The saws of sawflies: exploring the morphology of the ovipositor in Tenthredinoidea (Insecta: Hymenoptera), with emphasis on Nematinae

Host use by 2 sibling species of bogus yucca moths in relation to plant hardness and saponin content

Plant defenses allow plants to deter or kill their insect herbivores and are considered to be a major driver of host use for herbivorous insects in both ecological and evolutionary time. Many closely related species of insect herbivores differ in their ability to respond to plant defenses and in some cases are specialized to specific plant species. Here we tested whether both mechanical and chemical plant defenses are a major factor in determining the host range of 2 sibling species of Prodoxid bogus yucca moths, Prodoxus decipiens (Riley) and Prodoxus quinquepunctellus (Chambers) that feed within the inflorescence stalk of Yucca species. These 2 moth species have separate suites of host plant species, yet narrowly overlap geographically and share 1 Yucca species, Y. glauca. We surveyed the lignin and cellulose content, the force required to the puncture the stalk tissue, and saponin concentration across 5 Yucca species used as hosts. Lignin, cellulose concentrations, and stalk hardness differed among Yucca species but did not correlate with host use patterns by the moths. Saponin concentrations in the stalk tissue were relatively low for yuccas (<1%) and did not differ among species. The results suggest that these moth species should be able to use each other's hosts for egg deposition. Additional factors such as larval development or competition among larvae for feeding space may serve to keep moth species from expanding onto plants used by its sibling species.

Fine Morphology of Antennal and Ovipositor Sensory Structures of the Gall Chestnut Wasp, Dryocosmus kuriphilus

Dryocosmus kuriphilus is a gall-inducing insect, which can cause significant damage on plants of the genus Castanea Mill., 1754. Antennae and ovipositor are the main sensory organs involved in the location of suitable oviposition sites. Antennal sensilla are involved in the host plant location, while ovipositor sensilla assess the suitability of the ovipositional bud. On both organs, diverse sensillar organs are present. Here, the distribution and ultrastructural organization of the sensilla were investigated by scanning and transmission electron microscopy. The antennae of D. kuriphilus are filiform and composed of 14 antennomeres, with the distal flagellomere bearing the highest number of sensilla. On the antennae, 6 sensilla types were found; sensilla chaetica, campaniformia, coeloconica-I, coeloconica-II, trichoidea and placoidea. The sensilla placoidea and trichoidea were the most abundant types. On the external walls of the ovipositor, gustatory and mechanoreceptive sensilla were observed. Internally, the egg channel hosted two additional sensory structures. The putative functional role of each sensilla in the context of insect's ecology is discussed as well as the ovipositional mechanism used by this insect.

From Arge to Zenarge: adult morphology and phylogenetics of argid sawflies (Hymenoptera: Argidae)

The Argidae is the second most diverse family of the ‘Symphyta’ with more than 900 described species. Here we present the first comprehensive phylogenetic study for the family. We compare the adult skeleton anatomy of representatives of 57 described argid genera from different biogeographic regions. We score 223 characters for 117 terminal taxa, and apply maximum parsimony inference to reconstruct the phylogeny, using equal weights and implied weights analyses. The Argidae sensu stricto, i.e. all Argidae except Zenarge, are consistently retrieved as monophyletic. The position of Zenarge changes according to the implied weighting parameters: ((Zenarge+Pergidae)+Argidae) at low (1–3) k-values, (Zenarge+(Pergidae+Argidae)) at high (4–30) k-values. We describe in detail the skeletal anatomy of Zenarge turneri and propose to raise it to family status: Zenargidae stat. revis. We consider the ridge on the teloparameres (=harpes) of the male genitalia to be the main autapomorphy of adults of the Argidae sensu stricto. We recover two main clades within the family and suggest recognizing these as the subfamilies Arginae and Sterictiphorinae. We trace the evolution of characters on the preferred implied weights tree. The genera Arge, Didymia, Pampsilota, Ptenos and Sphacophilus were paraphyletic.

Functional morphology of the sting in two digger wasps (Hymenoptera: Crabronidae) with different types of prey transport

Digger wasps of the family Crabronidae (Insecta: Hymenoptera) are generally known to use their sting to paralyze or kill a prey. However, only a few species of digger wasps transport their prey to the nest impaled on the sting. How sting morphology correlates with this peculiar type of prey carriage is still unclear. We examined the sting morphology of two phylogenetically closely-related species of digger wasps of similar size, which hunt for similar preys but use different types of prey transportation. Data from light microscopy (LM), scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) were analyzed to find possible correlations between shape, material composition, and function of the stings. The similarity of the material composition in the stings of the two species suggests that the material of stings does not play a dominant role in their functional differences. On the contrary, differences in the curvature and surface sculpture of sting elements likely result in different stress distributions under mechanical loading.

First report of Tequus schrottkyi (Konow) (Hymenoptera: Pergidae) in Uruguay, and information about its host plant and biology

Background

The sawfly family Pergidae is best represented in South America, and it is the third largest family in the suborder Symphyta. Tequus is a Neotropical genus that has been reported in association with host plants of the genus Solanum (Solanaceae), with little information about the life history of its members. Tequusschrottkyi (Konow, 1906) was described from Paraguay, without any information about its biology and host plant.

New information

We report the first record of T.schrottkyi from Uruguay, with information on its host plant and details of its biology. The identification was based on morphology, DNA barcode is provided to allow identification using molecular characters. This sawfly species is associated with Solanumcommersonii, a native plant common in Uruguay. Tequusschrottkyi presents several generations between March and July. The larvae feed on leaves and spin a silk cocoon in the soil in which they pupate. The adults exhibit sexual dimorphism, the female being larger than the male and with a different color pattern. The eggs are laid individually in the leaf margins into the leaf tissue. The larvae are unpalatable to a generalist predator, possibly due to defensive compounds sequestered from their host plant, known to contain toxic compounds.

Morphological phylogenetics of the Tenthredinidae (Insecta : Hymenoptera)

The Tenthredinoidea is the most diverse superfamily of non-apocritan Hymenoptera. It is also one of the largest herbivorous groups within the order, some species having substantial economic impact. Until very recently, no comprehensive phylogenetic analyses of the superfamily had been undertaken. This paper presents the largest morphological dataset assembled so far for elucidating the phylogeny of the Tenthredinoidea. In total, 129 taxa were scored for 146 characters from the adult head, thorax, wings and ovipositor apparatus. The emphasis of the taxon sample is on Tenthredinidae (104 terminals), which is by far the largest family in the Tenthredinoidea. The results of the cladistic analyses confirm the monophyly of the Tenthredinoidea, the first split being between the Blasticotomidae and the remaining families (Tenthredinoidea s. str., also monophyletic), and the monophyly of all families except Tenthredinidae. The analyses fail to consistently retrieve any of the six currently recognised subfamilies within Tenthredinidae, although core clades of Heterarthrinae, Nematinae, Selandriinae and Tenthredininae are often supported. Diprionidae are placed inside the Nematinae under some weighting conditions. The failure to corroborate the tenthredinid subfamilies might be ascribed to an insufficient character/terminal ratio, but also to problems with the existing classification. Inclusion of characters from the male genitalia and the larval stages as well as molecular data currently being assembled will hopefully lead to a more robust classification of the Tenthredinidae in the future.