Affects of Nest Availability on Behavior of Crawfordapis luctuosa, a solitary bee Erika Blackwell Department of Biology, University of Minnesota _____________________________________________________________________________________ Abstract Intra specific interference competition behavior arises when one organism prevents another from utilizing a resource Begon, et al. 1990. This resource can be mating partners, a food source, or habitat, but it is often less expensive for the organism to defend the reso urce than to find another. In this study, 60 nest hole entrances were barred in percentages of 25%, and 50%, in order to study the interactions of Crawfordapis luctuosa Apoidea, Colletidae, Diphaglossinae in the presence of depleted nest hole availabilit y. The study was conducted in Monteverde, Puntarenas Province, Costa Rica, at a large nest aggregation approximately 1740 meters in elevation on Cerro Amigos. It was found that with an increasing number of holes covered, the mean lengths of visits increase d t Test, F = 3, 452, P = .032, as well as the incidence of long visits FisherÂ€s PLSD post hoc, MD = .407, P = .044, and long visits from 25% of 50% coverage FisherÂ€s PLSD post hoc test, MD = .612, P = .003. It was also found that with an increasing percentage of holes covered, crawling and digging behavior increased chi square test, X 2 = 6.533, df = 2, P = .038, as well as the overall incidence of aggressive interactions chi square test, X 2 = 25.609, df = 2, P < .05. Also, twenty six new nest hol es were con s tructed during the study. It was hypothesized that the bees who spent the most time digging were also the main participants in aggressive interactions. These were ÂprovisioningÂ‚ females with a high energetic investment in a single nest. These a ggressive interactions in C. luctuosa are previously unobserved, and therefore makes C. luctuosa an excellent subject for the study of competition and evolution of sociality. Resumen La conducta intra especfica de la competencia de interferencia surge cuando un organism o previene otro de utiliza r un recurso Begon, et al. 1990. Este recurso puede estar apareando a socios, una fuente de alimento, o el hbitat, pero es a menudo menos costoso para el or ganismo para defender el recurso que encontrar otro. En este estudio, 60 entradas de hoyo de nido se impidieron en porcentajes de 25%, y 50%, para estudian las interacciones de Crawfordapis luctuosa Apoidea, Colletidae, Diphaglossinae en la presencia de la disponibilidad agotada de hoyo de nido. El estudio se condujo en Monteverde, la Provincia de Puntarenas, Costa Rica, en una agregado grande del nido aproximadamente 1740 contadores en la elevacin en Cerro Amigos. Se encontr que con un nmero creciente de hoyos cubri, los promedios de las longitudes de visitas aumentadas t Test, F = 3, 452, P = .032, as como la incidencia de visitas largas FisherÂ€s PLSD post hoc test, MD = .407, P = .044, y las visitas largas de 25% de 50% de alcance FisherÂ€s PLS D post hoc test, M D = .612, P = .003. Se encontr tambin que con un porcentaje creciente de hoyos cubri, arrastrndose y la conducta que cavan aumentado chi square test, X 2 = 6.533, df = 2, P = .038, as como la incidencia general de interacciones agr esivas chi square test, X 2 = 25.609, df = 2, P < .05. Tambin, hoyos nuevos veintisis de nido se contructed durante el estudio. Fue formado una hiptesis que las abejas que gastaron las la mayora de los tiempos que cavan eran tambin los participantes principales en interacciones agresivas. Estos eran ÂprovisioningÂ‚ hembras con una inversiÂƒn alto energtica en un solo nido. Estas interacciones agresivas en C. luctuosa es previamente inadvertido, y
por lo tanto las marcas C. luctuosa un sujeto excelente para el estudio de la competencia y la evolucin de sociality. Introduction The need for resources has created species interactions such as predation, parasitism, mutualism, and competition. Competitive interactions arise when demand for a particular re source exceeds the supply available Begon, et al. 1990, and intra specific competition may be especially destructive because individuals are vying for exactly the same resources. In most cases of competition, conspecifics do not interact directly with on e another, but instead respond to the level of the resource left after the use of other individuals. This may be described as Âexploitation Begon, et al. 1990.