Indirect closing of the elytra in a cockchafer,Melolontha hippocastaniF. (Coleoptera: Scarabaeidae)

Abstract

TetheringWe used two sites for tethering: (1) the ventrite behind the middle coxae, which provided the firm basis for the pterothorax-fixed reference, and (2) the pronotum -only for demonstration of the flight. The holder was glued with the cyanoacrilate glue. Middle Accepted 17 February 2010 SUMMARY Actuation of the closing of the elytra was previously ascribed to intrinsic muscles in the mesothorax. We investigated closing (1) by loading or arrest of some thoracic segments in a tethered flying beetle, (2) by animation, i.e. passive motion of preparations of the thorax simulating the action of some muscle, and (3) by excision of some parts of sclerites or cuts across certain muscles. We found out that depression of the prothorax, necessary to unlock the elytra, precedes their opening but elevation of the prothorax is synchronous with the closing. The closing is retarded if the elevation is retarded by loading; if the elevating prothorax is clamped, then the closing is also arrested or hindered; animation of the elevation of the prothorax in the dead animal is enough for the closing of the previously spread elytra; the closing is prevented if a piece at the hind edge of the pronotum, positioned in front of the root of an elytron, is excised. This excision also prevents closing in the in vivo experiments. Mechanical interaction between the elytron and the prothorax is limited to the contact point between the posterior edge of the pronotum and the lateral apophysis of the root. Thus, the elevation of the prothorax is the indirect and main mechanism of the closing in Melolontha.Supplementary material available online at

Improvement of the aerodynamic performance by wing flexibility and elytra–hind wing interaction of a beetle during forward flight

“…So far, the closing and opening mechanism of elytra as well as their geometry have been the main focus in previous studies [18,19]. The elevation of the prothorax was speculated to be the main mechanism in closing the elytra [20]. A simple method for analysing the aerodynamic performance of elytra has been published [21,22].…”

Effect of microtrichia on the interlocking mechanism in the Asian ladybeetle, Harmonia axyridis (Coleoptera: Coccinellidae)

“…In a live beetle, it is impossible to open the elytra without causing direct damage to the tucked antero-medial edge of the elytron. To lock this connection, the meso- and metaterga must be drawn together with a special muscle [ 8 ]. Its antagonist bends the mesotergum forward, loosening the lock.…”

“…Why do the hindwings not slip outside? When the elytra lift, the hindwings are easily lifted along with the elytra, which spread actively at this moment due to the cooperative activity of meso- and metathoracic muscles [ 8 ]. In addition, the unfolding time of hind wings (0.24–0.55 s) is shorter than that of the folding time (≈3 s).…”

“…Various hindwing locking mechanisms have been found in beetles [ 7 ]. Beetle hindwing folding mechanisms are affected by many factors, including muscular [ 8 ], hydraulic [ 9 ], and elastic [ 10 – 11 ] properties. Some folding characteristics can also be described according to flexagon (or origami-type) folding in which all nodes conform to four angles, with an odd number of concave or convex folds [ 12 – 13 ].…”

“…Contact with the elytra and the abdomen [ 14 ] and the blocking of hindwings as the elytra closes in vivo also affect folding [ 15 – 16 ]. The extremely complicated wing-to-body articulation requires direct and indirect wing muscles [ 8 ].…”