Short-range attraction and oviposition stimulant of a biocontrol agent, Galerucella placida Baly (Coleoptera: Chrysomelidae) toward weed leaf surface waxes

Two Polygonaceae weeds, Rumex dentatus L. and Polygonum glabrum Willd. are abundant in wheat- and rice-fields, respectively, in India. Galerucella placida Baly (Coleoptera: Chrysomelidae) is a biocontrol agent of these two weeds. The importance of long-chain alkanes and free fatty acids present in leaf surface waxes of these weeds was assessed as short-range attractant and ovipositional stimulant in G. placida females. Extraction, TLC, GC-MS and GC-FID analyses demonstrated 19 n-alkanes from n-C14 to n-C35 and 14 free fatty acids from C12:0 to C22:0 in leaf surface waxes. Hentriacontane was predominant among alkanes in both weeds, while oleic acid and docosanoic acid were predominant among free fatty acids in R. dentatus and P. glabrum, respectively. Females of G. placida were attracted toward one leaf equivalent surface wax of both weeds against the control solvent (petroleum ether) in a short Y-tube olfactometer bioassay. But, the insect could not differentiate between one leaf equivalent surface wax of R. dentatus and P. glabrum, indicating that both weed leaves were equally attractive in females. A synthetic blend of either 2.44, 35.57 and 23.58 μg ml−1 of octadecane, heptacosane and nonacosane, respectively, resembling the amounts present in one leaf equivalent surface wax of R. dentatus or 4.08, 19.54 and 23.58 μg ml−1 of octadecane, palmitoleic acid and docosanoic acid, respectively, resembling the amounts present in one leaf equivalent surface wax of P. glabrum acted as short-range attractant and ovipositional stimulant in G. placida. These results could be a basis for host plant specificity of the biocontrol agent.

Host plant specificity of corticolous lichens in urban and suburban New Amsterdam, Berbice, Guyana

In this study, host plant - lichen specificity was investigated. Data was collected from 1000m2 sampling plots at each of four locations with an established 50m x 20m plot at each site. Forty-one trees from across five species were examined using (10cm by 50cm) ladder quadrats on tree trunks (N, S, E, W) at 150cm height. A total of 14978 individual lichens were identified that yielded 10 families, 13 genera and 18 species. Swietenia mahagoni showed the highest average corticolous lichen species composition, followed by Terminalia catappa and Melicoccus bijugales respectively. Cocos nucifera had a higher average species recorded than Mangifera indica. Crustose lichens were the most prominent corticolous lichens observed (61%) with the most individuals in Graphidaceae and Arthoniaceae. Foliose lichens (28%) showed the most abundance in Parmeliaceae, Caliciaceae and Collemataceae. Of the taxa recorded, 22.2% were restricted to specific trees. C. parasitica, H. laevigata, U. cornuta were restricted to S. mahagoni. D. applanata was restricted to C. nucifera. 22.2% of recorded species were found on all of the tree hosts that were examined. Bacidia laurocerasi, Flavoparmelia caperata, Flavoparmelia soredians and Graphina anguina. S. mahagoni hosted 88.9% of all recorded species. Swietenia mahagoni showed the highest average of recorded corticolous lichen species of all host trees with 7.58. Mangifera indica showed the lowest average with 4. The maximum number of species (10) was recorded on one S. mahagoni tree

Congeneric mutualist ant symbionts (Tetraponera, Pseudomyrmecinae) differ in level of protection of their myrmecophyte hosts (Barteria, Passifloraceae)

Barteria fistulosa and B. dewevrei, central African rain-forest trees, provide nesting cavities for Tetraponera aethiops and T. latifrons ants, respectively, which protect them against herbivores. To compare protection efficiency between these two symbioses, for 20 plants of each species in two sites in Gabon we measured the time elapsed before ants reached a focal leaf, for host leaves that were undisturbed, damaged (cut with scissors) or subjected to slight vibration (mimicking such damage), and for damaged leaves of the non-host Barteria species. Tetraponera aethiops displayed stronger protective behaviour than did T. latifrons. Time to reach a damaged host leaf (4.5 ± 2.6 min, mean ± SD) did not differ significantly from time to reach a leaf subjected to slight vibration (5.2 ± 3.0 min) for T. aethiops, but response to a leaf subjected to slight vibration (9.5 ± 1.9 min) was significantly slower than that to a damaged leaf (7.8 ± 1.9 min) for T. latifrons. The faster response of T. aethiops to slight vibration may have masked a response of this species to chemical signalling. Both ants reached damaged host leaves faster than damaged leaves of the non-host Barteria sp., indicating host plant specificity in ant responses.

