Nest architecture of the leaf-cutting ant <Emphasis Type="Italic">Acromyrmex rugosus rugosus</Emphasis>

The prominent nests mounds of many ant species are one of the most obvious signs of their presence, yet the subterranean architecture of nests is often poorly known. The present work aimed to establish the external and internal structure of nests of a species of leaf-cutting ant, Acromyrmex rugosus rugosus, by either marking the interior of nests with talcum powder, or forming casts with cement. Twelve nests were excavated and surveyed, with eight being marked with talcum powder and four cast with cement. The external and internal structure of the nests was highly variable. The largest and smallest nests had mound areas of 9.89 m² and 0.01 m² respectively. The number of chambers found ranged from 1 to 26, with maximum dimensions of between 6 and 70 cm. Chambers were found close to the soil surface (6 cm) down to a maximum depth of 3.75 m. In addition to chambers containing fungus garden, some chambers were found to be empty, filled with soil or filled with waste, the first time this has been recorded in a species of Acromyrmex. The nests of A. rugosus rugosus appear to be unusually complex for the genus, containing a diversity of irregular chambers and tunnels. Received 21 December 2006; revised 30 May 2007; accepted 1 June 2007.     

The New World oil‐collecting bees Centris and Epicharis (Hymenoptera,Apidae): molecular phylogeny and biogeographic history

We present a first comprehensive time‐calibrated phylogeny for two Neotropical genera of bees, Centris and Epicharis, whose females collect floral oil together with pollen for larval provisioning, and that traditionally have been grouped in the tribe Centridini. Our analyses rely on a matrix of 167 taxa and 4228 aligned nucleotides for the subfamily Apinae, with denser sample of Centris and Epicharis. Centris and Epicharis are strongly supported monophyletic groups, but Centridini is paraphyletic in relation to the corbiculate bees. The inner phylogenetic relationships of Epicharis agree with the current taxonomic classification. In Centris, three main clades were recovered, namely the Centris, Trachina and Melacentris groups. Inner relationships in Centris suggest the reinstatement of some subgenera and proposition of new ones. Early diversification of Centris and Epicharis took place at the tropical regions of South America. Epicharis and the Melacentris group in Centris mostly diversified in that region, expanding over Central America and tropical North America only recently in the last 3 My. The groups Trachina and Centris present a complex biogeographic history, with expansions to the Nearctic region, the Antilles, and temperate regions of South America in the late Oligocene and Miocene.     

Floral Lipid Chemistry of Byrsonima crassifolia (Malpigheaceae) and a Use of Floral Lipids by Centris Bees (Hymenoptera: Apidae)

Byrsonima rrassifolia (L.), a Neotropical malpighiaceous tree or treelet, has flowers that produce abundant lipids instead of nectar. Several species of Centris bees collect this oil. The floral oil shows variation between trees and can be separated into two types. One type is most common (11 of 14 samples) and consists of mono- and di-glycerides, some free fatty acids, a small amount of tri-glycerides and a trace of carbohydrate. The composition of the glycerides is predominantly (53–63%) esters of unsaturated 18C–22C fatty acids with the rest made up of 14C–18C saturated fatty acids. The second type of floral oil is similar to type one except that the samples contain large amounts of an unknown lipid more polar than the standards. Oil collected from the scopae of two representative Centris species, C. adanae and C. flavofasciata, was the same as the type one oil collected from B. rrassifolia floral elaiophores. The liquid provisions from the cells of several groundnesting Centris species was also found to be identical to B. crassifolia type one floral elaiophore oil with the exception of several minor ninhydrin positive compounds which may have been derived from the pollen which makes up part of the larval food provisions.     

Centris pallida (Hymenoptera: Apidae) male body size decreases across five decades

Historical data suggest that many bee species have declined in body size. Larger-bodied bees with narrow phenological and dietary breadth are most prone to declines in body size over time. This may be especially true in solitary, desert-adapted species that are vulnerable to climate change such as Centris pallida (Hymenoptera: Apidae). In addition, body size changes in species with size-linked behaviours could threaten the prevalence of certain behavioural phenotypes long-term. C. pallida solitary bees are found in the Sonoran Desert. Males use alternative reproductive tactics (ARTs) and are dimorphic in both morphology and behaviour. C. pallida male body size has been studied since the 1970s in the same population. The authors collected body size data in 2022 and combined it with published records from 1974–2022. The authors find a persistent decline in the mean head width of patrolling males, and shifts towards smaller body sizes in the populations of males found foraging and hovering. Both morphs declined in average body size, and the proportion of large-morph males in the population decreased by 8%. Mating males did not decline in mean body size over the last five decades. The authors discuss hypotheses related to the decline in C. pallida male head width. Finally, the authors advocate for C. pallida as an excellent study system for understanding the stability of ARTs with size-linked behavioural phenotypes.     

