A major area of investigation in evolutionary biology is the evolution of complex traits. The number of states, the order in which they arise, and the number of times a trait has evolved interest evolutionary biologists. Such studies are only made possible by reconstructing phylogenies in the context of the taxa. Biological investigations rely on accurate species designations and delimitations, and lack of well-defined taxonomic groups impedes scientific progress. Pompilidae (Insecta: Hymenoptera), popularly known as spider wasps, are predatory insects that provision their offspring with spiders as the sole food source. Adult female wasps attack spiders and paralyze them with venom, then place them in simple nests that are usually dug in the soil. Spider wasps form a large and cosmopolitan family with nearly 5,000 described species. Although all Pompilidae have similar biology, there is considerable variation in the nest construction and provisioning behavior; thus, this family could be useful for understanding the evolution of complex behavior. My study aims to evaluate and solve several taxonomic conflicts in spider wasps by reconstructing the complex evolution of behavioral patterns using a molecular phylogenetic framework. Early stages of sociality are found in spider wasps, such as communalism (females of same generation nesting together). My ultimate goal was to study the evolution of communalism in these wasps. I reconstructed relationships at the subfamily and tribal levels for the family, as well as generic and specific levels for pre-defined lineages using five nuclear markers (28S, EF, Pol2, LWRh, Wg), one mitochondrial marker (COI), and morphological characters. These studies comprise the first attempt to revise generic, tribal, and species delimitations for spider wasps, based on robust molecular evolutionary trees. Finally, by studying early stages of social evolution, my results will provide for a better understanding the evolution of social behavior in Hymenoptera as a whole.

No description available.

No description available.

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Chapter 1 – General Introduction One of the greatest challenges of ecological research is to predict the response of ecosystems to global change; that is to changes in climate and land use. A complex question in this context is how changing environmental conditions affect ecosystem processes at different levels of communities. To shed light on this issue, I investigate drivers of biodiversity on the level of species richness, functional traits and species interactions in cavity-nesting Hymenoptera. For this purpose, I take advantage of the steep elevational gradient of Mt. Kilimanjaro that shows strong environmental changes on a relatively small spatial scale and thus, provides a good environmental scenario for investigating drivers of diversity. In this thesis, I focus on 1) drivers of species richness at different trophic levels (Chapter 2); 2) seasonal patterns in nest-building activity, life-history traits and ecological rates in three different functional groups and at different elevations (Chapter 3) and 3) changes in cuticular hydrocarbons, pollen composition and microbiomes in Lasioglossum bees caused by climatic variables (Chapter 4). Chapter 2 – Climate and food resources shape species richness and trophic interactions of cavity-nesting Hymenoptera Drivers of species richness have been subject to research for centuries. Temperature, resource availability and top-down regulation as well as the impact of land use are considered to be important factors in determining insect diversity. Yet, the relative importance of each of these factors is unknown. Using trap nests along the elevational gradient of Mt. Kilimanjaro, we tried to disentangle drivers of species richness at different trophic levels. Temperature was the major driver of species richness across trophic levels, with increasing importance of food resources at higher trophic levels in natural