Diet does not affect intercolonial fighting in Leptothoracine ants

Summary An experiment examined the effects of diet on brood rearing in colonies ofLeptothorax ambiguus andL. longispinosus and on fighting between colonies of the two species. Colonies fedDrosophila and honey reared more pupae than colonies fed the Bhatkar and Whitcomb (1970) diet. However, diet had no effect on intercolonial fighting.     

Habitat structure,dispersal strategies and queen number in two boreal Leptothorax ants

In two nearctic ants, Leptothorax canadensis and Leptothorax sp. A, young queens may either found their own nest solitarily after mating or seek adoption into an established colony. Whether a queen disperses or not is associated with genetically determined queen morphology in Leptothorax sp. A. Whereas a majority of winged queens attempt solitary colony founding after mating, most wingless, intermorphic queens return to their maternal nests and new colonies are founded by budding after hibernation. The latter strategy appears to be correlated with patchy, isolated habitats, whereas in extended boreal forests dispersal on the wing is probably more common. Alternative dispersal strategies strongly affect the average number of queens per colony and seasonal fluctuations of colony structure.     

NewLeptographium species from Indonesia and Eastern North America

Leptographium species have predominantly been described from North America, Canada and Europe. These fungi generally occur on conifers and many cause blue-stain of lumber. MostLeptographium species are also associated with insects and in particular, bark beetles (Coleoptera: Scolytidae). Recently, an unknown species ofLeptographium was isolated from pine infested with anIps sp. in Indonesia. In addition, two unknown species have been collected from red spruce (Picea rubra) and balsam fir (Abies balsamea) roots from high elevation sites in Eastern North America. The latter isolates are unusual in that they are associated with the feeding wounds made by the conifer swift mothKorscheltellus gracilus (Lepidoptera: Hepialidae), which is a habitat unique for species ofLeptographium. Comparison with knownLeptographium species has revealed that the isolates from Indonesia and those from Eastern North America represent three previously undescribed taxa. They are, therefore, described in this study asL. pineti sp. nov,L. abieticolens sp. nov. andL. peucophilum sp. nov.     

A new ethological test to study nestmate recognition in adult ants

Summary An ethological test was designed to investigate nestmate recognition in adult ants. Contrary to classic dyadic tests, it consisted of a choice situation where a tested-worker was faced with nestmate and non-nestmate workers. These were kept alive, tied down, and thus immobilised in the neutral arena to record the tested-worker's reactions independently of the behaviour of the others. Such tests, applied to the ponerine ant,Ectatomma tuberculatum, enabled us to record various measures of discrimination and to limit aggressive behaviours between alien ants, which often leads to serious injury in dyadic tests. They also demonstrated the influence of age on discrimination behaviour in this species.     

Doronomyrmex pocahontas: not a workerless parasite but still an enigmatic taxon (Hymenoptera,Formicidae)

Summary New data suggest that the North American antDoronomyrmex pocahontas Buschinger 1979, originally described as a workerless inquiline, is not a social parasite. Breeding experiments show a remarkable phenotypic plasticity, which is probably due to hybridization or to intraspecific polymorphism.     

A newly-discovered mode of colony founding among fire ants

Summary Queen ants start new colonies either unassisted by workers (independent founding), assisted by workers from their natal nest (dependent founding), or assisted by the workers of other species (dependent, socially parasitic). The monogyne form of the fire ant,Solenopsis invicta, founds independently in summer, but in the fall it also produces a few sexuals some of which overwinter, then fly and mate in early spring. These overwintered queens lack the nutritional reserves and behaviors for independent colony founding. Rather, they seek out unrelated, mature, orphaned colonies, enter them and exploit the worker force to found their own colony through intraspecific social parasitism. Success in entering orphaned colonies is higher when these lack overwintered female alates of their own. When such alates are present, orphaning causes some to dealate and become uninseminated replacement queens, usually preventing entry of unrelated, inseminated replacement queens. Such colonies produce large, all-male broods. Successful entry of a parasitic queen robs the host colony of this last chance at reproductive success. Only overwintered sexuals take part in this mode of founding.     