Â‚ Another type of competition is called Âinterference,Â‚ when individuals interact directly and one individual prevents another from occupying or exploiting a resource Begon, et al. 1990. Many times it is less energetically expensive to defend this resource than to search for a new one. One example is territoriality, or interference competition for the purpose of defending living space. Hymenopterans are not typically characterized by aggressive behavior, but instead by their sociality. Eusocial species can be identified by three distinctive traits: presence of divisions of labor or reproductive ca stes, females cooperate in nesting, and an overlap of generations that contribute to colony labor Wilson 1971. This evolution of altruism in hymenopterans was originally considered by even Darwin as potentially damaging to theories of natural selection Krebs and Davies 1981. However, sociality in hymenopterans may have developed as a result of competition for common resources. Advantages for living in a group may include shortage of nesting space Hanson and Gauld 1995, defense against parasites or pre dators Krebs and Davies 1981, more efficient usurpation of resources, thermoregulation or social homeostasis Wilson 1971, and cooperation in raising young. Although the eusocial species are the best studied, organisms in Hymenoptera range from complet ely solitary species to those which are highly eusocial Brockmann 1984. Crawfordapis luctuosa Apoidea, Colletidae, Diphaglossinae is a type of pre social ground nesting bee. This large, robust, black bee has only been observed in a few localities from Mexico to Western Panama Roubik 1984, and prefers to nest in aggregations on exposed clay sites at altitudes above 1500 meters Otis et al. 1982. Individuals can be as long as 24 mm and typically show dense pubescence with a few reddish hairs located la terally near the posterior of the metastoma Hubbard, 1997. Female ÂprovisioningÂ‚ bees exhibit high nest fidelity, or tend to return to the same nest when they are provisioning young Wuellner and Jang 1996. ÂFloaterÂ‚ females, typically maiden females or females who have finished provisioning, show low nest fidelity, continuously searching for nest vacancies Jang, et al. 1995. Males tend to spend the day flying in Âirregular sinuous courses,Â‚ chasing any airborne object Wuellner and Jang 1996 and occa sionally pouncing on females and knocking them to the ground Roubik 1984.
Little aggression or territoriality has been observed between female bees. Although each female may lay only a few eggs in her nest, many studies have given evidence to the fact t hat ownership is not restricted to one female per nest Calabrese 1998; Otis, et al. 1982. More often, multiple females in a single nest at the same time show no aggression. There have also been incidents where female bees entering a nest already occupied by a resident female encountered a loud buzzing, and the intruding bees left quickly Otis 2000. In a previous study by Calabrese 1998, all aerial chases caught were composed of males and females, which suggested mating behavior and no territorial guar ding behavior between females or males. Given the close proximity of the nest holes to one another, and hypotheses of provision stealing and nest takeovers Otis, et al. 1982, none of these antagonistic behaviors have been observed to a significant degree in C. luctuosa One explanation for the lack of aggression in C. luctuosa females may be that they are not competing for any resources. Other ground burrowing species, such as Sphex ichneumoneus a Sphecid wasp, have been observed to fight over nest holes when there is a lack of available space Brockman, et al. 1979, cited by Krebs and Davies 1981. The female wasps searching for a nest practice a ÂenteringÂ‚ or ÂdiggingÂ‚ strategy depending on how many nest holes are available and which strategy has the highest probability of success. Because th ere is a considerable energetic cost involved in digging a nest, the femaleÂ€s persistence in fighting is directly related to her investment in the nest Brockman, et al. 1979, cited by Krebs and Davies 1981. Like the female S. ichneumoneus C. luctuosa in vests a considerable amount of energy in constructing a nest. These nests may be long lasting and reusable, and therefore it may be more cost efficient for the female C. luctuosa to fight for a nest rather than dig a new one when nesting resources are scar ce. This situation has not been previously observed. To test the hypothesis that lack of aggressive behavior in C. luctuosa is due to non competitive nest use, I covered varying percentages of nesting holes, reducing the number of available nest cavities. This easy manipulation effectively created an increasing likelihood of competition. I analyzed the visitation of holes by multiple females, length of visits by female bees, hole recovery or construction by crawling and digging, and the incidence of aggres sive encounters. I hypothesized that if Crawfordapis luctuosa is truly solitary, it will a exhibit intra specific interference competition with a reduction in nest hole space available, and if not b Crawfordapis luctuosa females will cooperate in the eve nt of depleted nest hole space, or c interact randomly, neither attracting nor inhibiting each otherÂ€s search for nest space, as supported in previous studies. Methods Study Site The study was conducted in Monteverde, Puntarenas Province, Costa Rica on Cerro Amigos, a service road leading to the television towers, from late April to early May. The study site was at approximately 1740m in elevation, and nests were densely aggregated