antagonists. Parasitism rate was both related to temperature and trophic level, indicating that the relative importance of bottom-up and top-down forces might shift with climate change. Chapter 3 – Seasonal variation in the ecology of tropical cavity-nesting Hymenoptera Natural populations fluctuate with the availability of resources, presence of natural enemies and climatic variations. But tropical mountain seasonality is not yet well investigated. We investigated seasonal patterns in nest-building activity, functional traits and ecological rates in three different insect groups at lower and higher elevations separately. Insects were caught with trap nests which were checked monthly during a 17 months period that included three dry and three rainy seasons. Insects were grouped according to their functional guilds. All groups showed strong seasonality in nest-building activity which was higher and more synchronised among groups at lower elevations. Seasonality in nest building activity of caterpillar-hunting and spider-hunting wasps was linked to climate seasonality while in bees it was strongly linked to the availability of flowers, as well as for the survival rate and sex ratio of bees. Finding adaptations to environmental seasonality might imply that further changes in climatic seasonality by climate change could have an influence on life-history traits of tropical mountain species. Chapter 4 – Cryptic species and hidden ecological interactions of halictine bees along an elevational Gradient Strong environmental gradients such as those occurring along mountain slopes are challenging for species. In this context, hidden adaptations or interactions have rarely been considered. We used bees of the genus Lasioglossum as model organisms because Lasioglossum is the only bee genus occurring with a distribution across the entire elevational gradient at Mt. Kilimanjaro. We asked if and how (a) cuticular hydrocarbons (CHC), which act as a desiccation barrier, change in composition and chain length along with changes in temperature and humidity (b), Lasioglossum bees change their pollen diet with changing resource availability, (c) gut microbiota change with pollen diet and climatic conditions, and surface microbiota change with CHC and climatic conditions, respectively, and if changes are rather influenced by turnover in Lasioglossum species along the elevational gradient. We found physiological adaptations with climate in CHC as well as changes in communities with regard to pollen diet and microbiota, which also correlated with each other. These results suggest that complex interactions and feedbacks among abiotic and biotic conditions determine the species composition in a community. Chapter 5 – General Discussion Abiotic and biotic factors drove species diversity, traits and interactions and they worked differently depending on the functional group that has been studied, and whether spatial or temporal units were considered. It is therefore likely, that in the light of global change, different species, traits and interactions will be affected differently. Furthermore, increasing land use intensity could have additional or interacting effects with climate change on biodiversity, even though the potential land-use effects at Mt. Kilimanjaro are still low and not impairing cavity-nesting Hymenoptera so far. Further studies should address species networks which might reveal more sensitive changes. For that purpose, trap nests provide a good model system to investigate effects of global change on multiple trophic levels and may also reveal direct effects of climate change on entire life-history traits when established under different microclimatic conditions. The non-uniform effects of abiotic and biotic conditions on multiple aspects of biodiversity revealed with this study also highlight that evaluating different aspects of biodiversity can give a more comprehensive picture than single observations. / Kapitel 1 – Allgemeine Einführung Eine der größten Herausforderungen der