Host plants of someRhinanthoideae (Scrophulariaceae) of eastern North America

Twenty three species in 11 genera were examined in the field to determine hosts. OnlyStriga asiatica andSeymeria cassioides have a narrow host range being restricted to grasses and pines, respectively. These are the only species which cause pronounced and sometimes serious host damage. The other species attach to a great diversity of hosts.     

Morphological analysis of some cryptic species in the Acanthocyclops vernalis species complex from North America

Patterns of morphological variation and reproductive isolation were examined for several North American populations of copepods in the Acanthocyclops vernalis Fischer A., 1853 (Copepoda, Cyclopinae) species complex. The copepods were collected from six sites in Wisconsin, U.S.A. Morphological analysis of 120 adult females revealed that a character used previously to distinguish species in this group was unreliable because of phenotypic plasticity. Most of the morphological variance was due to environment (Laboratory vs. field) and to field site. Relatively little of the variation was due to measurement error or asymmetry. Multivariate ordination analysis produced poorly-defined clusters of individuals, suggesting that different biological species are difficult or impossible to distinguish using a set of easily-measurable morphological characters. In our study, morphological similarity was independent of geographic distance among sites, between 0.05 and 300 km. Isofemale lines within sites showed little or no reproductive isolation, but nearly complete isolation among sites. Reproductive isolation was also independent of morphology. These results suggest that the Acanthocyclops population at each site could be considered a distinct cryptic biological species. These copepods expressed morphological stasis – persistence of morphological uniformity despite reproductive isolation. Because of the effect of site and environment on morphology, we recommend using much larger collections (many sites), common garden experiments, and a multi-disciplinary approach (morphological, reproductive, chromosomal, and molecular) as the basis for future taxonomic research on putative copepod species.     

Species-specific effects of tending ants on the development of lycaenid butterfly larvae

The transfer of nutrients between organisms is a common feature of mutualism. The production of these food rewards is often assumed to be costly. Estimation of the costs of producing food rewards is important for understanding the overall effects of the interaction on fitness. When food rewards are harvested by several species differing in foraging behavior, costs to the producer may differ. The larvae of many species in the butterfly family Lycaenidae produce secretions consumed by tending ants. Here I report that three North American ant species, Formica perpilosa, Dorymyrmex sp. (smithi complex), and Forelius foetida, had no negative effect on the duration of development and adult size of the lycaenid Hemiargus isola. Moreover, tending by the ant Formica perpilosa significantly enhanced larval growth, resulting in butterflies that were 20% heavier than their untended counterparts. Tending by the ants Dorymyrmex sp. (smithi complex) and Forelius foetida had no effect on butterfly weight. Tended, nonfeeding larvae lost 69% more weight than untended, nonfeeding larvae. Taken together, the results suggest that, although ant tending imposes a physiological cost, H. isola larvae use behavioral or physiological mechanisms to compensate or overcompensate for nutrients lost to ants.     

Shade adaptation and shade tolerance in saplings of three Acer species from eastern North America

Summary Saplings of three, co-occurring maple species in a mature maple-beech forest differed in a suite of structural and physiological characters that separated the canopy species, Acer, saccharum, from the two subcanopy species, A. pensylvanicum and A. spicatum. Acer saccharum had both more dense wood and tougher and heavier but thinner leaves than the subcanopy species. Acer pensylvanicum had the largest, lightest leaves with high stomatal density and its canopy architecture was the most effective in terms of leaf display for light interception. Acer spicatum had weaker wood similar to that of A. pensylvanicum but also small, soft and relatively poorly displayed leaves. Both subcanopy species maintained marginally higher average rates of photosynthesis over the growing season in the understory environment. We consider juvenile A. saccharum only shade-tolerant, capable of persisting through long periods in the closed canopy until a gap occurs but not specifically adapted to the understory environment. Juvenile A. sacchrum appears to be constrained functionally by the requirements set by the canopy environment that adults will occupy. Characters such as high wood density are already expressed in the understory sapling; this investment in denser wood slows the growth of saplings, but is necessary for structural reasons in the adult. Juvenile A. saccaharum have morphological and photosynthetic characters better suited to gas exchange and extension growth under the increased photon flux densities in large forest gaps, characteristics that will also be advantageous in the sunlit canopy environment of adults.Both subcanopy maples appear to be more truly shade-adapted, although in somewhat different ways. Acer pensylvanicum has characteristics that enhance the potential for capture and utilization of sunflecks and is able to sustain higher growth rates than A. saccharum in the shaded subcanopy environment. Acer spicatum shares some shade-adapted features with A. pensylvanicum, and its habit of lateral spread through stem layering may confer an additional advantage in foraging for small light gaps.     