on the sides of the packed clay road as well as the nearly vertically rising embankments. The surrounding vegetation, aside from the disturbed road edge, is best described as Cloud Forest. Sixty nest holes were designated for study, in an area measured 4.44m 2 The holes were marked with numbers printed on computer paper and affixed onto pieces of heavy cardboard with silicon glue. The squares of cardboard were held in place with nails approximately one inch in length driven into the ground. Hole Usage Entrances and exits by female C. luctuosa bees were observed for 6 days from 0920 to 1220h. The number of seconds for each visit was timed with a watch and recorded, along with the time of day and hole number. Later, visits by female bees were separated into classes of long visits one minute and over and short visits less than one minute. These categories were based on a distinction originally made by Otis et al. 1982, who suggested any visits one minute or less were likely to have been Âexploratory visitsÂ‚ rather than Âworking visits.Â‚ Any instances of two or more bees being simultaneously present in the holes were recorded as well. After two days of observation, the 60 nest holes were covered using Costa Rican colones coins. Each pile of coins was arranged to be heavy enough so that the f emale C. luctuosa bees were unable to push off the coins blocking their nest entrances. The percentage of holes covered each day was 25%, or 50%. These percentages were called Âtreatments,Â‚ and data were recorded for two consecutive days of each treatment. Treatment days were paired in order to test for trends within the two days of each treatment, perhaps caused by an awareness of the C. luctuosa females of reduced nest availability. After two days of treatment, there was a day without treatment. This prov ided time for the bees to recover from the prior treatment and resume normal activity. The same holes were not covered every day, but chosen randomly at the start of each observation period. At the end of each three hour observation period, the coins were removed to allow the females to re enter the nests. To assess any trends of Âworking visitsÂ‚ or Âexploratory visits,Â‚ the number of long and short visits was totaled for each hole during each two day treatment and tested with a one way ANOVA. The length i n seconds of each visit was also compared to the percentage of holes covered using a one way ANOVA. The outcome of treatment on the average length of visit per day was analyzed with a t Test. Three separate Chi squared tests were used to analyze difference s between the total numbers of holes which never received any visits, those which were observed to have single bee visits, and those in which two bees simultaneously occupying the hole were observed. These three categories were all compared to the percenta ge of holes covered. Trends in the number and length of visits may have suggested increased searching for nesting space, or lack thereof, which may suggest searching elsewhere. A difference within the days of the treatments may have suggested a awareness within the females that would have caused them to search for longer periods of time as the days progressed. An increase in the incidents of multiple females in the same nest could have potentially shown cooperation when there is a shortage of nesting sites available. No positive trends
would suggest female C. luctuosa bee behavior is not affected by limited nest hole space, and continues to act randomly. Investment in Hole Recovery Behavior exhibited by female C. luctuosa normally associated with finding their nest or building a new nest was also timed and recorded. Searching or feeling on the ground near a covered hole was termed Âcrawling,Â‚ while removing earth with the forelegs and digging a new tunnel or around a coin was termed Âdigging.