Sex ratio variation as a function of host size in Pseudacteon flies (Diptera: Phoridae), parasitoids of Solenopsis fire ants (Hymenoptera: Formicidae)

Some Pseudacteon (Diptera: Phoridae) flies are parasitoids of Solenopsis (Hymenoptera: Formicidae) ant workers in North and South America. Laboratory studies of sex allocation revealed a pattern of sex ratio variation as a function of host size, with more females arising from larger hosts. Environmental sex determination is a possible mechanism for the observed pattern, and examination of Pseudacteon life history reveals several traits assumed to be important in models predicting conditions under which environmental sex determination is favoured. Sex allocation patterns of Pseudacteon are compared with theoretical predictions and empirical data from better-studied hymenoptcran parasitoids that have haplodiploid sex determination. The pattern of sex ratio variation observed has important implications for biocontrol efforts of imported Solenopsis fire ants by the introduction of Pseudacteon parasitoids.     

New Technology for Estimating Seed Production of Moist-Soil Plants

ABSTRACT Waterfowl biologists estimate seed production in moist-soil wetlands to calculate duck-energy days (DEDs) and evaluate management techniques. Previously developed models that predict plant seed yield using morphological measurements are tedious and time consuming. We developed simple linear regression models that indirectly and directly related seed-head area to seed production for 7 common moist-soil plants using portable and desktop scanners and a dot grid, and compared time spent processing samples and predictive ability among models. To construct models, we randomly collected approximately 60 plants/species at the Tennessee National Wildlife Refuge, USA, during September 2005 and 2006, threshed and dried seed from seed heads, and related dry mass to seed-head area. All models explained substantial variation in seed mass (R²< 0.87) and had high predictive ability (R²_predicted < 0.84). Processing time of seed heads averaged 22 and 3 times longer for the dot grid and portable scanner, respectively, than for the desktop scanner. We recommend use of desktop scanners for accurate and rapid estimation of moist-soil plant seed production. Seed predictions per plant from our models can be used to estimate total seed production and DEDs in moist-soil wetlands.     

The Ultrastructure of Encephalitozoon cuniculi (Microsporida,Nosematidae) and its Taxonomic Significance*

SYNOPSIS. This study augments our knowledge of several ultrastructural features of Encephalitozoon cuniculi and provides evidence that this species is disporous. We support Cali's view that Encephalitozoon is distinct from Nosema and should be treated as a valid genus. We compare these with 2 other disporous genera, Glugea and Perezia, and conclude that Glugea is also distinct but Perezia is a junior synonym of Nosema.     

Light and Electron Microscope Study of a New Species of Glugea (Microsporida,Nosematidae) in the 4-Spined Stickleback Apeltes quadracus*

SYNOPSIS. Cell hypertrophy tumors (xenomas) associated with Glugea weissenbergi n. sp. frequently occur under the peritoneum (parietal or visceral) of Apeltes quadracus (Mitchell) near Solomons Island, Maryland. The microsporidan is similar to the type species, G. anomala (Moniez, 1887) Gurley, 1893, but has larger spores. Its fine structure corresponds with the basic pattern revealed by other authors in various species of Nosematidae. A concept of spore morphogenesis, in which the polar filament primordium is 1/2 of the nuclear isthmus present during division of the sporont, is elaborated and its implications discussed. The membrane systems of the Glugea and host cell components appear to be continuous with one another, this being an indication that the membranes are all furnished by the host cell. Lacking mitochondria and (apparently) a Golgi apparatus, Glugea is, when considered apart from the membrane system which is common to it and the host cell, a very simple organism, consisting of very little besides the genome. The simplicity of the Glugea, its very high degree of structural and physiological integration with the host cell, and the transformative development of the host cell all suggest an analogy with certain viruses.     