Intercontinental union of Argentine ants: behavioral relationships among introduced populations in Europe, North America, and Asia

Many invasive ants, including the Argentine ant Linepithema humile, form expansive supercolonies, within which intraspecific aggression is absent. The behavioral relationships among introduced Argentine ant populations at within-country or within-continent scales have been studied previously, but the behavioral relationships among intercontinental populations have not been examined. The present study investigated the levels of aggression among intercontinental Argentine ant populations by transporting live ants from Europe and California to Japan and conducting aggression tests against Japanese populations. Workers from the dominant supercolonies of Europe and California did not show aggressive behavior toward workers from the dominant supercolony of Japan, whereas they fought vigorously against workers from minor supercolonies. The three massive supercolonies, together with Argentine ants from Macaronesia, may be the largest non-aggressive unit formed by a social insect species in which intraspecific aggression exists. Absence or low levels of aggression at transcontinental scale, which may have derived from low genetic variation, may help introduced Argentine ants maintain expansive supercolonies. The lack of aggression implies possible frequent exchanges of individuals among the intercontinental populations mediated by human activities.     

Social organization in some primitive Australian ants. I.Nothomyrmecia macrops Clark

Summary Results of laboratory-based ethological studies on twoNothomyrmecia macrops colonies with individually marked workers are reported. Interactive behavioural acts constituted less than 1% of all those recorded, revealing a strong tendency by the ants not to engage in social contact. Very few workers performed queen-directed acts. They stayed near the queen, though seldom in direct contact. Division of labour was otherwise barely apparent, except that some individuals showed a propensity to guard the nest entrance. No exchange of food was observed between workers, workers and queen, or adults and larvae (apart from worker placement of prey items with larvae). A queen fed from aDrosophila carcass retrieved from the nest floor, without assistance from workers. Systematic scanned observations confirmed levels of inactivity higher than previously observed in ants (comprising almost 2/3 of recorded behavioural acts). The time budget for activities directed toward the immature stages was the same in both colonies, and fluctuated during the circadian period. Non-nestmate larvae added to worker groups were more frequently licked than nestmate larvae, but this might not involve the particular recognition of nestmateversus non-nestmate brood. These observations support the hypothesis thatNothomyrmecia is primitively eusocial, and of special significance in myrmecology.     

Gene Flow in the Exotic Colonizing LadybeetleHarmonia axyridisin North America

The introduced parasitoid,Aphytis melinusDeBach (Hymenoptera: Aphelinidae), is used for augmentative biological control of California red scale,Aonidiella aurantii(Maskell) (Homoptera: Diaspididae). Commercially reared wasps are reared on oleander scale,Aspidiotus neriiBouché (Homoptera: Diaspididae). Oleander scale covers lack the chemical,O-caffeoyltyrosine, a kairomone mediating host selection byA. melinus.Wasps reared on oleander scale but individually exposed, or primed, toO-caffeoyltyrosine more readily accepted California red scale for probing in laboratory bioassays and parasitized a greater proportion of available California red scale in the field than wasps reared similarly but not exposed toO-caffeoyltyrosine. Thus, it may be possible to improve host recognition of commercial, insectary-rearedA. melinusby exposing them toO-caffeoyltyrosine prior to release. The goal of this study was to develop an inexpensive but effective means of priming thousands of wasps simultaneously toO-caffeoyltyrosine. The most effective method, but potentially the most expensive, was simply to spray parasitized oleander scale on their host plant with diluteO-caffeoyltyrosine prior to wasp emergence. In additional experiments, using controlled doses of syntheticO-caffeoyltyrosine applied to scale covers, we showed that primed wasps require both a lower minimum dose ofO-caffeoyltyrosine for recognition and also respond to measuredO-caffeoyltyrosine doses more consistently than unprimed wasps. The ability to mass-prime thousands of wasps prior to release is a crucial step toward realizing the concept of behavioral improvement of host selection of parasitoids on a commercial scale.     