Â‚ The time spent crawling and digging during zero percent, 25%, and 50% of holes covered were analyzed with a two way ANOVA and a chi square test was used to examine the incidence of crawling and digging observed compared to the percen tage of holes covered. Finally, a t Test was used to compare the amount of time spent crawling and digging this time considering them similar behaviors by lumping them together to the percentage of holes covered. An increase in digging, crawling, or time spent on these activities may have indicated females who are either a searching for their own nest, b burrowing to it through an alternate tunnel, or c searching for an optimal place to construct a new nest hole. A non significant trend would have sugg ested these females have not already invested heavily in their nest and find it more profitable to find a new one or share a hole with another female bee. Aggression Any visible aggressive interactions were timed and reported. This included aerial chases aerial chases involving over two bees, aerial Âhead butting,Â‚ tackling, and wrestling on the ground. Aggressive actions were further divided into those located on the ground, and those located in the air. This was to investigate the identities of the agg ressive bees. For instance, aggressive pairs directly over holes may have been likely to be composed of females protecting their nest, while aerial aggressive pairs may have consisted largely of male female chases. Over all incidents of aggression, incide nce of each type of aggression, and the aggressive incidents per day were compared to the type of treatment using Chi squared tests. An over all positive trend would have indicated increasing aggressive behavior displayed by the bees with an increasing per centage of holes covered. In order to gain insight into which bees were displaying aggressive behavior, as many aggressive pairs as possible were netted out of the air and the sex determined of the participants. A large amount of female female aggressive p airs could have suggested competition for available holes and/or nest space among female C. luctuosa bees. On the other hand, dominance of male female pairs could suggest increasing advances on females from males searching for mating partners.
Results Hole Usage Overall, 755 visits were recorded over the three day period, the average duration of visit being 34.42 seconds. The mean length of visit was found to increase with an increasing percentage of holes covered, from 26.99, to 33.42, to 46.23 T te st, F = 3.452, P = .032 Figure 2, but showed no statistical difference when broken down between days of treatment Figure 1. Short visits were more common than long visits, totaling 639 and 121, respectively. The effect of percent coverage on the avera ge number of short visits below one minute per hole was found to be statistically non significant two way ANOVA, MS = 1.1 F = .115, P = .8912. The mean number of long visits, however, increased significantly from .745, to .540, to 1.152. This was foun d significant from zero percent to 50% and from 25% to 50% Figure 3. Three Chi squared tests were performed to examine differences between the number of female bees present in each hole. This was done using the total number of holes with zero visits, th ose with only single female visits, and lastly, holes which had visits of two females at the same time. Expected values for each test were adjusted for the number of holes which were actually open during each treatment. In all cases, an increase in the per centage of holes covered caused no statistical difference in these categories X 2 = 1.06, 1.67, .239 respectively, df = 2, P > .05. Investment in Hole Recovery Data were recorded on 73 incidents of digging and crawling, the longest incident of digging l asting 12240 seconds, and the average incident lasting 247.233 seconds. Out of the total, 29 incidents were of bees crawling on the ground close to covered holes. In these incidents, the bees were not attempting to remove any earth, but simply appeared to be examining the coins covering the hole and the surrounding area. Most of the other 24 incidents involved females trying to dig around the coins, but three incidents involved digging alternate tunnels into a nest, and three involved digging what appeared to be new holes. During the six days of data collection, I also found 26 new holes in the ground. I am unable to report with confidence the exact day each hole appeared. It was found that there was a significant increase in the incidence of digging and cr awling activity with an increasing percentage of holes covered X 2 = 6.533, df = 2, P = .038 Figure 4. There was an increase from 65.6 to 315.774 seconds in the meantime length of crawling and digging incidents from the 25% to the 50% treatment, but it was found to be insignificant when the activities were separated ANOVA, F = .817, P = .369, and also when both activities were linked together as a single measure Figure 5. Aggression One hundred and thirty eight aggressive encounters were recorded, the longest lasting two minutes and four seconds. Of these, 39 took place on the ground, and 99 took place
