Functional and evolutionary aspects of mouthpart structure in parasitoid wasps

This paper considers specializations in mouthpart structure among parasitoid wasps. I commence with a brief survey of mouthpart specializations (mostly involving the mandibles only) that serve functions other than feeding: facilitating emergence of the parasitoid adult from its place of pupation; facilitating grasping of the partner in mating (phoretic copulation); facilitating excavation and/or protecting vulnerable mouthpart components during host searching; facilitating handling of the host; and facilitating nest excavation and construction. I then consider in detail mouthpart specializations for feeding (mostly involving the labiomaxillary complex), and place them in an evolutionary context. Whereas the digitate labrum of Perilampidae and Eucharitidae and the stoudy setose labrum of chrysolampine Pteromalidae are purported to be devices for filtering pollen grains from nectar, I conclude that they are not a feeding-related specialization whatsoever. I recognize seven functional types of mouthpart specialization relating to the extraction of floral nectar from long, narrow, tubular corollas (‘concealed nectar extraction apparatus’ [CNEA]) (Braconidae, Ichneumonidae, Leucospidae, Chrysididae), and postulate a transformation series for them. An eighth type of CNEA possibly occurs in Scoliidae. No such specializations occur in either Orussoidea, Trigonalyoidea, Megalyroidea, parasitoid Evanioidea, Stephanoidea, Cynipoidea, Proctotrupoidea, Ceraphonoidea or parasitoid Aculeata other than Chrysididae and Pompilidae. From examination of published cladograms I conclude that the evolution of CNEA has occurred several times independendy within the parasitoid Hymenoptera. So far as Ichneumonoidea are concerned, possession of CNEA is an autapomorphy for taxa at least below subfamily level. Possession of CNEA appears to be a synapomorphy for the family Leucospidae (Chalcidoidea) as a whole, and the same applies to the subfamily Parnopinae (Chrysididae). Hitherto not noted in the literature is the strong degree of evolutionary parallelism, with respect to CNEAs, between the Ichneumonoidea (Ichneumonidae, Braconidae) and the Aculeata (Chrysididae, Pompilidae, Vespidae [Vespinae, Masarinae, Eumeminae], Apidae, non-parasitoid Sphecidae). Also, Apocrita and Symphyta have two types of CNEA in common. Functional comparisons are made between the CNEAs of the parasitoids and those of other Hymenoptera. Compared to parasitoid flies, very few parasitoid wasps possess CNEA. Mouthpart specialization for conveying a nuptial gift of nectar or honeydew to the female occurs in the males of thynnine Tiphidae, while in the females of regurgitation feeders there is a trend towards reduction in labiomaxillary components, constituting a specialization for receiving and processing the gift. Mouthpart specialization for pollen feeding occurs in Mutillidae and Scoliidae. No mouthpart specialization for host feeding occurs in any parasitoid wasps, in contrast to parasitoid flies, despite host feeding being more common among the former. Sexual dimorphism in feeding-related mouthpart specializations is rare among parasitoid wasps; where it occurs, both sexes share the same type of CNEA, and the dimorphism is attributable to allometry.     

Food sources for adult Diachasmimorpha longicaudata, a parasitoid of tephritid fruit flies: effects on longevity and fecundity

We report the results of a study on potential food sources of the widely distributed Indo‐Australian braconid fruit fly parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae). Adults sustained life on diets of fruit juice or fruit pulp, a homopteran and its associated honeydew, or extrafloral nectary secretions. Longevities on all these foods and fecundity on fruit juice were comparable to those achieved on the honey that is typically provided in mass‐rearing programs. Certain of the flower species Bidens alba (L.), Spermacoce verticillata L., Lobularia maritima (L.) Desv., Brassica nigra (L.), Lantana camara L., their nectar or pollen, provided a diet that resulted in longer maximum life spans than water alone. Unlike some tephritid flies, the braconid did not feed on fresh bird feces or leaf‐surface exudates. Feeding by D. longicaudata on wounded host fruits of tephritid flies suggests that adult parasitoids would not need separate forays for adult food and oviposition sites, as these occur in the same locations. We conclude that an inventory of adult foods may help target inundative releases of D. longicaudata and lead to improvements in diets used for mass rearing.     

Covariation in life-history traits, demographics and behaviour in ischnuran damselflies: the evolution of monandry

The apparent erratic variation in life history traits, coloration patterns, and behaviours that exists among species within the damselfly genus Ischnura is shown to be interpretable when the species are partitioned into three groups. One group consists of species whose males are missing a pair of stout basal spines on the penultimate segment of their accessory penes. These are the only ischnurans in which males, by tandem guarding females, prevent sperm displacement. The other two groups can be recognized by the relative frequency with which mating occurs: monandrous species mate infrequently, polyandrous species more often. Compared to polyandrous species, monandrous species contain smaller size individuals, have greater sexual size dimorphism, have shorter duration copulations, do not have male biased operational sex ratios at aquatic sites, and are more likely to contain monochromatic females. Females belonging to the monandrous species tend to develop a characteristic form of pruinescence at maturity that obscures their underlying colour, and mature at a younger age. We propose that copulation serves only for sperm addition in monandrous species, for both sperm addition and displacement in polyandrous tandem guarding ischnurans, and for contact guarding as well as sperm addition and displacement in polyandrous species that do not tandem guard.