Mesothoracic Skeletomusculature and Mechanics of Flight and Jumping in Eupelminae (Hymenoptera, Chalcidoidea: Eupelmidae)

Abstract

Mesothoracic skeletomusculature of male and female Eupelminae is described and compared with that of other Eupelmidae, Chalcidoidea, and Hymenoptera. Various external mesopleural features and structural dimorphism between the sexes are explained by differences in muscle form and placement. A set of terms for mesothoracic structure is proposed that is equally applicable to male and female eupelmines and to other chalcidoids. Mechanics of flight and jumping in male eupelmines, and of jumping in females, is also described. The flight mechanism of males is similar to that previously described in other hymenopterans and is structurally independent of the jumping mechanism. Contraction of large mesotergal-mesotrochanteral muscles, originating from the axillae and axillar phragmata, act directly to retract the mesotrochanters into the mesocoxae for jumping. Females have coadapted the flight and jumping mechanisms into a single mechanism to improve jumping greatly. The mesotergal-mesotrochanteral muscles are reduced to slender, tendon-like muscles originating from the anteroventral angle of each lateral axillar surface. Jumping in females results from contraction of large mesopleural-mesotergal muscles that insert into anterolateral processes of the mesoscutum by pads of resilin. The pads are stretched during contraction of the mesopleural-mesotergal muscles and the potential energy thus stored is subsequently released to flex the mesonotum along the transscutal articulation. The first and second axillary sclerites are modified to function as a hinge to control mesonotal flexing for jumping. Flexing the mesonotum rotates the lateral axillar surfaces anteriorly and dorsally, thereby pulling up on the mesotergal-mesotrochanteral muscles and changing a horizontally directed force into a vertical force that is used to retract the mesotrochanters for jumping. A mesothoracic lock mechanism to prevent initial mesonotal flexing is proposed, but is not documented. “Contortion” of female eupelmines is described, and is a consequence of the increased degree of mesonotal flexing required for their jumping mechanism. The modified mesocoxal articulation of females is hypothesized to function in rotating the middle legs cephalad to protect the head and antennae during landing. It is questioned whether female eupelmines can fly, and the adaptive significance of enhancement of jumping at the expense of flight in females, and of sexual dimorphism in the subfamily, is discussed.

Description of three new genera and four new species of Neanastatinae (Hymenoptera, Eupelmidae) from Baltic amber, with discussion of their relationships to extant taxa

“…However, the posterior margin of the scutellum is advanced slightly anterior of the posterior margin of the dorsellum when the mesonotum is fl exed so that both a horizontal dorsal and the vertical posterior surface of the dorsellum is visible (Gibson 1008, fi g. 35). Th e anterior movement of the posterior margin of the scutellum is a functional consequence of raising its anterior margin during mesonotal fl exing, which reduces the length of the mesonotum (Gibson 1986). Th e scutellum extends to the base of the propodeum over a medially very thin metanotum in Savzdargia (Figs 67,68: no 3 ) and other Encyrtidae (Noyes 1997, fi gs 11-18), even when the mesoscutum is fl exed (Noyes 1997, fi g. 13).…”

“…Th is is because female Eupelminae and both sexes of Neanastatinae, Encyrtidae and Tanaostigmatidae share similar suites of conspicuously modifi ed mesosomal features, whereas male Eupelminae exhibit mostly plesiomorphic features that closely resemble Cleonyminae, and some genera of Calosotinae are intermediate in structure between the two extremes (Gibson 1986(Gibson , 1989. Th e similar suites of apomorphic features are thought to constitute functional-structural complexes to improve jumping ability and consist of structures that are modifi ed either to increase power for jumping or to protect the body from the greater forces involved in jumping (Gibson 1986). Putative autapomorphies support the monophyly of Encyrtidae and Tanaostigmatidae sensu stricto (see Gibson 2008) but not Eupelmidae (Gibson 1989).…”

Synopsis of Bradepyris Kieffer, 1905 (Hymenoptera, Bethylidae, Mesitiinae)

“…The terminology of body structures generally follows Barbosa & Azevedo (2009, 2011), DuPorte (1965, Evans (1964), Gibson (1986), Mikó et al (2007), Móczár (1970), Richards (1977) and Ronquist & Nordlander (1989).…”

The backward jump of a box moss mite

“…Leaping box moss mites are the only known example of legjumping arthropods with soft and extensible bodyŝ ternum articulation (other leg-jumping arthropods that possess a foldable thoracic region are female chalcid wasps (Gibson 1986), but their body^sternum articulation is less extensible than that in Indotritia cf. heterotrichia).…”