Proportions Of Soldiers Research Articles

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

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

Influence of Soldiers on Exploratory Foraging Behavior in the Formosan Subterranean Termite, Coptotermes formosanus (Blattodea: Rhinotermitidae).

Termites are eusocial insects that live in organized colonies consisting of reproductives, workers, and soldiers. Soldiers are specialized for defense but are expensive to maintain, as they are incapable of husbandry and must be fed and groomed by workers. The soldiers of several species influence foraging behavior by acting as scouts that initiate foraging or by mediating worker behavioral plasticity during food exploration. These behaviors imply that soldiers may play a keystone role in termite colony function, apart from defense. Subterranean termite workers tunnel through soil in search of food while accompanied by varying proportions of soldiers, depending on the species and colony conditions. Previous studies have shown that soldiers accelerate worker exploratory tunneling behavior in two Reticulitermes species, the colonies of which contain fewer than 2% soldiers. This effect, however, is unknown in other subterranean species with different soldier proportions. In this study, we examined the influence of soldiers on exploratory foraging behavior in the Formosan subterranean termite, Coptotermes formosanus Shiraki, which is an economically devastating invasive species that maintains a relatively high soldier proportion (about 10%). When 100 foraging workers were grouped with 0, 2, 10, or 30 soldiers in two-dimensional foraging arenas, we found no significant effect of soldiers on the tunnel length, branch pattern, food source interception, or food collected within 96 h. These results suggest that C. formosanus colonies maintain food exploration efficiency regardless of soldier proportion variation.

A-231 Using Rates of Low Scores to Assess Agreement between CogState and a Traditional Battery of Neuropsychological Tests

Abstract Objective CogState is a brief computerized test battery used to assess cognitive function. We compare intra-individual agreement between CogState and a battery of traditional neuropsychological tests using rates of low scores. Methods Complete and valid data from 246 healthy soldiers and 177 soldiers ≤ 7 days from sustaining mild TBI (mTBI) were used in this analysis. All soldiers were consecutively administered CogState and a traditional test battery consisting of: TOPF, WAIS-IV, CVLT-II, RCFT, DKEFS, and CPT-II. We performed base rate analyses of both batteries to determine the proportions of soldiers who had various numbers of scores that were 1.0+, 1.5+, and 2.0+ standard deviations below the normative mean. We used those rates to place Soldiers into a “low score hierarchy” ranging from the least poor (i.e. ~ > 10th %ile) to the worst overall performance (i.e. ~ ≤ 10th %ile). We then compared agreement between the batteries at each of those levels. Results More soldiers with mTBI had low scores than healthy soldiers on both batteries. Of the soldiers who performed at the worst level on one battery, 95.1% from CogState and 70.6% from traditional had some level of poor performance on the other battery. However, of the soldiers who performed at the worst level on either battery, only 31.7% from CogState and 38.2% from traditional also performed at the worst level on the other battery. Conclusion These batteries similarly identify poor performance to a degree, though with some potentially meaningful differences still present.

A-232 Using Rates of Low Scores to Assess Agreement between ImPACT and a Traditional Battery of Neuropsychological Tests

Abstract Objective ImPACT is a brief computerized test battery used to assess cognitive function most often following sports concussion. We compare intra-individual agreement between ImPACT and a battery of traditional neuropsychological tests using rates of low scores. Methods Complete and valid data from 246 healthy soldiers and 177 soldiers ≤ 7 days from sustaining mild TBI (mTBI) were used in this analysis. All soldiers were consecutively administered ImPACT and a traditional test battery consisting of: TOPF, WAIS-IV, CVLT-II, RCFT, DKEFS, and CPT-II. We performed base rate analyses of both batteries to determine the proportions of soldiers who had various numbers of scores that were 1.0+, 1.5+, and 2.0+ standard deviations below the normative mean. We used those rates to place Soldiers into a “low score hierarchy” ranging from the least poor (i.e. ~ > 10th %ile) to the worst overall performance (i.e. ~ ≤ 10th %ile). We then compared agreement between the batteries at each of those levels. Results More soldiers with mTBI had low scores than healthy soldiers on both batteries. Of the soldiers who performed at the worst level on one battery, 100.0% from ImPACT and 73.1% from traditional had some level of poor performance on the other battery. However, of the soldiers who performed at the worst level on either battery, only 42.9% from ImPACT and 34.6% from traditional also performed at the worst level on the other battery. Conclusion These batteries similarly identify poor performance to a degree, though with some potentially meaningful differences still present.