ökologischen Forschung ist es, die Reaktion der Ökosysteme auf den globalen Wandel, d.h. auf Veränderungen von Klima und Landnutzung, vorherzusagen. Eine komplexe Frage in diesem Zusammenhang ist, wie sich verändernde Umweltbedingungen auf die Ökosystemprozesse auf verschiedenen Ebenen von Gemeinschaften auswirken. Um dieses Thema näher zu beleuchten, untersuche ich die Triebkräfte der Biodiversität auf der Ebene des Artenreichtums, der funktionellen Eigenschaften und der Wechselwirkungen zwischen Arten bei Hautflüglern, die in Hohlräumen nisten. Zu diesem Zweck nutze ich den steilen Höhengradienten des Kilimandscharo, der starke Umweltveränderungen auf relativ kleinem Raum mit sich bringt und somit ein gutes System für die Untersuchung von Triebkräften der biologischen Vielfalt bietet. In dieser Arbeit konzentriere ich mich auf 1) Triebkräfte des Artenreichtums auf verschiedenen trophischen Ebenen (Kapitel 2); 2) saisonale Muster in der Nestbauaktivität, lebensgeschichtliche Merkmale und ökologische Raten in drei verschiedenen funktionellen Gruppen und in verschiedenen Höhenlagen (Kapitel 3) und 3) Veränderungen in kutikulären Kohlenwasserstoffen, Pollenzusammensetzung und Mikrobiomen bei Lasioglossum Bienen, die durch klimatische Faktoren verursacht werden (Kapitel 4). Kapitel 2 – Klima und Nahrungsressourcen prägen den Artenreichtum und die trophischen Wechselwirkungen von hohlraumnistenden Hautflüglern Die Triebkräfte des Artenreichtums werden seit Jahrhunderten erforscht. Temperatur, Ressourcenverfügbarkeit und Top-Down-Regulierung sowie die Auswirkungen der Landnutzung werden als wichtige Faktoren für die Bestimmung der Insektenvielfalt angesehen. Die relative Bedeutung jedes dieser Faktoren ist jedoch unbekannt. Mit Hilfe von Nisthilfen entlang des Höhengradienten des Kilimandscharo versuchten wir, die Triebkräfte des Artenreichtums auf verschiedenen trophischen Ebenen zu enträtseln. Die Temperatur war der Hauptfaktor für den Artenreichtum auf allen trophischen Ebenen, wobei die Bedeutung der Nahrungsressourcen auf den höheren trophischen Ebenen der natürlichen Antagonisten zunahm. Die Parasitierungsrate wurde sowohl durch die Temperatur als auch durch die trophische Ebene bestimmt, was darauf hindeutet, dass sich die relative Bedeutung der Bottom-up- und Top-down-Kräfte mit dem Klimawandel verschieben könnte. Kapitel 3 – Saisonale Schwankungen in der Ökologie von tropischen hohlraumnistenden Hautflüglern Natürliche Populationen schwanken mit der Verfügbarkeit von Ressourcen, dem Vorhandensein natürlicher Feinde und klimatischen Schwankungen. Die Saisonalität ist jedoch auf tropischen Bergen noch nicht gut untersucht. Wir untersuchten saisonale Muster in der Nestbauaktivität, funktionale Merkmale und ökologische Raten bei drei verschiedenen Insektengruppen in niedrigeren und höheren Höhenlagen. Insekten wurden mit Nisthilfen gefangen, die während eines Zeitraums von 17 Monaten, der drei Trocken- und drei Regenzeiten umfasste, monatlich überprüft wurden. Die Insekten wurden nach ihren funktionalen Gilden eingeteilt. Alle Gruppen zeigten eine starke Saisonalität im Nestbau, die in niedrigeren Lagen höher war und dort zwischen den Gruppen stärker synchronisiert war. Die Saisonalität im Nestbau von Raupen- und Spinnen- jagenden Wespen war mit saisonalen Klimaschwankungen verbunden, während sie bei Bienen stark von der Verfügbarkeit von Blüten abhing, genauso wie die Überlebensrate und das Geschlechterverhältnis der Bienen von der Blütenmenge abhing. Die Anpassung an die Saisonalität der Umwelt könnte bedeuten, dass weitere Veränderungen der saisonalen Klimaschwankungen durch den Klimawandel einen Einfluss auf die lebensgeschichtlichen Merkmale tropischer Bergarten haben könnten. Kapitel 4 – Kryptische Arten und versteckte ökologische Wechselwirkungen bei Schmalbienen entlang eines Höhengradienten Starke Umweltgradienten, wie sie an Berghängen auftreten, stellen für Arten eine Herausforderung dar. Versteckte Anpassungen oder Interaktionen wurden in diesem Zusammenhang