A comparison of the pollen wall ultrastructure of aureoid and non-aureoidSenecio species (Asteraceae) in North America

The structure of the pollen wall as revealed by transmission electron microscopy is presented for 29 speciesSenecio including 19 aureoid and ten non-aureoid species. The previous report of a helianthoid wall structure (exine with internal foramina) is confirmed for all the aureoid species examined while all of the non-aureoid taxa showed a senecioid pattern. The data provide support for the treatment of the aureoid complex as a distinct taxon.     

Bryocamptus pilosus n. sp. (Copepoda: Harpacticoida) from North America

A new species of Bryocamptus from North America, B. pilosus n. sp., is described and illustrated. Some remarks are made on the occurrence of a specific piliform seta on the ventral side of the caudal ramus in the vejdovskyi species group.     

Effects of the concurrent exclusion of ants and earwigs on aphid abundance in an organic citrus grove

Based on the well-known mutualism between ants (Hymenoptera: Formicidae) and aphids (Homoptera: Aphididae), we conducted a five-year experiment of ant-exclusion from the canopies of citrus trees as a possible method of biological control of aphids. However, our results showed that the exclusion of ants from the canopies increased, instead of reducing, aphid abundance. To explain this unexpected result, we reasoned that the exclusion of ants from the canopies might also have excluded crawling insects that prey on aphids, such as the European earwig (Forficula auricularia L., Dermaptera: Forficulidae). Such a possibility is supported by the negative relationship between aphid density and the abundance of earwigs, consistent with a top-down control of aphids by earwigs. In contrast, the abundance of other aphid predators (Coleoptera: Coccinellidae, and Heteroptera) had no such negative effect on aphid density but a positive one, suggesting a bottom-up control, and showed no differences between control and ant-excluded trees. Thus, the most likely explanation for the increase in aphid abundance in the ant-excluded trees is the absence of earwigs from the canopies of the experimental trees, providing further evidence of the major role that earwigs play as control agents of aphids in cultivated trees.     

A comparison of Phragmites australisin freshwater and brackish marsh environments in North America

This paper compares the available North Americanliterature and data concerning several ecologicalfactors affecting Phragmites australisin inlandfreshwater, tidal fresh, and tidal brackish marshsystems. We compare aboveground productivity, plantspecies diversity, and sediment biogeochemistry; andwe summarize Phragmiteseffects on faunalpopulations in these habitats. These data suggest thatPhragmitesaboveground biomass is higher thanthat of other plant species occurring in the samemarsh system. Available data do not indicate anysignificant difference in the aboveground Phragmitesbiomass between marsh types, nor doesthere appear to be an effect of salinity on height.However, Phragmitesstem density wassignificantly lower in inland non-tidal freshwatermarshes than in tidal marshes, whether fresh orbrackish. Studies of the effects of Phragmiteson plant species richness suggest that Phragmitesdominated sites have lower diversity.Furthermore, Phragmiteseradication infreshwater sites increased plant diversity in allcases. Phragmitesdominated communities appearto have different patterns of nitrogen cyclingcompared to adjacent plant communities. Abovegroundstanding stocks of nitrogen (N) were found to behigher in Phragmitessites compared to thosewithout Phragmites. Porewater ammonium(NH₄ ⁺) did not differ among plant covertypes in the freshwater tidal wetlands, but inbrackish marshes NH₄ ⁺was much higher inSpartinaspp. than in neighboring Phragmitesstands. Faunal uses of Phragmitesdominated sites in North America were found to vary bytaxa and in some cases equaled or exceeded use ofother robust emergent plant communities. In light ofthese findings, we make recommendations for futureresearch.     

The subgeneric nomenclature for the herbaceous-stemmed Smilax species (Smilacaceae) of North America

The several names and ranks given to the North American group ofSmilax with biovulate locules together with both herbaceous and nonprickly stems are listed chronologically and discussed nomenclaturally. It is concluded that this group of approximately nine species should be known at the generic rank asNemexia Raf. or at the rank of subgenus asSmilax subgenusLuiste Raf. or at section rank asSmilax sectionNemexia (Raf.) A. DC.