Directional selection by the subterranean termite Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) at tunnel intersections

Subterranean termites construct complicated tunnel networks for foraging below ground. Thus, they often encounter tunnel intersections during foraging activity. Directional selection by termites at intersections is likely to affect foraging efficiency because depending on their selection, the path length from food resources to the nest can vary significantly. In order to understand how termites are guided to choose the most economical path without the use of pheromones, we artificially excavated two tunnels of varying widths (W₁ and W₂; 2, 3, or 4 mm) that intersected at a 90° angle in each of nine soil‐filled arenas. We observed the directional selection of termites at intersections in arenas with combinations of W₁ (mm) and W₂ (mm) (W₁, W₂). For (W₁, W₂) = (2, 2) and (4, 4), termites statistically equally chose the three directions left, right, and straight, while for the (3, 3) arena combination, termites preferentially decided to go straight. On the other hand, for (W₁, W₂) = (2, 3) (2, 4), and (3, 4), termites advancing from narrower tunnels into intersections tended to turn right or left, while termites coming from the wider tunnel were more inclined to go straight. On the assumption that a wider tunnel is more frequently used by termites in the field, we can deduce that the wider tunnel may represent the most efficient/shortest path. Thus, this simple selection mechanism can prevent termites from deviating from the most economical path.     

Macroscopic and microscopic studies of the nests and the stages involved in the nesting process of <Emphasis Type="Italic">Centris muralis</Emphasis> Burmeister (Hymenoptera: Apidae: Centridini) bee in the adobe walls,in La Rioja,Argentina

Centris (Wagenknechtia) muralis Burmeister is one of the most common bee species distributed in the xeric region of Argentina. This work describes macro-and micromorphological aspects of the nesting architecture and the stages involved in the process of nesting of C. muralis bee, in the adobe walls of Capayán ruins and recent earthen constructions in Udpinango and Villa Castelli, La Rioja, Argentina. In addition, we discuss the possible factors that may explain the high density of nests observed in the adobe walls of Capayán ruins. These constructions are settled in the northern area of the Monte desert. Our analysis showed that the nest cell walls are strengthened and waterproofed probably by the admixture of organic material to the adobe matrix. Light microscopy of thin sections of the vacated cells showed the inner layers of organic material corresponding to the cocoon, and the outer layer of 0.7 mm thick corresponding to the cell walls consisting mainly of silt and clay, fine sand grains in low rate and absence of grains of sand medium and large. The cell wall was not different in its granulometry from that in the adobe brick, thus suggesting that the cell wall was constructed probably by cementing the particles with bee secretion. The scanning micrographs showed that the cell walls and non-nesting zones exhibited abundant clay crystals in the grain distribution. Pollen from Larrea sp. was observed in high proportions in the nest contents of C. muralis in the Capayán adobe walls.     

Influence of Guidelines and Passageways on Tunneling Behavior of Reticulitermes flavipes (Kollar) and R. virginicus (Banks) (Isoptera: Rhinotermitidae)

Tunneling behavior of laboratory-maintained cultures of Reticulitermes flavipes (Kollar) and R. virginicus (Banks) was examined to determine (1) if the termites build tunnels along preexisting wires or tunnels, and (2) whether tunnels are arranged to optimize search efficiency. Tunnel patterns were considered optimal if, for the number of tunnels present, the maximum area was explored. Termites entered either control arenas or arenas in which they encountered a wire or a pre-formed tunnel. Analyses revealed that R. flavipes and R. virginicus almost always follow pre-formed tunnels, but do not follow wires as readily. Within each species, the distributions of tunnels in treatment arenas were different from distributions in control arenas, most often when pre-formed tunnels were the treatment. Optimal tunnel arrangements in control arenas were found in 62% of R. flavipes patterns with 2 tunnels and in 43% of R. virginicus patterns with 2 tunnels. None of the 3-tunnel patterns from control arenas of R. flavipes and 29% of those of R. virginicus had optimal arrangements. Overall, the spatial arrangement of tunnels in control arenas was significantly different between R. flavipes and R. virginicus.     

Nest-building and communal care of young byTilapia rendalli dumeril (pisces,cichlidae) in Lake Malawi

Synopsis Tilapia rendalli of Lake Malawi dig large tunnels in their nests and practise communal care of young. Both these traits are considered to be antipredator adaptations.     