selten berücksichtigt. Als Modellorganismen haben wir Bienen der Gattung Lasioglossum verwendet, da Lasioglossum die einzige Bienengattung ist, die über den gesamten Höhengradienten am Kilimandscharo weit verbreitet ist. Wir fragten, ob und wie (a) kutikuläre Kohlenwasserstoffe (CHC), die als Barriere gegen Austrocknung wirken, sich in ihrer Zusammensetzung und Kettenlänge entlang von Temperatur- und Feuchtigkeitsänderungen verändern; (b) Lasioglossum Bienen ihre Pollennahrung mit wechselnder Ressourcenverfügbarkeit ändern; (c) Änderungen von Darm-Mikrobiota mit Pollennahrung und Klimabedingungen und Änderungen von Oberflächen-Mikrobiota mit CHC und Klimabedingungen zusammen hängen, und ob die Veränderungen eher durch den Wechsel von Lasioglossum Arten entlang des Höhengradienten beeinflusst werden. Wir fanden physiologische Anpassungen an das Klima in CHC, sowie Veränderungen in der Zusammensetzung von Pollennahrung und Mikrobiota, die auch miteinander korrelierten. Diese Ergebnisse deuten darauf hin, dass komplexe Wechselwirkungen und Rückkopplungen zwischen abiotischen und biotischen Bedingungen die Artenzusammensetzung in einer Gemeinschaft bestimmen. Kapitel 5 – Allgemeine Diskussion Abiotische und biotische Faktoren förderten die Artenvielfalt, Eigenschaften und Wechselwirkungen von Arten und sie wirkten unterschiedlich, je nachdem, welche funktionelle Gruppe untersucht wurde und ob räumliche oder zeitliche Einheiten berücksichtigt worden sind. Es ist daher wahrscheinlich, dass im Lichte des globalen Wandels verschiedene Arten, Merkmale und Wechselwirkungen unterschiedlich betroffen sein werden. Darüber hinaus könnte eine zunehmende Landnutzungsintensität zusätzliche Auswirkungen oder Wechselwirkungen mit dem Klimawandel auf die Biodiversität haben, auch wenn die potenziellen Landnutzungseffekte am Kilimandscharo noch gering sind und bis jetzt die hohlraumnistenden Hautflüglern nicht beeinträchtigen. Weitere Studien sollten sich mit Nahrungsnetzwerken befassen, die empfindlichere Veränderungen aufzeigen könnten. Nisthilfen bieten dafür ein gutes Modellsystem, um die Auswirkungen des globalen Wandels auf mehreren trophischen Ebenen zu untersuchen, und können auch direkte Auswirkungen des Klimawandels auf ganze lebensgeschichtliche Merkmale aufzeigen, wenn sie unter verschiedenen mikroklimatischen Bedingungen etabliert werden. Die nicht einheitlichen Auswirkungen abiotischer und biotischer Bedingungen auf mehrere Aspekte der Biodiversität, die in dieser Studie gezeigt wurden, zeigen auch, dass die Untersuchung verschiedener Aspekte der Biodiversität ein umfassenderes Bild vermitteln kann als Einzelbetrachtungen.

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The Vespidae family (order Hymenoptera) is comprised of 4500 species of wasps in 268 genera and 7 subfamilies. These wasps prey upon a wide range of insects, including Lepidopteran caterpillars. Because of their low prey specificity, the use of Vespid wasps in biological control programs is limited. However, in their natural habitat, they play a role in controlling populations of some pest species. This study was conducted in six different communities in the department of La Paz within the municipalities of Coroico and Coripata. Three ecological niches were selected in each community: 1) the forest, 2) the edge of the forest and 3) a crop producing area. In each study unit, three Malaise traps were set up on a 14 day collection cycle from June to December 2007. Over the six month study period, we collected a total of 772 individuals and identified 36 different morphospecies from the six communities. The most abundant genera collected were Protopolybia sp., Mischocyttarus sp., and an unidentified genus (morphospecies #2) which had the greatest abundance of individuals in all of the different ecological niches. The niche factor did not have a significant influence on species diversity in the three ecological niches studied. Generally, this group of wasps is found in all three ecological niches.

