

This is the first report on the annual egg production patterns in mature termite colonies in the field. Data on the seasonal patterns of egg production in field colonies are very important for understanding the annual colony growth schedule, resource allocation, and population dynamics of the termites. However, collecting the eggs from a sufficient number of colonies is extremely difficult in Reticulitermes termites because their multiple-site nesting makes it difficult to find the reproductive center of the colonies. Here, we first show the seasonal pattern of egg production in the subterranean termite Reticulitermes speratus by collecting the reproductive center of ten colonies each month from April through October. We had to destructively examine dozens of nests to find eggs from enough field colonies each month. Mature field colonies began to produce eggs in late May, soon after the swarming season, and the egg production rate (EPR) reached its maximum in early July. The eggs hatched until late October. The EPR was significantly correlated with the average monthly temperature. Additional investigation of the egg distributions in the nests showed that most eggs were kept around the royal cell, which contained the reproductives. The largest colony had 109 supplemental queens and 94,023 eggs, suggesting that each queen produced an average of 24.7 eggs per day, based on the known mean hatching period of an inseminated egg of 34.95±0.12 (SE) days.     

Delayed maturation in the colonial coralGoniastrea aspera (Scleractinia): whole-colony mortality, colony growth and polyp egg production

The present study examines (1) the cost of reproduction on colony growth, and (2) relationships among sexual maturity, whole-colony mortality rate and colony growth rate inGoniastrea aspera free from external influences by macrobenthos. Survival of colonies in permanent plots was followed for two years. Egg production by polyps in colonies collected just before the first spawning of a year was estimated by dissecting the polyps. Growth of the colonies (increase in number of polyps) was followed over one annual reproductive cycle. The cost of egg production on colony growth was apparent through colony ontogeny: (1) immature colonies had a greater annual growth rate than mature colonies, but produced almost no eggs; (2) in mature colonies, growth rate was negatively correlated with NE/PV (number of eggs per polyp volume mm^-3). Annual whole-colony mortality was high in colonies with fewer than11 polyps in initial colony size, while mortality was extremely low once a colony grew beyond this size. This critical size for low whole-colony mortality was much smaller than the colony size (40 polyps) which would attain maturity one year later. Age at maturity was estimated as six years. While survival to maturity may be a selective force for the evolution of delayed maturation, the present data suggest that high colony fecundity, achieved after a long growth period as an immature colony, and an abrupt decrease of colony growth rate after maturation are the crucial forces.     

Queen recruitment and split sex ratios in polygynous colonies of the ant Formica exsecta

Sex ratios in social insects have become a general model for tests of inclusive fitness theory, sex ratio theory and parent–offspring conflict. In populations of Formica exsecta with multiple queens per colony , sex ratios vary greatly among colonies and the dry-weight sex ratio is extremely male-biased, with 89% of the colonies producing males but no gynes (reproductive females). Here we test the queen-replenishment hypothesis, which was proposed to explain sex ratio specialization in this and other highly polygynous ants (i.e. those with many queens per nest). This hypothesis proposes that, in such ants, colonies produce gynes to recruit them back into the colony when the number of resident queens falls below a given threshold limiting colony productivity or survival. We tested predictions of the queen-replenishment hypothesis by following F. exsecta colonies across two breeding seasons and relating the change in effective queen number with changes in sex ratio, colony size and brood production. As predicted by the queen-replenishment hypothesis, we found that colonies that specialized in producing females increased their effective queen number and were significantly more likely to specialize in male production the following year. The switch to male production also coincided with a drop in productivity per queen as predicted. However, adoption of new queens did not result in a significant increase in total colony productivity the following year. We suggest that this is because queen production comes at the expense of worker production and thus queen production leads to resource limitation the following year, buffering the effect of greater queen number on total productivity.     

Reproductive allocation within a polygyne, polydomous colony of the ant Myrmica rubra

1. Ant colonies commonly have multiple egg‐laying queens (secondary polygyny). Polygyny is frequently associated with polydomy (single colonies occupy multiple nest sites) and restricted dispersal of females. The production dynamics and reproductive allocation patterns within a population comprising one polygyne, polydomous colony of the red ant Myrmica rubra were studied. 2. Queen number per nest increased with nest density and the number of adult workers increased with the number of resident queens and with nest density. This suggests that nest site limitation promotes polygyny and that workers accumulate in nest units incapable of budding. 3. Nest productivity increased with the number of adult workers and production per queen was independent of queen number. Productivity increased with nest density, suggesting local resource enhancement. This shows that productivity can be a linear function of queen numbers and that the limiting factor is not the egg‐laying capacity of queens. 4. The total and per capita production of reproductives decreased towards the periphery of the colony, suggesting that the spatial location of nest units affects sexual production. Thus nests at the periphery of the colony invested more heavily in new workers. This is consistent with earlier observations in plants and could either represent investment in future budding or increased defence. 5. The colony produced only five new queens and 2071 males, hence the sex ratio was extremely male biased.     

Insecticide susceptibility in Coptotermes formosanus and Reticulitermes virginicus (Isoptera: Rhinotermitidae).

Lethal time to mortality responses were established for eight insecticides against workers and soldiers of the Formosan subterranean termite, Coptotermes formosanus Shiraki, and workers of Reticulitermes virginicus (Banks). There were significant differences in the tolerance ratios between workers of C. formosanus colonies to all toxicants tested except fipronil. One colony was 16 times more tolerant than another to deltamethin. C. formosanus soldiers had significant differences in tolerance ratios among colonies exposed to all toxicants except chlorpyrifos. Methoxychlor, permethrin, deltamethrin, and fipronil did not kill soldiers from two, one, one, and three colonies, respectively, within 8 h. Seventy-five percent of R. virginicus colonies were significantly less susceptible than the most susceptible colony to chlordane, methoxychlor, chlorpyrifos, cypermethrin, and fipronil, with 50% of the colonies less susceptible to permethrin and bendiocarb. In 50% of C. formosanus colonies the worker lethal time curves displayed substantial flattening in response to permethrin, and deltamethrin. Lethal time curses for C. formosanus soldiers exposed to chlordane, chlorpyrifos, permethrin, cypermethrin, deltamethrin, and bendiocarb showed substantial flattening. R. virginicus workers demonstrated substantial curve flattening when exposed to chlordane, methoxychlor, chlorpyrifos, deltamethrin, and fipronil. These findings indicate substantial intercolony and intra-colony differences in susceptibility to insecticides.