Host plant specificity and feeding preferences of Morpho epistrophus argentinus (Lepidoptera: Nymphalidae) larvae in coastal woodlands of Argentina

The selection of suitable host plants for larval development is critical for most herbivorous insects. In this study, we examined host plant preferences of larvae of the Epistrophus white morpho butterfly, Morpho epistrophus argentinus (H. Fruhstorfer), a specialized butterfly that oviposits on a few plant species. In many species, the selection of host plant species for larvae development is under the control of ovipositing females and the role of larvae in host selection is minimal. Through field observations, we characterized larval host plant use in coastal woodland patches of its southernmost distribution range at eastern Buenos Aires, Argentina. All sampled M.e. argentinus larvaegroups (n = 40) were found on Scutia buxifolia trees, although the number of larval groups did not correlate with cover of this plant at patch scale. To further examine host plant preferences we performed translocation experiments and feeding choice assays. M.e. argentinus larvae translocated to unsuitable host plants had a shorter residence time than those translocated to suitable (i.e. control) hosts. Choice assays also indicated strong feeding preferences of wild larvae for S. buxifolia leaves. Our results highlight the high degree of host specificity of this butterfly, and reveal that host preference of growing larvae matches that of ovipositing females.

No Indication of High Host-Plant Specificity in Afrotropical Geometrid Moths

Specificity is one of the fundamental concepts in ecology. Host specificity of phytophagous insects has been of particular interest because of its crucial role in diversification and life-history evolution. However, the majority of tropical insects remain insufficiently explored with respect to their host-plant relations. A lack of respective data is also hindering the debate over whether higher levels of host-plant specificity prevail in tropical insects compared to temperate ones. We investigated host-plant specificity of forest geometrid moths (Lepidoptera: Geometridae) in equatorial Africa using host-plant acceptability trials with neonate larvae, with the addition of field observations. We compare our experimental data to the (well-known) host-specificity patterns of closely related temperate (hemiboreal) species. Similarly to the temperate region, there were broadly polyphagous tropical species in several clades of Geometridae utilizing hosts belonging to different plant families. Phylogenetic comparative analysis returned no significant differences in host specificity between the two regions. Our study contributes to the evidence that host-plant specificity of herbivores is not necessarily substantially higher in tropical than temperate regions.

Not Led by the Nose: Volatiles from Undamaged Eucalyptus Hosts Do Not Influence Psyllid Orientation

Psyllids (Hemiptera: Psylloidea) are small sucking insects with high host plant specificity. Despite the primitive olfactory system of psyllids, some species have been suggested to rely on host plant volatiles (HPVs) for seasonal migration between summer deciduous hosts and winter coniferous hosts. Similarly, enhanced attraction of psyllid vectors has been observed as a result of the manipulation of host odors by plant pathogens. As yet, there are no studies of olfaction in psyllids that utilize evergreen eucalypt hosts. We investigated the behavioral responses of adults of four Eucalyptus-feeding psyllids—Ctenarytaina eucalypti, C. bipartita, Anoeconeossa bundoorensis and Glycaspis brimblecombei—to their respective HPVs in Y-tube olfactometer bioassays. We also used existing physiological data for C. eucalypti to investigate potential olfactory tuning that may modulate the preference for morphologically juvenile leaves over morphologically adult leaves. Although adult C. eucalypti were consistently repelled by HPVs from damaged host leaves, none of the species exhibited positive chemotaxis to HPVs from undamaged leaves. Surprisingly, G. brimblecombei was repelled by HPVs from undamaged host leaves. Our findings provide little support for a significant role of olfaction in host location by Eucalyptus-feeding psyllids. We propose a number of ecological hypotheses to explain these unexpected findings.