In societies where all individuals are reproductively totipotent and yet, at a given time only one of them reproduces, it is interesting to examine the factor(s) that may influence and predict who will be the reproductive. I am investigating various behavioural, morphological and physiological parameters in the primitively eusocial wasp Ropalidia marginata, and their role in determining the current reproductive and her future successors. In several group-living species, especially in primitively eusocial ones, a strong link between behavioural dominance and reproductive dominance is observed. Hence, I am also investigating the possible determinants of behavioural dominance in R. marginata. I have carried out my study on artificially constituted pairs of wasps as well as in natural colonies in laboratory cages, which represent the founding phase and the established phase in the colony cycle, respectively. Chapter 1: Behavioural and Reproductive Dominance in Pairs of R. marginata Age and body size had no effect on behavioural dominance in pairs of R. marginata, whereas prior experience of behavioural dominance affected future dominance status, indicating presence of winner- and loser-effects. Dominance ranks are relatively stable. This is different from what has been found in colonies, where dominance ranks sometimes change on a daily basis. Body size had no effect, whereas age and behavioural dominance had a significant effect on reproductive dominance in pairs, with older individuals and more dominant individuals having a higher probability of becoming the reproductive. Since no relationship was found between age and behavioural dominance, we predict that the underlying mechanisms by which age and behavioural dominance affect reproductive dominance and independent of each other. This study gives a clear indication that age and behavioural dominance are important variables that determine the reproductive individual during the founding phase of the colony. Chapter 2: Comparison of Dominance Indices and Recommendations for their Use When several individuals interact with each other as in colonies, in a differential and sometimes in a preferential manner, it is difficult to attribute dominance ranks to individuals. Dominance indices are employed to simplify these interactions and rank individuals in dominance hierarchies. Since the rationale behind using a particular dominance index is seldom given in behavioural literature, a comparison of three dominance indices was carried out in second part of the thesis. Each index was gauged on how similar are its ranks as compared to other two indices. Indices were also compared based on the number of untied or unique ranks they attributed. The index that gave least number of ties in ranks was assumed to be better than others. In addition to data from R. marginata colonies, I used data from R. cyathiformis colonies (a congeneric species which behaves more like a typical primitively eusocial species), and artificial data sets, to increase variability in the interaction patterns. We found that each of the indices had their own advantages and disadvantages. In species like R. marginata and R. cyathiformis, where only a few pairs show interactions, and among those who do, very few show reversals, Frequency-based Dominance Index (FDI) is the recommended index of choice. Studies like these will help in understanding how dominance indices operate under certain situations before applying them to construct hierarchies. Chapter 3: Behavioural and Reproductive Dominance in Colonies of R. marginata Age does not affect behavioural dominance, whereas winner and loser effects exist in colonies of R. marginata, just as in pairs. When analysed in detail, I found that colonies of R. marginata showed fewer proportion of pairs interacting, and lower frequency/hour/pair of dominance-subordinate interactions as compared to experimentally paired individuals (from 1st chapter). However, the dominance displays and behaviours were much more intense and severe in colonies. After dominance hierarchies are already established in colonies, frequent need to show dominance behaviour may not arise, due to familiarity between interacting individuals. However, since individuals are possibly aware of each others’ strengths due to past interactions, dominance behaviours are much more severe when contests do happen. My results show that there might be some similarities in terms of determinants of behavioural dominance between pairs and colonies, but the expression of behavioural dominance is quite different. From earlier work it was already known that if the queen/reproductive of the colony disappears or is experimentally removed, one of the individuals shows extreme levels of aggression. This individual, referred to as the potential queen (PQ), will go on to become the next queen of the colony. Her behavioural profile, from the emergence till she establishes herself as the next queen have been well studied earlier. What was not known were the factor(s) that determine the identity of the PQ. It was also unclear what happens when the queen as well as the PQ are both removed, simultaneously or in quick succession. To test whether there is a longer reproductive hierarchy in R. marginata, the queen and the first potential queen of a nest were removed. I found that successive potential queens emerged as readily as the first potential queen, and with dominance profiles comparable to the first PQ, indicating that a reproductive hierarchy indeed exists, at least up to five PQ’s. It was also found that these potential queens were acceptable to all other individuals, as there was not a single act of behavioural dominance directed toward any potential queen. It was also observed that all PQs went on to become queens if the previous queen or PQ was not returned. When tested for various morphological, physiological, behavioural and life history traits (factors possibly influencing the position of an individual in the reproductive hierarchy), we found that age is the only variable that emerges as an important predictor of reproductive succession, with older animals having a higher chance to succeed as next queens of the colony, although even age is not an absolute predictor. Unlike in the pairs, in colonies of R. marginata behavioural dominance is not a good predictor of an individual’s ability to be the queen or the potential queens. The four most important findings of my study are: (i) the first demonstration of winner and loser effects in social insects; (ii) the demonstration that behavioural dominance influences reproductive dominance in pairs but not in colonies; (iii) demonstration of a long reproductive queue among individuals of a colony; and (iv) discovering that age is an important predictor of the identity of the queen and the future queens of the colony. I believe these findings will add significantly to our growing knowledge of the social biology of R. marginata. Finally, my work shows that pairs of R. marginata, representing the founding phase of the colony, behave more like a typical primitively eusocial species, whereas colonies which represent the established phase of the colony cycle behave more like highly eusocial species. Finding the characters of two different forms of sociality in the same species in different phases of the colony cycle makes R. marginata an excellent model system to study evolution of eusociality.