in the air. Many of these encounters were chases or aerial Âhead butting.Â‚ Other times a one bee would appear to pounce on another bee and wrestle with it on the ground. There were instances a pair would tumble on the ground, while at other times a pair would stay in one place, presumably mating. Also, there were severa l aerial chases involving three or four bees at one time. A chi square test found that there was a significant increase in the overall incidents of aggression with an increasing percentage of holes covered X 2 = 25.609, df = 2, P < .05 Figure 6. When br oken down into aerial aggression and ground aggression, it was also found that an increasing percentage of holes covered caused a significant increase in aggression in the air X 2 = 13.516, df = 2, P < .05, while the difference was statistically non signi ficant for ground aggression X 2 = 4.663, df = 2, P > .05 Figure 7. The difference in aggression within the days of each treatment was also found to be significant X 2 = 12.362, df = 2, P = .002, although the incidents of aggression decreased on the s econd day of 50% holes covered Figure 8. Out of the ten chases netted during a day with 50% of holes covered, five of the pairs caught were composed of two females, four of which occurred near covered holes, and one that was located in the air. Four of t he pairs caught in the air were composed of one male and one female, and the last aerial pair was composed of two males. Discussion The purpose of this study was to examine the aggressive and territorial behavior of C. luctuosa with reduced amounts of n esting sites available. Nest holes of varying percentages were covered up in amounts of zero percent, 25%, and 50%. Results in this experiment were intended to be used to support one of three hypotheses: If Crawfordapis luctuosa is truly solitary, it will a exhibit intra specific interference competition with a reduction in nest hole space available, and if not b Crawfordapis luctuosa females will cooperate in the event of depleted nest hole space, or c interact randomly, neither attracting nor inhibitin g each otherÂ€s search for nest space. It has been stated that competitive interactions arise when there is a limiting resource, and competitive interference normally occurs when it is more cost effective to protect a particular resource than find a new one It was found that the mean length of hole use significantly increased with an increasing percentage of holes covered. I believe this could indicate that C. luctuosa females are expending more time and energy on nest location. This would support an idea originally prop osed by Jang et al. 1995: when there are less available nests for provisioning, there are more ÂfloatingÂ‚ females. This study also found that the incidence of long visits increased with more coverage of holes. This means that not only are searches by C. luctuosa females becoming longer, but they are also more frequent as well. The increased visit lengths are most likely due to a concentrated effort to locate new nests, but it could also be an initiation of a coo perative or joint nest ownership. It was observed that the numbers of nests receiving zero visits, only single female visits, and visits with two females simultaneously did not differ significantly with treatment. This says that proportionally, colony nes ts were not experiencing a reduction
or increase in the amount of nests receiving visits from two females at the same time. This does not suggest that females were becoming more cooperative, but instead that they continued to randomly search for nests when the nest space was reduced. This could also be an indication of inhibition of multiple visits by increased interference competition. There was a significant increase in the incidence of digging and crawling activity with the percentage of holes covered, but not a significant increase in the length of these incidents. The increase in crawling, may suggest an investigative behavior exhibited by the bees, while the digging may indicate attempts at nesting hole recovery. Eighteen out of the 24 digging in ciden ts involved C. luctuosa bees digging around the coins. I hypothesize these bees were females with large energetic investments in one nest. These bees were investing more time in attempting to recover their nests because the cost of nest abandonment outweig hed the costs of defending or rebuilding it. This dramatic increase in digging behavior may have been the cause of the 26 new nesting holes I recorded during the study. Such a large number of new holes have been recorded before, most likely because the C. luctuosa bees were never forced to compete for nesting habitat. Aggression significantly increased with the percentage of holes