Soil temperature, digging behaviour, and the adaptive value of nest depth in South American species of Acromyrmex leaf-cutting ants

In leaf-cutting ants, workers are expected to excavate the nest at a soil depth that provides suitable temperatures, since the symbiotic fungus cultivated inside nest chambers is highly dependent on temperature for proper growth. We hypothesize that the different nesting habits observed in Acromyrmex leaf-cutting ants in the South American continent, i.e. superficial and subterranean nests, depend on the occurrence, across the soil profile, of the temperature range preferred by workers for digging. To test this hypothesis, we first explored whether the nesting habits in the genus Acromyrmex are correlated with the prevailing soil temperature regimes at the reported nest locations. Second, we experimentally investigated whether Acromyrmex workers engaged in digging use soil temperature as a cue to decide where to excavate the nest. A bibliographic survey of nesting habits of 21 South American Acromyrmex species indicated that nesting habits are correlated with the soil temperature regimes: the warmer the soil at the nesting site, the higher the number of species inhabiting subterranean nests, as compared to superficial nests. For those species showing nesting plasticity, subterranean nests occurred in hot soils, and superficial nests in cold ones. Experimental results indicated that Acromyrmex lundi workers use soil temperature as an orientation cue to decide where to start digging, and respond to rising and falling soil temperatures by moving to alternative digging places, or by stopping digging, respectively. The soil temperature range preferred for digging, between 20°C and maximally 30.6°C, matched the range at which colony growth would be maximized. It is suggested that temperature-sensitive digging guides digging workers towards their preferred range of soil temperature. Workers’ thermopreferences lead to a concentration of digging activity at the soil layers where the preferred range occurs, and therefore, to the construction of superficial nests in cold soils, and subterranean ones in hot soils. The adaptive value of the temperature-related nesting habits, and the temperature-sensitive digging, is further discussed.     

Nest-moving by the polydomous ant <Emphasis Type="Italic">Cataglyphis iberica</Emphasis>

In this paper we analyze emigration from nests by the polydomous ant Cataglyphis iberica. Social carrying of workers of this species between different nests of the colony is frequent. In Bellaterra (Barcelona, NE Spain), we monitored field emigration of C. iberica by noting for each nest the migratory behavior of C. iberica workers and, when the nests were attacked by another ant species, Camponotus foreli, we noted the number of C. foreli workers involved in the attacks. Emigration of C. iberica from nests was highly variable. We suggest the main factor determining emigration by this species was attack by workers of C. foreli, so emigration from C. iberica nests was much faster when harassment by C. foreli increased. The system of multiple nests of C. iberica enables this species to abandon attacked nests and to reinstall their population in other nests of the same colony. This reduces risk to the colonies because the route between the different nests is well known by transporter workers.     

Structure of the stigma and style of <Emphasis Type="Italic">Callaeum psilophyllum</Emphasis> (Malpighiaceae) and its relation with potential pollinators

The family Malpighiaceae, particularly in the Neotropic, shows a similar floral morphology. Although floral attraction and rewards to pollinators are alike, stigmas and styles show more diversity. The stigmas were described covered with a thin and impermeable cuticle that needs to be ruptured by the mechanical action of the pollinators. However, this characteristic was only mentioned for a few species and the anatomy and ultrastructure of the stigmas were not explored. In this work, we analyze the morphology, anatomy, and ultrastructure of the stigma and style of Callaeum psilophyllum. Moreover, we identify the potential pollinators in order to evaluate how the disposition of the stigmas is related with their size and its role in the exposure of the receptive stigmatic surface. Our observations indicate that Centris flavifrons, C. fuscata, C. tarsata, and C. trigonoides are probably efficient pollinators of C. psilophyllum. The three stigmas are covered by a cuticle that remained intact in bagged flowers. The flowers exposed to visitors show the cuticle broken, more secretion in the intercellular spaces between sub-stigmatic cells and abundant electron-dense components inside vacuoles in stigmatic papillae. This indicates that the stigmas prepares in similar ways to receive pollen grains, but the pollinator action is required to break the cuticle, and once pollen tubes start growing, stigmatic and sub-stigmatic cells release more secretion by a granulocrine process.     