Ropalidia marginata is characterized as a primitively eusocial wasp due to the absence of morphological differentiation between the queen and worker castes. Unlike other primitively eusocial wasps, however, the queen in this species is a docile individual, who does not use aggression to regulate worker reproduction, and does not act as the central pacemaker of her colony. However, if the queen dies or is experimentally removed, one of the workers steps up her aggression immensely within minutes, and if the queen is not replaced, she develops her ovaries, reduces aggression and takes over as the new queen of the colony. We call her the potential queen (PQ). When I started my work on R. marginata, two very intriguing questions were demanding to be answered, which had developed from work done by my immediate seniors in the lab. I decided to pursue both of these for my thesis. My work has been enriched by inputs from several collaborators and colleagues - I couldn’t have done all of it by myself. So, henceforth, I will be using the word “we”, instead of the first person singular to describe the work that has gone into this thesis. Question 1: Is there a designated successor to the queen in R. marginata? My senior Sujata P. Kardile has shown in her thesis, that in R. cyathiformis, a primitively eusocial wasp very closely related to R. marginata, the queen is always succeeded by the next most aggressive individual in the colony, and so the PQ is easily predictable in the presence of the queen. However, in R. marginata, the PQ appears to be an unspecialized individual, who cannot be predicted in the presence of the queen by using age, ovarian profile or behaviour as the yardsticks. However, the PQ becomes evident within minutes after queen removal. The swiftness with which the PQ is established led us to believe that perhaps the successor to the queen in R. marginata is known to the wasps, though we cannot identify her in the presence of the queen. We designed an experiment to check for the presence of such a ”cryptic successor” in R. marginata. Our experiments involved splitting a normal, queen-right nest into two halves separated by a wire mesh partition, so that the wasps could not move across the mesh. Earlier we had used this set-up to demonstrate that a PQ always establishes herself on the queen-less fragment of the nest. So, to test if there is a cryptic successor, we allowed a PQ to establish herself on the queen-less fragment, and then exchanged the queen and the PQ (designated as PQ1) between the two sides. There is a 50% probability that the cryptic successor, if present, would be on the queen-less side in the beginning. Then, upon exchange, she should be able to hold her position on the other side easily. On the other hand, if the cryptic successor is first on the queen-right side, then, upon exchange, she should take over as the PQ (PQ2), and PQ1 should not be able to hold her status. The cryptic successor hypothesis had two predictions: (i) the PQ1 would lose to a PQ2 in about half the cases, and (ii) there would never be a PQ3. We obtained a PQ2 in 5 out of 8 cases, and we never had a PQ3. So we could conclude that there is indeed one individual who is the designated successor to the queen in R. marginata. Since we could not identify her in the presence of the queen, we call her the cryptic successor. The cryptic successor did not receive even a single act of aggression from the PQ1, or from any other individual in the colony. Thus we conclude that she is acceptable to all the wasps in the colony. We next used the more sophisticated and rigorous method of network analysis to check if the PQ could be predicted due to some unique position she might be holding in the social network on her colony. Since this was a first study in a primitively eusocial insect using network tools, we began by characterizing the social networks of queen-right and queen-less colonies of R. marginata, and compared them with the R. cyathiformis networks to see how different the R. marginata society is from a typical primitively eusocial one. The R. marginata social networks based on dominant-subordinate interactions were low in their centrality measure as compared to the R. cyathiformis networks. However, in both the species, the queen-less networks were highly centralized, star-shaped networks with the PQs at the centre. Neither the queens, nor the PQs were key individuals in the queen-right colonies, but it is interesting to note that the removal of an insignificant node, the queen, resulted in a major change in the network architecture, converting the de-centralized queen-right network into a highly centralized one. Such centralized star-shaped networks are unique, and to our knowledge, the first ever described, in any social system. When we removed the queen from the data set (in silico removal), the resulting network was similar in centrality to the queen-right networks. We then did a comparative analysis of the positional importance of the PQs of the two species, and tried to see if we could use this as a tool