covered, suggesting that the C. luctuosa bees were involved in intra specific interference competition similar to that of the S ichneumoneus I would hypothesize that most of these interactions involved female provisioning bees, because they had an active nest to defend and therefore the most to lose. More interestingly, incidents of aggression increased within the treatment from day one to day two as well. This may suggest a certain awareness on the part of the bees that there was decreasing nest space, prompting them to be more aggressive at staking out territory and defending it. Another explanation for this could be that the m ale bees took the opportunity to search for new mating partners because of the unusual amount of female bees barred from returning to their nests. This however, occurred only 40% of the time in the experiment, while 50% of the time, the aggressive pairs ne tted consisted of two female bees. On a small temporal scale, an increase in aggression and digging be havior was observed in C. luctuosa when nesting space was limited. Because of this, I believe that the increase in aggressive behavior observed was due t o female intra specific interactions. However, a longer study focused only on aggression with decreasing nesting habitat and perhaps involving marking individual female bees might be helpful in solidifying this argument. This aggressive behavior in C. luct uosa is previously unobserved, and is similar to the behavior of other solitary ground burrowing hymenopterans, such as the digger wasp S. ichneumoneus However, because C. luctuosa is nesting in an aggregation and is exhibiting antagonistic behavior in th e presence of a limiting resource, it is interacting. Crawfordapis luctuosa therefore, is an excellent subject for the study of competition and evolution of sociality. Some questions suitable for exploration include; when does it become more cost effectiv e to cooperate than to compete, and what prompted the change to altruism in eusocial insects?
Acknowledgements I would like to thank Alan Masters for providing inspiration, guidance, and support during this project, your enthusiasm was always greatly appreciated. I also thank Andrew Rodstrom for graciously agreeing to help me with everything from catching bees to r ehabilitating computers, and Rick Smith for his patience and help with photography. In addition, many thanks to Mauricio Garcia for helping initiate this project, and Karen Masters for her encouragement and advice. I would like to thank all of the staff at Las Torres del Televisin for allowing me to conduct my experiment unimpeded, and for their continued interest in my work. I am deeply grateful and thank the Alvarado Snchez family for inviting me into their home and hearts. Finally, a special thanks goe s out to Tracy and Andrea for their humor, conversation, and friendship. Literature Cited Begon, Micheal, Harper, John L., and Townsend, Colin R. 1990. Ecology Individuals, Populations, and Communities. Blackwell Scientific Publications, Cambridge, MA, U SA, pp. 340 361 Brockmann, Jane H. 1984. The Evolution of Social Behavior in Insects. In: Behavioral Ecology An Evolutionary Report Krebs, J.R. and Davies, N.B. eds. Sinauer Associates Inc., Sunderland, MA, USA. Pp. 340 361. Calabrese, J.H. 1998. Nesting behavior and Natural History of Crawfordapis luctuosa Spring 1998 CIEE Tropical Biology Program. Unpublished. Hanson, P.E., and Gauld, I.D. eds. 1995. The Hymenoptera of Costa Rica. Oxford University Press. Oxford, UK. Hubbard, K.M. 1997. Nesting Behavior of Crawfordapis luctuosa Fall 1997 CIEE Tropical Biology Program. Unpublished. Jang, Yikweon, Wueller, Clare T., and Scott, Christina S. 1995. Floating and fidelity in Nest Visitation by Crawfordapis luctuosa Hymenoptera: Colletidae. Journal of Insect Behavior 9: 3: 493 504. Krebs, J.R., and Davies N.B. 1981 An Introduction to Behavioral Ecology Sinauer Associates, Inc ., Sunderland, MA 01375, USA Otis, Gard. 2000. Crawfordapis luctuosa a Ground Nesting Bee of the Central American H ighlands. In: Monteverde Ecology and Conservation of a Tropical Cloud Forest Nadkarni, N. M. Wheelwright, N.T. eds. Oxford University Press, New York, NY, USA pp. 136 137. Otis, Gard W., et al. 1982. Biology and Systematics of the Bee Genus Crawfordapis Colletidae, Diphaglossinea. Psyche 89: 279 296. Roubik, D.W. and Michener, C.D. 1984. Nesting Biology of Crawfordapis luctuosa in Panama Hymenoptera, Colletidae. J. Kansas Ent. Soc. 57: 62 671. Wilson, E.O. 1971. The Insect Societies. Harvard University Press. Cambridge, MA, USA. Wuellner, Clare T. and Jang, Yikweon. 1996. Natural History of a Ground Nesting Solitary Bee, Crawfordapis luctuosa Hymenoptera: Colletidae. Journal of the Kansas Entomological Society. 693: 211 221.