Trap-nests used by Centris (Heterocentris) terminata Smith (Hymenoptera: Apidae, Centridini) at secondary Atlantic Forest fragments, in Salvador, Bahia State

Ninety-five nests of Centris (Heterocentris) terminata Smith were collected in trap-nests, during November/2001 and January/2003, at two fragments (PZGV e CFO-UFBA) of secondary Atlantic Forest, in Salvador, Bahia State (13 masculine01 W e 38 masculine30 S). The highest nest frequencies occurred from December to February (summer), with no nests foundations from August to October (winter - early spring). Two-hundred eight adults emerged from 347 brood cells, being 164 males and 116 females (1: 0.42). During the study period sex ratio was male biased (c2 = 9.342; gl = 10; P < 0.05). C. terminata nested in holes with diameters 6, 8, 10 mm, but 84,2% were constructed in 8 and 10 mm. nests had one to seven cells arranged in a linear series with the cells partitions built with a mixture of sand and resin or oil. Male is significantly smaller than female, which emerges from the first cells constructed. Immature mortality occurred in 14.1% of brood cells (n = 49), of which 13.0% were due fail in development and 1.2% due to parasitism of Coelioxys sp. (Hymenoptera: Megachilidae) e Tetraonyx sp. (Coleoptera: Meloidae). In the study site, weather, mainly pluviosity, rather than natural enemies influenced seasonal population abundance. The long period of nesting activity, local abundance and usage of trap nests, suggest the potential of C. terminata for management aiming at pollination of native and cultivated plants.     

沙地毛足蜂筑巢生物学研究

【目的】调查毛乌素沙地的一种群居独栖性野生毛足蜂Dasypoda hirtipes Panzer的巢穴结构及其日活动规律。【方法】采用目测和拍照等方法对沙地毛足蜂的整个筑巢过程进行了连续观测;采用挖掘、测量方法对毛足蜂巢内结构进行了观测。【结果】2008和2009年共挖掘巢穴22个,巢口直径为6.32～10.35 mm,巢穴具有多分枝的支道,一般有4～16个分支道,主道的深度为84～112 cm,巢室分布在主道周围的支道里面,每个支道里面仅有1个巢室,巢室深度为22～54 cm。巢室内壁无蜡层,较光滑,巢室内的花粉球底部有3个均匀大小的用来支撑花粉球的突起。对雌性成蜂日活动行为的观察结果显示,雌性个体一天内采集粉蜜的次数在6～8次,最后一次一般不携带花粉归巢。【结论】在内蒙古毛乌素沙地,该蜂一年1代,日活动时间与菊科植物抱茎苦荬菜Ixeris sonchifolia花序中的单花期相对应,主要的蜜源植物为菊科植物和蒺藜属植物。     

Reproductive seasonality and nest-site differentiation in three closely related armoured catfishes (Siluriformes: Callichthyidae)

Synopsis Three sympatric, closely related armoured catfishes showed a similar, bimodal breeding season in coastal plain swamps in Suriname (South America). The bimodal pattern of reproduction inCallichthys callichthys,Hoplosternum littorale andHoplosternum thoracatum was correlated to the annual distribution of rainfall. Floating bubble nests were constructed throughout the period of swamp inundation (rainy season). Close inspection of the timing of reproduction ofH. littorale in northern South America revealed the relationship between reproduction and rainfall, but also unexpected differences in the length of the breeding season. Strong interspecific competition among the three species was probably avoided through differentiation of nest sites with respect to water depth, distance to the nearest tree, distance to the edge of the swamp, and cover above the nest. Nests ofH. littorale were built in herbaceous swamps, whileC. callichthys andH. thoracatum build their nests in swamp-forest. Nests ofC. callichthys were observed in extremely shallow water or in holes. Few nests of the three species were observed in canals. Over large parts of their geographical rangeC. callichthys andH. thoracatum are found in small rainforest streams. Several aspects of the reproductive ecology and behaviour of both species are probably related to the unpredictability of the stream habitat.     

铬黄圆痕叶蝉属的订正及圆痕叶蝉族巴西二新属二新种描记（半翅目：叶蝉科）

基于比较形态学对曾归入圆痕叶蝉亚科铬黄圆痕叶蝉属Chromagallia的8个有效种（C. saucia (St?l), C. flavofasciata (St?l), C. longistilata (Coelho & Dutra), C. carvalhoi Gon?alves et al., C. lamasi Gon?alves et al., C. lanceolata Gon?alves et al., C. paraguayensis Gon?alves et al.和C. zanolae Gon?alves et al.）进行了订正,明确了该属的范围仅限于具有黄斑的3个种（C. flavofasciata (St?l), C. longistilata (Coelho & Dutra) 和C. rodriguesoi sp. nov.）,对该属进行了重新描述,并修订了鉴别特征。此外,对模式种C. flavofasciata 进行了重新描记,首次提供了C. longistilata的雌性生殖器图,并作了描记。把曾归入铬黄圆痕叶蝉属Chromagallia具有红斑的6个种移出并新建了2个新属：Rubragallia 和Neorubragallia,其中Rubragallia 包括R. saucia (St?l) n. comb.和R. paraguayensis (Gon?alves et al.) n. comb., Neorubragallia包括N. lamasi (Gon?alves et al.) n. comb., N. lanceolata (Gon?alves et al.) n. comb., N. zanolae (Gon?alves et al.) n. comb., N. carvalhoi (Gon?alves et al.) n. comb. 和N. mervini sp. nov.。文中提供了3个属的分种检索表,并对不同种的分类地位及3个属的划分进行了讨论。     