A-248 Using Rates of Low Scores to Assess Agreement between CNSVS and a Traditional Battery of Neuropsychological Tests

Abstract Objective CNSVS is a brief computerized test battery used to assess cognitive function. We compare intra-individual agreement between CNSVS and a battery of traditional neuropsychological tests using rates of low scores. Methods Complete and valid data from 246 healthy soldiers and 177 soldiers ≤ 7 days from sustaining mild TBI (mTBI) were used in this analysis. All soldiers were consecutively administered CNSVS and a traditional test battery consisting of: TOPF, WAIS-IV, CVLT-II, RCFT, DKEFS, and CPT-II. We performed base rate analyses of both batteries to determine the proportions of soldiers who had various numbers of scores that were 1.0+, 1.5+, and 2.0+ standard deviations below the normative mean. We used those rates to place Soldiers into a “low score hierarchy” ranging from the least poor (i.e. ~ > 10th %ile) to the worst overall performance (i.e. ~ ≤ 10th %ile). We then compared agreement between the batteries at each of those levels. Results More soldiers with mTBI had low scores than healthy soldiers on both batteries. Of the soldiers who performed at the worst level on one battery, 95.9% from CNSVS and 80.0% from traditional had some level of poor performance on the other battery. However, of the soldiers who performed at the worst level on either battery, only 38.8% from CNSVS and 63.3% from traditional also performed at the worst level on the other battery. Conclusion These batteries similarly identify poor performance to a degree, though with some potentially meaningful differences still present.

B-45 Base Rates of Low Scores on a Traditional Battery of Neuropsychological Tests in Soldiers with and without Acute mTBI

Abstract Objective It is not uncommon for healthy individuals to have one or more low scores on a battery of cognitive tests. The number of scores produced by the battery by itself can affect the probability of having low scores. The purpose of this study is to examine the rates of low scores on a battery of commonly used neuropsychological tests in soldiers with and without acute mTBI. Methods Data from 246 healthy soldiers and 177 soldiers evaluated within seven days of sustaining a mTBI and who had complete and valid data were used in this analysis. All soldiers completed the TOPF, WAIS-IV, CVLT-II, RCFT, DKEFS, and CPT-II. The CARB was used as a measure of effort. For each group, we determined the proportions of soldiers who had various numbers of scores that were 1.0 or more, 1.5 or more, 2.0 or more standard deviations below the normative means for each score. We used prevalence ratios to compare the proportions with low scores in each group. Results Low scores were common in both groups (93.1% and 96.0% of controls and mTBI cases, respectively, had at least one score 1.0+ SDs below norm, 57.7% and 79.1% had at least one score 1.5+ SDs below norm, while 30.5% and 48.0% had at least score 2.0+ SDs below norm). Low scores were more common in the mTBI group. Conclusion Examining rates of low scores can help identify clinically meaningful performance decrements across an entire battery when large numbers of scores are available.

B-74 Using Rates of Low Scores to Assess Agreement between ANAM4 TBI-MIL and a Traditional Battery of Neuropsychological Tests

