Merope tuber (Mecoptera): A Wing-body Interlocking Mechanism.
Psyche 81(2):303-306, 1974.
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MEROPE TUBER (MECOPTERA) :
A WING-BODY INTERLOCKING MECHANISM
BY T. F. HLAVAC~
Museum of Comparative Zoology
Cambridge, Massachusetts 02 I 38
As an insect pushes its dorsal surface against obstacles while -
moving through a substrate, the wings will tend to be forced apart. In many Coleoptera, such divergence is prevented by a complex of devices interlocking the elytra with the thorax and abdomen. A common interlocking mechanism involves intermeshing of parallel arrays of setae angled towards the potentially disrupting force (Fig. 2). A similar high friction binding system on the mesojugum and metascutellum of Merope tuber provides additional evidence for the ground dwelling habits of this rare mecopteran. The fore-jugal lobe of Merope is highly modified relative to its counterpart on the hind wing and as compared with the jugal regions of other panorpoids (Fig. I ; JL2, JL3). It does not bear setae and does not appear to function in wing coupling. More importantly, the mesojugal lobe is much thicker, more heavily sclerotized than the wing proper, is quite rigid, yet capable of slight movement about the third anal vein, but does not fold over as the wing comes to rest. The ventral surface is completely covered with uniformly small (.oo~ X .003 mm) flat topped carinae, angled posteriorly and organized in rows perpendicular to the long axis of the wing (Figs. I, JL2; 3, 4). The metascutellum bears two patches of anteriorly projecting ridges about twice as long (.017 X .003 mm) but about as high as those on the fore wing (Figs. I, R, S3; 5). In rest position, the jugal lobes lie close together and directly above the striate metathoracic areas. When so placed, a small ventral movement will cause the slanting nearly parallel ridges to intermesh. Two functions, which may be combined, may be served by the jux- traposition of parallel carinae: stridulation and interlocking. Stridu- lation is an unlikelv function for these structures. As the wing -
moves medially to rest, the ridges move parallel to one another, not 'Research supported by NSF grant GI3 31173, F. M. Carpenter, Harvard University, Principal Investigator. Manuscript completed at Cornell where E. H. Smith kindly made necessary facilities available. Manuscript received by the editor June 15, 1974.
Figs. 1-2. Wing-body interlocking mechanism of Merope. Fig. 1. Left half of pterothorax, dorsal view.
As the fore-wing moves medially (a) ;
parallel ridges, indicated by two heavy lines, on the jugal lobe (JL2), and on the metascutellum (R, 83) are brought into contact. Fig. 2. Model of interlocking system, posterior view. Small arrow (a) indicates direction of emplacement as wing comes to rest, see Fig. 1; large arrow (b) the direc- tion of intermeshing of the slanted ridges. lA, 2A, 3A, anal veins; JL2, JL3, meso- and metajugal lobes; R, ridge bearing patch of metascutellum, S3; a, direction of wing movement; b, +direction of interdigitation. perpendicularly as in many sound producing structures (Fig. 2, a). Stridulatory mechanisms are not known in Mecoptera (Riek 1967). The geometry of ridge interdigitation, however, is precisely that required to resist postero-lateral wing displacement during locomo- tion within a substrate or interstitial spaces. The unique jugal lobe and metascutellar structures of Merope may serve then as a wing- body interlocking mechanism which increases structural integrity during crawling within a matrix.
Other structural features and meagre biological data suggest that Merope is a substrate inhabitant not a surface dweller as are other winged Mecoptera. The body is dorso-ventrally flattened ; the pleural axes of the undifferentiated thoracic segments are sharply inclined from the vertical (Mickoleit 1967). The fore wing is somewhat tegmenized, being thicker and more heavily sclerotized than the hind wing. Antennae and legs are short; pterothoracic appendages may operate almost entirely within the outlines of the flattened wings. Little membrane is exposed between tagmata and between abdominal segments. These characters result in greatly reduced cross section area
Hlmac -Merope tuber 305
during locomotion and improved structural integrity relative to other panorpoids. Some specimens have been taken under logs or stones, as were the only known examples of Austromerope. The photographs in the original description (Killington 1933) show that the jugal lobe of this Australian form is similar to that of Merope in size and shape. Several lines of evidence point towards a marked divergence of meropeids from surf ace dwelling, loosely constructed configura- tions of related taxa.
The transformations required to derive Merope from a generalized mecopteran are parallel and analogous to those hypothesized for the very early evolution of substrate dwelling Coleoptera (Hlavac 1972). The ability to keep flexible wings in place under stress through inter- locking devices is an obvious precursor for the development of elytra. Meropeids may then represent an attempt, albeit a feeble one, by another holometabolous lineage to occupy the substrate adaptive zone. HLAVAC, T. F.
1972. The prothorax of Coleoptera: origin, major features of variation. Psyche. 79 : 123-149.
KILLINGTON, F. J.
1933. A new genus and species of Meropeidae (Mecoptera) from Australia. Ent. Mon. Mag. 69: 1-4.
1967. Das thoraxskelet von Merope tuber Newman (Protomecoptera). 2001. Jb. Anat. Bd. 84: 313-342.
RIEK, E. F.
1967. Structures of unknown, possibly stridulatory, function on the wings and body of Neuroptera with an appendix on other En- dopterygote orders. Aust. J. 2001. 15: 337-348.
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