Predatory behaviors of Neoseiulus californicus and Galendromus helveolus (Acari: Phytoseiidae) attacking Oligonychus perseae (Acari: Tetranychidae)

Predatory behaviors of Neoseiulus californicus (McGregor) and Galendromus helveolus (Chant) attacking Oligonychus perseae Tuttle, Baker and Abbatiello on avocado leaves were videotaped and analyzed. Behaviors were recorded for “fresh” predators that were used ≤ 48 hr post receipt from a commercial insectary and “cold stored” predators that were maintained at 12°C for ≈ 14 days. Fresh and cold stored G. helveolus were observed to attack O. perseae only after invading webbed nests. Conversely, fresh and cold stored N. californicus employed three different modes of predatory attack: (1) intercepting and attacking migrant O. perseae outside of web nests; (2) attacking prey through nest webbing; or (3) invading and attacking O. perseae inside nests. Predatory efficacy of both N. californicus and G. helveolus was reduced following cold storage, as both species engaged in certain predatory behaviors less frequently in comparison to predators that were not stored at low temperatures. Our observed results for N. californicus and G. helveolus attacking O. perseae are interpreted in relation to the chaetotaxy hypothesis, which proposes that phytoseiid invasion efficiency and propensity of webbed nests is facilitated by dorsal setal lengths. This revised version was published online in July 2006 with corrections to the Cover Date.     

Ground nesting in the paper wasp <Emphasis Type="Italic">Polistes aurifer</Emphasis> (Hymenoptera,Vespidae)

Summary Polistes paper wasp species vary in their nest site selection, with some nesting in relatively exposed areas and others in protected cavities. Locating the nest sites of cavity dwelling species in natural habitat can prove difficult, and most behavioral studies on these species are therefore conducted using human-built structures. Since Hungerford and Williams (1912) and Rau (1929) noted the location of several P. fuscatus (Fabricius) nests in rodent burrows, there have been no published accounts of ground nesting Polistes species. I report the occurrence of a large, dense cluster of P. aurifer (Saussure) nests located within cracks in the dried soil of the Santa Monica Mountains of southern California, USA.Received 8 April 2003; revised 10 October 2003; accepted 31 October 2003.     

Effect of Average Worker Size on Tunneling Behavior of Formosan Subterranean Termite Colonies

The effect of a colony's average worker size on tunneling behavior of Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae) in laboratory foraging arenas was investigated. Large groups of foragers from four colonies were added to arenas and allowed to tunnel for a period of 22 days. Various aspects of the resulting tunnel galleries were analyzed using ANOVA and regression analysis. After the exclusion of one colony due to high mortality, the only parameters shown to differ significantly were tunnel width and tunnel segmentation. Larger workers tended to construct less segmented galleries with wider tunnels. Tunnel length was positively correlated to size on the first 2 days, but the relationship reversed by day 4. Tunneling on day 1 was positively correlated to the discovery of food items. Our results indicate that a foraging group's average worker size can affect tunnel pattern and that groups composed of larger workers are better tunnelers, but groups of smaller sized workers are able to make up the difference over time. Possible explanations for size-related variation in tunneling behavior are discussed.     

Experimental analyses of competition between two species of bumble bees (Hymenoptera: apidae)

Summary Dynamical aspects of flower usage and forager body size in sympatric and experimentally-induced allopatric populations of Bombus flaviforns and Bombus rufocinctus were studied in 10 discrete subalpine meadows and over the last half of one summer. Results indicate that there is a high degree of asymmetry in the competitive effects and that B. flavifrons is the clear competitive and numerical dominant. When occurring alone, B. rufocinctus used the same spectrum of flowers in similar frequencies to that of B. flavifrons whose flower use was invariant over all meadows and treatments. When sympatric with B. flavifrons, B. rufocinctus was relegated to secondary, less preferred flowers. Shifts in flower use by B. rufocinctus were accompanied by changes in forager body-size: body weights were greater in allopatric populations of B. rufocinctus and smaller in those sympatric with B. flavifrons. Competitive dominance may be related to differences in species phenologies. Bombus flavifrons initiated colonies in the spring three weeks before B. rufocinctus and maintained higher densities over the summer; by virtue of greater numbers of foragers, it may control exploitation of the most profitable flowers.