Ultrastructure of the Water-absorbing Trichomes of Pineapple (Ananas comosus, Bromeliaceae)

An ultrastructural study of dry and wet trichomes from the upperleaf surface of pineapple revealed that shield cells were normallydead and stalk cells were often living. In stalk cells of drytrichomes, polysaccharide material was present within vacuolesand a layered material was present between the plasma membraneand cell wall. In stalk cells of trichomes wet for 12 h vacuoleswere enlarged and appeared to contain little material. Layeredmaterial between the plasma membrane and cell wall was alsoabsent. In both wet and dry trichomes, numerous mitochondriawere present and plasmodesmata were observed connecting stalk,foot, and adjacent epidermal and mesophyll cells. It is suggestedthat the large numbers of mitochondria, which indicate highmetabolism, and the numerous plasmodesmata connecting the cells,provide indirect evidence for the function of the trichomesin uptake of dissolved nutrients. Ananas comosus (L.) Merr., pineapple, trichomes, ultrastructure, Bromeliaceae     

Niche modelling of the Chilean recluse spider Loxosceles laeta and araneophagic spitting spider Scytodes globula and risk for loxoscelism in Chile

In Chile, all necrotic arachnidism is attributed to the Chilean recluse spider Loxosceles laeta (Nicolet) (Araneae: Sicariidae). It is predated by the spitting spider Scytodes globula (Nicolet) (Araneae: Scytodidae). The biology of each of these species is not well known and it is important to clarify their distributions. The aims of this study are to elucidate the variables involved in the niches of both species based on environmental and human footprint variables, and to construct geographic maps that will be useful in estimating potential distributions and in defining a map of estimated risk for loxoscelism in Chile. Loxosceles laeta was found to be associated with high temperatures and low rates of precipitation, whereas although S. globula was also associated with high temperatures, its distribution was associated with a higher level of precipitation. The main variable associated with the distribution of L. laeta was the human footprint (48.6%), which suggests that this is a highly invasive species. Similarly to other species, the distribution of L. laeta reaches its southern limit at the Los Lagos region in Chile, which coincides with high levels of precipitation and low temperatures. The potential distribution of L. laeta in Chile corresponds to the distribution of cases of loxoscelism.     

The radiation of Satyrini butterflies (Nymphalidae: Satyrinae): a challenge for phylogenetic methods

We have inferred the most comprehensive phylogenetic hypothesis to date of butterflies in the tribe Satyrini. In order to obtain a hypothesis of relationships, we used maximum parsimony and model‐based methods with 4435 bp of DNA sequences from mitochondrial and nuclear genes for 179 taxa (130 genera and eight out‐groups). We estimated dates of origin and diversification for major clades, and performed a biogeographic analysis using a dispersal–vicariance framework, in order to infer a scenario of the biogeographical history of the group. We found long‐branch taxa that affected the accuracy of all three methods. Moreover, different methods produced incongruent phylogenies. We found that Satyrini appeared around 42 Mya in either the Neotropical or the Eastern Palaearctic, Oriental, and/or Indo‐Australian regions, and underwent a quick radiation between 32 and 24 Mya, during which time most of its component subtribes originated. Several factors might have been important for the diversification of Satyrini: the ability to feed on grasses; early habitat shift into open, non‐forest habitats; and geographic bridges, which permitted dispersal over marine barriers, enabling the geographic expansions of ancestors to new environments that provided opportunities for geographic differentiation, and diversification.

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False fairy wasps in Early Cretaceous amber from Spain (Hymenoptera: Mymarommatoidea)

Abstract: The fauna of false fairy wasps (Proctotrupomorpha: Bipetiolarida: Mymarommatoidea) occurring in Early Cretaceous (Albian) amber from north and north‐eastern Spain (Moraza, San Just, and El Soplao outcrops) is described. In total, 12 specimens have been recovered and four species recognized, all new: Alavaromma orchamum gen. nov. and sp. nov. (Alavarommatidae fam. nov.), Archaeromma hispanicum sp. nov. (Mymarommatidae), Galloromma alavaensis sp. nov., and G. turolensis sp. nov. (Gallorommatidae). The study indicates the necessity of revision and maybe fusion of both superfamilies, Mymarommatoidea and Serphitoidea, as the boundaries between them are less and less defined. However, major classificatory rearrangements must await the completion of the cladistic studies presently underway.