Abstract Objective The Automated Neurological Assessment Metrics (Version 4) Traumatic Brain Injury Military (ANAM4 TBI-MIL) battery is widely used by the US military to assess cognitive function. We compare intra-individual agreement between ANAM4 TBI-MIL and a battery of traditional neuropsychological tests using rates of low scores. Methods Complete and valid data from 246 healthy soldiers and 177 soldiers ≤7 days from sustaining mild TBI (mTBI) were used in this analysis. All soldiers were consecutively administered ANAM4 TBI-MIL and a traditional test battery consisting of: TOPF, WAIS-IV, CVLT-II, RCFT, DKEFS, and CPT-II. We performed base rate analyses of both batteries to determine the proportions of soldiers who had various numbers of scores that were 1.0+, 1.5+, and 2.0+ standard deviations below the normative mean. We used those rates to place Soldiers into a “low score hierarchy” ranging from the least poor (i.e. ~≥10th %ile) to the worst overall performance (i.e. ~≤10th %ile). We then compared agreement between the batteries at each of those levels. Results More soldiers with mTBI had low scores than healthy soldiers on both batteries. Of the soldiers who performed at the worst level on one battery, 88.1% from ANAM and 100% from traditional had some level of poor performance on the other battery. However, of the soldiers who performed at the worst level on either battery, only 58.3% from ANAM and 50.0% from traditional also performed at the worst level on the other battery. Conclusion These batteries similarly identify poor performance to a degree, though with some potentially meaningful differences still present.

Improving risk prediction accuracy for new soldiers in the U.S. Army by adding self-report survey data to administrative data

BackgroundHigh rates of mental disorders, suicidality, and interpersonal violence early in the military career have raised interest in implementing preventive interventions with high-risk new enlistees. The Army Study to Assess Risk and Resilience in Servicemembers (STARRS) developed risk-targeting systems for these outcomes based on machine learning methods using administrative data predictors. However, administrative data omit many risk factors, raising the question whether risk targeting could be improved by adding self-report survey data to prediction models. If so, the Army may gain from routinely administering surveys that assess additional risk factors.MethodsThe STARRS New Soldier Survey was administered to 21,790 Regular Army soldiers who agreed to have survey data linked to administrative records. As reported previously, machine learning models using administrative data as predictors found that small proportions of high-risk soldiers accounted for high proportions of negative outcomes. Other machine learning models using self-report survey data as predictors were developed previously for three of these outcomes: major physical violence and sexual violence perpetration among men and sexual violence victimization among women. Here we examined the extent to which this survey information increases prediction accuracy, over models based solely on administrative data, for those three outcomes. We used discrete-time survival analysis to estimate a series of models predicting first occurrence, assessing how model fit improved and concentration of risk increased when adding the predicted risk score based on survey data to the predicted risk score based on administrative data.ResultsThe addition of survey data improved prediction significantly for all outcomes. In the most extreme case, the percentage of reported sexual violence victimization among the 5% of female soldiers with highest predicted risk increased from 17.5% using only administrative predictors to 29.4% adding survey predictors, a 67.9% proportional increase in prediction accuracy. Other proportional increases in concentration of risk ranged from 4.8% to 49.5% (median = 26.0%).ConclusionsData from an ongoing New Soldier Survey could substantially improve accuracy of risk models compared to models based exclusively on administrative predictors. Depending upon the characteristics of interventions used, the increase in targeting accuracy from survey data might offset survey administration costs.

Using self-report surveys at the beginning of service to develop multi-outcome risk models for new soldiers in the U.S. Army.

The U.S. Army uses universal preventives interventions for several negative outcomes (e.g. suicide, violence, sexual assault) with especially high risks in the early years of service. More intensive interventions exist, but would be cost-effective only if targeted at high-risk soldiers. We report results of efforts to develop models for such targeting from self-report surveys administered at the beginning of Army service. 21 832 new soldiers completed a self-administered questionnaire (SAQ) in 2011-2012 and consented to link administrative data to SAQ responses. Penalized regression models were developed for 12 administratively-recorded outcomes occurring by December 2013: suicide attempt, mental hospitalization, positive drug test, traumatic brain injury (TBI), other severe injury, several types of violence perpetration and victimization, demotion, and attrition. The best-performing models were for TBI (AUC = 0.80), major physical violence perpetration (AUC = 0.78), sexual assault perpetration (AUC = 0.78), and suicide attempt (AUC = 0.74). Although predicted risk scores were significantly correlated across outcomes, prediction was not improved by including risk scores for other outcomes in models. Of particular note: 40.5% of suicide attempts occurred among the 10% of new soldiers with highest predicted risk, 57.2% of male sexual assault perpetrations among the 15% with highest predicted risk, and 35.5% of female sexual assault victimizations among the 10% with highest predicted risk. Data collected at the beginning of service in self-report surveys could be used to develop risk models that define small proportions of new soldiers accounting for high proportions of negative outcomes over the first few years of service.