to predict the PQ in the queen-right network. In R. cyathiformis, the PQs had consistently high ranks (mostly rank 2) in the network based on the degree index, while the PQs in R. marginata had random ranks in the hierarchy. However, since the PQs are known not to have unique ranks in the dominance hierarchies, we repeated the analysis using data on all interactions from the Q-PQ exchange experiments described above. Neither the cryptic successors nor the losers occupied any unique ranks in the all interactions networks. Thus the successors in R. marginata are truly cryptic, even in their social networks. Since R. marginata is known to be more evolved than typical primitively eusocial species, it is likely that the queen’s successor is identified by the wasps through some subtle cue like smell, and so we cannot identify her using the methods that are adequate for the identification of the PQ in a typical primitively eusocial species like R. cyathiformis. Question 2: How does the queen signal her presence and reproductive status to her workers or, how do the workers perceive the presence of their queen? The fact that in spite of her docility, the queen in R. marginata manages to maintain complete reproductive monopoly in her colony, gives rise to the obvious question of how she suppresses worker reproduction. The most attractive hypothesis is that she uses a pheromone like queens of highly eusocial species. My senior A. Sumana had shown that the queen pheromone, if present, is not a volatile substance. She also showed that the queen interacts at a very low rate with her workers, and so they cannot possibly perceive her by means of direct interactions. Since the PQ steps up her aggression within minutes of queen removal, we used her as a proxy to know how soon the queen’s absence is felt in the colony. We built a model to delineate the relationship between the decay time of the pheromone (td), the average age of the queen’s signal present with the PQ (ta), and the average realization time (tr); where tr = td − ta. Using Dijkstra’s algorithm, we showed that the queen could interact faster with the PQ by using relay interactions. Then using experimental data from 50 colonies, we obtained a ta of 102.9 minutes. The td was 340 minutes, and so we obtained a tr of 237.1 minutes; which meant that the PQ should not perceive the queen’s absence within 237 minutes of queen removal, if the queen pheromone is transmitted by a relay mechanism. However, from our experimental data, we had obtained a tr of 30 minutes. So we concluded that physical interactions, both direct and indirect were inadequate for the workers to perceive their queen. As we had ruled out physical interactions, we then wanted to check if it is possible that the queen applies her pheromone to the nest material, from where it is perceived by the workers when they walk or sit on the nest, or antennate the nest surface. The “rub abdomen behaviour (RA)” has been observed to be quite typical of R. marginata queens, and is not very common in the workers of the species. RA involves rubbing the ventral side of the tip of the abdomen or dragging it on the nest surface while walking. We thought that the queen might be using this behaviour to apply her pheromone on the nest material. So we characterized this behaviour using focal behaviour sampling, and found that the queen rubs her abdomen on the nest once in every 23 minutes. Since the observed tr is 30 minutes, it is quite likely that the queen uses the rub abdomen behaviour to apply her pheromone on the nest. The next step was to check for the source of the queen pheromone. We looked for glands that open near the base of the sting, and the Dufour’s gland was a good choice, as it is known to be involved in the recognition of egg-laying workers in the honeybees. We performed a bioassay in the blind using the crude extract of the Dufour’s gland (prepared in Ringer’s solution) from the queen. The Dufour’s gland extract of a randomly chosen worker and the solvent were used as controls. We found that the PQ responds to the queen’s Dufour’s gland extract by lowering her aggression to 65% of what she was showing on queen removal and before the application of the extract. However, the PQ did not change her behaviour significantly when the worker’s extract or Ringer’s solution was applied. The PQ’s reduction of aggression on application of the queen’s extract mimicked the reaction of PQ’s when the queen is re-introduced on the nest some time after removal. So we hypothesize that the Dufour’s gland is the source of the queen pheromone (signal) in R. marginata. This thesis has opened up newer questions pertaining to the power of the queen and the intricacies of the succession to power in R. marginata. For example, we need to pursue chemical analyses of the Dufour’s gland extract of R. marginata to have conclusive proof of it’s being the source of the queen pheromone. But that is perhaps suitable topic for my juniors in the lab, who can continue the tradition of beginning with questions opened up by their seniors!