North European gall-inducing Euura sawflies (Hymenoptera, Tenthredinidae, Nematinae)

The sawfly genus Euura of the tenthredinid subfamily Nematinae, in which species level taxonomy has long been regarded as controversial, is particularly species rich in northern parts of the Holarctic. Among a majority of species with more or less free-living larvae, a sizeable minority belongs to a monophyletic lineage whose larvae complete their whole development in galls. We present illustrated keys to the adults and galls of 66 gall-inducing Euura species that occur, or might occur, in northern Europe. The distribution of these species is briefly reviewed, with an emphasis on the fauna of Sweden, where 55 species are now definitely recorded, two of them for the first time (E. bigallae, E. myrtilloidica). The species-level taxonomy of gall-inducing Euura remains partly problematic. Nominal species described on the basis of experimentally tested or assumed host plant specificity, but which cannot be recognised using morphological or genetic characters, are treated as conspecific with currently indistinguishable segregates ("host-plant races") associated with other Salix species. 20 new synonymies are proposed (valid names in parentheses): Eupontania acutifoliae baltica Vikberg & Zinovjev, 2006 and Pontania acutifoliae daphnoides Zinovjev, 1993 (Euura acutifoliae (Zinovjev, 1985)), Euura boreoalpina Kopelke, 2001 (Euura lanatae Malaise, 1921), Euura cinereae Kopelke, 1996 preoccupied and Euura lapponica Kopelke, 1996 preoccupied (Euura auritae Kopelke 2000), Euura gemmacinereae Kopelke, 2001 and E. nigritarsis Cameron, 1885 (Euura mucronata (Hartig, 1837)), Euura phylicifoliae Kopelke, 2001 (Euura myrsinifoliae Kopelke, 2001), Nematus westermanni Boheman, 1852 nomen oblitum (Euura scotaspis (Förster, 1854) nomen protectum), Nematus acerosus Hartig, 1840 (Euura saliciscinereae (Retzius, 1783)), Nematus alienatus Förster, 1854 and Phyllocolpa rolleri Liston, 2005 (Euura leucapsis (Tischbein, 1846)), Nematus angustus Hartig, 1837 (Euura atra (Jurine, 1807)), Nematus erythropygus Förster, 1854 (Euura leucosticta (Hartig, 1837)), Nematus impunctatus Herrich-Schäffer, 1840 (Euura amerinae (Linnaeus, 1758)), Pontania carinifrons Benson, 1940 and Phyllocolpa plicaglauca Kopelke, 2007 (Euura destricta (MacGillivray, 1923)), Pontania obscura Kopelke, 2005 (Euura bridgmanii (Cameron, 1883)), Pontania viminalis var. lugubris Enslin, 1918 and Eupontania collactanea rosmarinifoliae Vikberg & Zinovjev, 2006 (Euura collactanea (Förster, 1854)). Euura weiffenbachiella nom. nov. is proposed as a replacement name for Euura weiffenbachii Ermolenko, 1988; preoccupied in Euura by Pteronidea weiffenbachi Lindqvist, 1958 (Euura piliserra (Thomson, 1863)). Lectotypes are designated for the following 9 taxa: Euura insularis Kincaid, 1900, Euura lanatae Malaise, 1921, Euura lappo Malaise, 1921, Euura lappo var. hastatae Malaise, 1921, Nematus acerosus Hartig, 1840, Nematus leptocerus Förster, 1854, Nematus vallisnierii Hartig, 1837, Pontania megacephala Rohwer, 1908, and Pontania piliserra var. mascula Enslin, 1915. Because of secondary homonymy within Euura, the valid name of the Nearctic species E. arctica MacGillivray, 1919 is E. delicatula (MacGillivray, 1919). The Nearctic Euura megacephala is removed from synonymy with the Holarctic E. destricta and treated as a valid species. 34 species names are newly combined with Euura.

Scale insect host ranges are broader in the tropics

The specificity of the interactions between plants and their consumers varies considerably. The evolutionary and ecological factors underlying this variation are unclear. Several potential explanatory factors vary with latitude, for example plant species richness and the intensity of herbivory. Here, we use comparative phylogenetic methods to test the effect of latitude on host range in scale insects. We find that, on average, scale insects that occur in lower latitudes are more polyphagous. This result is at odds with the general pattern of greater host-plant specificity of insects in the tropics. We propose that this disparity reflects a high cost for host specificity in scale insects, stemming from unusual aspects of scale insect life history, for example, passive wind-driven dispersal. More broadly, the strong evidence for pervasive effects of geography on host range across insect groups stands in stark contrast to the weak evidence for constraints on host range due to genetic trade-offs.