Two Closely Related Species of Desert Carpenter Ant Differ in Individual‐Level Allocation to Fat Storage

Comparison of closely related species that differ in their life histories is a powerful method for studying the underlying physiological mechanisms contributing to life-history variation. I investigated whether two closely related members of the Camponotus festinatus species complex of desert carpenter ants, C. nr. festinatus Desert Light and C. nr. festinatus Desert Dark, differed in their life-history tactics with respect to fat storage. Newly mated queens were collected in the field, and colonies were reared under common conditions in the laboratory for 2 yr before sampling. I show that the two species differ in fat storage at the individual level. While the basic scaling relationship between lean mass and fat content did not differ between the two species, Dark workers and soldiers stored significantly more fat per unit lean mass than Light workers or soldiers. There were no significant demographic differences in the proportions of workers or soldiers involved in fat storage between the two species, although there was a trend toward Light colonies having a greater proportion of soldiers storing large amounts of fat. There was also no significant difference in the total amount of fat stored by the two species at the colony level. The detection of strong individual-level effects but no colony-level effects was likely due to the low statistical power of colony-level analyses. Showing that these two closely related species differ in fat storage at the individual level in a common environment demonstrates their utility as a model for understanding the physiological and behavioral mechanisms regulating life-history variation in fat storage in ants.

Formosan Subterranean Termite (Isoptera: Rhinotermitidae) Wood Consumption and Worker Survival as Affected by Temperature and Soldier Proportion

The effect of temperature and soldier proportion on worker survival, soldier production, and wood consumption of the Formosan subterranean termite, Coptotermes formosanus Shiraki, was evaluated in the laboratory with termites from a single colony. Soldier production was influenced by temperature and the initial proportion of soldiers. On average, termites had a significantly higher survival rate when the initial soldier proportion was <20%. Soldier caste development was at its highest at 30°C, and when treatment started with no soldiers in the colony. Termite survival was significantly higher at 30°C than at 25 and 33°C after 12 d of testing. There was a significant interaction of temperature and soldier proportion on termite survival after 36 d. C. formosanus could support higher proportions of soldiers with an increase in temperature. There was no significant decrease in survival rates with increasing numbers of soldiers at 25 and 33°C. At 60 d, survival at 20 and 25°C declined significantly when soldier proportions exceeded 20%. At 30 and 33°C, termite survival did not decline significantly when soldier proportions increased from 20 to 30% (30°C) or 40% (33°C). Consumption rates increased significantly with rising temperature up to 30°C. Consumption rates tended to increase as soldier proportion increased. There was no significant interaction between temperature and soldier proportion on wood consumption rate.

Genetic influence on caste in the ant Camponotus consobrinus

Genetic influences on polyethism within social insect colonies are well known, suggesting that the determination of caste (soldiers and minor workers) may also be genetically mediated. The Australian sugar ant Camponotus consobrinus is suitable for such a study, having soldiers and minor workers that follow a complex allometry. Further, although most C. consobrinus colonies are monogynous, 13 of 42 surveyed using microsatellites were found to be polygynous. Thus, although a minority of colonies were polygynous, the great majority of queens live in polygynous colonies. From the 29 monogynous colonies studied, we inferred that the queens are monandrous. Ants from four polygynous colonies were assigned to families on the basis of microsatellite genotypes, after measurements had been taken of head width and scape length. These measurements reflect a complex allometry interpretable as soldier and minor worker growth curves with a large changeover zone. Genetic influence on caste determination was examined by testing for differences between families within colonies in the distribution of scape lengths, residuals from the overall colony allometric curve, and proportions of soldiers and minor workers (as determined by head width falling above or below the inflection point of the overall colony allometric curve). Families in all four colonies differed significantly in caste proportions and in head-width distributions, and three of the four colonies showed significant differences between families in residuals from the overall colony growth curve. Nested ANOVAs using head widths and scape-length residuals showed that when the effect of family is removed, intercolony differences in allometry are negligible. This evidence indicates genetic rather than environmental causes for the observed differences between families. We speculate that this variation may reflect some selective advantage to within-colony heterogeneity between families or that selective differences are few between a wide array of family growth patterns.