Parasitic insects are known for their distinct life strategy: they necessarily kill their hosts in order to complete their life cycle. Eighty percent of parasitoids species belongs to the order Hymenoptera (bees, ants and wasps). Among parasitoid wasps Ichneumonidae stands out with more than 25 thousand species and a great diversity of habits and hosts. Despite the large number of species already described, there is a low representativeness of species in tropical regions, mainly due to the lack of taxonomical studies in those areas. The objective of the present study was to compile the information on the biology of Ichneumonidae through an extensive literature review and to conduct a taxonomic study of the species of Charops Holmgren, 1859 (Campopleginae) occurring in Brazil. It was observed that out of the 950 species of Ichneumonidae registered in Brazil, less than 10% present some host records. These records are mainly concentrated in the south and southeast of the Brazil where the relatively largest number of taxonomists are concentrated. In addition, most of the records relate to hosts of economic importance in corn, soybean and cotton crops. Little is known about the parasitoid / host interaction in natural Brazilian biomes. Also, thirty-three species with dubious occurrence in Brazil were found. Notwithstanding Campopleginae being one of the subfamilies with the highest number of host records, taxonomical studies on it are still scarce in Brazil. An example is the genus Charops, which despite having recorded for Brazil at genus level, has never been studied through a taxonomic point of view. The study of 614 specimens of this genus revealed 9 new species from Brazil, being the first described for South America. Its geographical distribution record is expanded and illustrated in distribution maps. High resolution images and a key for these species are also provided. / Insetos parasitoides são conhecidos pela sua distinta estratégia de vida, na qual para concluir o seu ciclo de vida necessariamente matam os seus hospedeiros. Oitenta por cento das espécies de parasitoides pertencem à ordem Hymenoptera (abelhas, formigas e vespas). Dentre as vespas parasitoides destaca-se a família Ichneumonidae, que possui mais de 25 mil espécies nominais e apresenta grande diversidade de hábitos e hospedeiros. Apesar do grande número de espécies já descritas, existe uma baixa representatividade de espécies conhecidas de regiões tropicais devido, principalmente, à escassez de estudos taxonômicos na região. O presente estudo teve por objetivo compilar as informações sobre a biologia de Ichneumonidae a partir de uma extensa revisão da literatura e realizar um estudo taxonômico das espécies de Charops Holmgren, 1859 (Campopleginae) que ocorrem no Brasil. Foi observado que cerca das 950 espécies de Ichneumonidae que ocorrem no Brasil, menos de 10% possuem algum registro de hospedeiro. Tais registros estão concentrados principalmente nas regiões sul e sudeste do Brasil aonde se concentra a maior quantidade de taxonomistas do país. Além disso, grande parte dos registros referem-se a hospedeiros de importância econômica nas culturas de milho, soja e algodão. Pouco se sabe sobre a interação entre parasitoides/hospedeiros em biomas naturais brasileiros. Foram encontradas 33 espécies que apresentam registro de ocorrência dúbio para o Brasil. Apesar de ser uma das subfamílias com maior número de registros de hospedeiro, Campopleginae permanece relativamente carente de estudos taxonômicos no Brasil. Um exemplo disso é o gênero Charops que apesar de apresentar registros para o Brasil (em nível de gênero), nunca foi estudado através de um viés taxonômico. O estudo de 614 exemplares deste gênero revelou 9 espécies novas para o Brasil, sendo estas as primeiras espécies descritas para a América do Sul. Sua distribuição geográfica conhecida foi ampliada e ilustrada em mapas de distribuição. Imagens de alta resolução e uma chave de identificação para essas espécies são fornecidas.