_____________________ ___________________________________________________ FIGURE 1. Mean length of visits with standard error bars shown by C. luctuosa females to nesting holes in a Monteverde cloud forest. Visit length appears to increase with the percentage of holes covered with the exception of day two of zero percent coverage. The effect of day number on the mean length of visit was found to be statistically non significant FisherÂ€s PLSD MD = .459, P = 0.939 _____________________________________________________________________________________ ________________________________________________________________________ FIGURE 2. The mean length of visits w ith standard error bars shown to nest holes by C. luctuosa females when varying percentages of 60 nest holes were covered. Here the visits are not broken down into days. A one way ANOVA test found significant increase in the mean lengths of visits with an increasing percentage of nesting holes covered. _____________________________________________________________________________________
________________________________________________________________________ FIGURE 3. Mean number of long visits with standard error bars shown one minute and over by C. luctuosa females per hole. The effect of the percentage of holes covered on the mean number of long visits was found to be statistically significant between 50% and 25% Fish erÂ€s PLSD post hoc, MD = .612, P = .003, and 50% and zero percent FisherÂ€s PLSD post hoc, MD = .407, P = .044. _____________________________________________________________________________________ ____________________________________________________ ___________________ FIGURE 4. Number of incidents of C. luctuosa females crawling and digging when different percentages of 60 nesting holes in a Monteverde cloud forest were covered. A chi square test found a significant increase in the incidents of diggi ng and crawling activity with an increasing percentage of nesting holes covered. _____________________________________________________________________________________
________________________________________________________________________ FIGURE 5 Crawling and digging behavior exhibited around the covered nest holes of C. luctuosa females in a Monteverde cloud forest. Here the mean length of incidents of crawling and digging are lumped as similar types of hole recovery behavior and the standard erro r shown. FisherÂ€s PLSD post hoc test found the increase in time length spent on hole recovery from 25% to 50% treatment non significant MD = 256.174, P = 511. _____________________________________________________________________________________ ___ _____________________________________________________________________ FIGURE 6. Overall number of incidents of aggression observed between pairs of C. luctuosa bees when varying percentages of 60 nesting holes in a large aggregation were covered and bees b arred entry. A chi square test found a significant increase in the overall incidence of aggression with the increasing amounts of holes covered. _____________________________________________________________________________________
_______________________ _________________________________________________ FIGURE 7. Number of aggressive incidents observed when nests of C. luctuosa females were covered in a Monteverde cloud forest. When the total amount of incidents are divided into categories of those located in the air and those located on ground, a chi square test found that an increasing percentage of holes covered caused a sign ificant increase in air aggression, while the difference was statistically non significant for ground aggression. _____________________________________________________________________________________ ____________________________________________________ ____________________ FIGURE 8. The number of aggressive incidents observed between pairs of C. luctuosa bees was found to increase significantly between the two days of each treatment, although the incidents of aggression decreased on the second day when 5 0% of the 60 nest holes were covered X 2 = 12.362, df = 2, P = .002. _____________________________________________________________________________________