Soldiers effectively defend aphid colonies against predators in the field

Morphologically specialized soldiers occur in more than 50 aphid species in the families Pemphigidae and Hormaphididae. To study the effectiveness of soldiers of the gall-forming aphid,Pemphigus spyrothecaePass., in protecting their galls against natural levels of predation, we manipulated the proportions of soldiers and non-soldiers in sets of galls still attached to poplar trees in the field. Galls with 50 soldiers and 50 non-soldiers were approximately 10 times less likely to be attacked by predators than galls that contained 100 non-soldier aphids. There were significantly fewer live aphids, and significantly more dead aphids, in galls without soldiers than in galls protected either by soldiers or by being within a bag. There were no significant differences in the survival of aphids in galls protected by soldiers compared with those protected by bagging. The soldiers did not protect the galls against invasion by the cohabiting aphidChaitophorus leucomelasKoch. These observations provide the first demonstration that soldiers are effective in defence against natural levels of predation under field conditions.

A Test of Optimal Caste Ratio Theory Using the Ant Camponotus (Colobopsis) Impressus

Oster and Wilson developed theoretical models predicting optimal caste ratios for social insects. We have tested some of these predictions in the field using an ant species that fits the relevant assumptions of their models. The ant Camponotus (Colobopsis) impressus has two worker castes: major workers (=soliders), which guard the nests and may also store food, and minor workers (=workers), which are responsible for foraging. For such a species, Oster and Wilson predicted a concave relationship between the number of soldiers and the number of workers in the breeding season, and a convex relationship in the nonbreeding season. These predictions were supported by field censuses of C. impressus colonies. Also, increased proportions of soldiers (number of soldiers per worker) were found in the breeding versus the nonbreeding season, as predicted by the models. However, although the models predicted that breeding caste ratios should be optimal from the point of view of reproductive success, in C. impressus the production of alates was positively correlated with the number of soldiers, implying that the population had not reached the optimal caste ratio functions predicted by theory. Data on colony growth patterns and ecological variables suggested that the lack of a complete fit between theory and results was due to several oversimplified assumptions about the proximal mechanisms of caste ratio regulation. C. impressus actively altered caste ratios on a seasonal basis and on an ontogenetic basis, but there was no evidence of any adjustments to annual or spatial variations in resources, competitors or predators. Moreover, laboratory experiments in which different proportions of soldiers were removed revealed that the ability of C. impressus to regulate caste ratios was severely constrained by a low, constant production ratio of new soldiers to new workers. The existence of physiological and temporal constraints to caste ratio adjustments should be taken into account in studies of caste ratios for social insects.

Production of soldiers and maintenance of soldier proportions by laboratory experimental groups ofReticulitermes flavipes (Kollar) andReticulitermes virginicus (Banks) (Isoptera:Rhinotermitidae)

The effects of group size, time of year, and initial proportions of soldiers were explored in experimental groups ofReticulitermes flavipes (Kollar) andR. virginicus (Banks). Groups were held in the laboratory for 12 weeks. Small groups (500 to 1000 workers) produced a smaller percentage of soldiers than did larger groups (1500 to 2500 workers). The number of soldiers produced in a group is highly correlated with the total number of termites surviving. The average percentage produced for all group sizes was 1.75 for both species.

THE EFFECT OF SEPARATION BY “PAPERING” ON CASTE RATIOS IN NASUTITERMES EXITIOSUS (HILL) (ISOPTERA)

AbstractThe separation by “papering” of Nasutitermes exitiosus from broken mound material provides a sample of termites containing higher proportions of small soldiers, second to fifth stage large workers, and alates, and lower proportions of larvae, first stage workers, presoldiers, and workers near to ecdysis, than occur in the termites that remain in the mound material. These differences can be correlated with differences in the behaviour of the various castes and stages when the nest is damaged.