ON THE STRUCTURE AND FUNCTION OF THE HIND SPIRACLES OF THE LARVA OF THE BEETLE DON ACIA (COLEOPTERA, CHRYSOMELIDAE)

Abstract

THE early stages of a number of different insects live in mud and obtain their supply of oxygen by piercing the roots of plants with their specially modified spiracles. I n a previous paper (Varley, 1937) it was shown that the sharp piercing spiracles of the larvae of the flies Clarysogaster (SYRPHIDAE) and Notiphila (EPHYDRIDAE) have openings close to their tips so that by piercing a root a larva a t once puts its tracheal system in direct connection with the gas in the intercellular spaces in the root, which, as Ege (1915) has shown, may contain up to 12% of oxygen. The larvae of the Chrysomelid beetle Donacia semictcpea Pz. live side by side with these fly larvae, and they also pierce the roots with their strong hook-like hind spiracles. It seemed curious then that in the most recent detailed account of the spiracles of Donacia (Boving, 1910) it was concluded that the functional spiracular openings were not in such a position that they could be inserted into the roots, but were at the very base of the hooks. The opinion was therefore expressed (Varley, 1937) that certain apparent slits in the hooks, which were considered by Boving to be covered over by thin membranes, might be the true spiracular openings, and enable the spiracles to function in the same way as do those of the fly larvae already mentioned. Ege (1915) makes the same suggestion. I n 1938 I had the great pleasure of meeting Dr. Boving, and he encouraged me to reinvestigate the structure and function of these specialised spiracles.The larvae of Donacia (figs. 1, 5) were first described by Kunze (1818) and since then the structure of their spiracles has been studied by a long succession of workers, notable amongst whom are Schmidt-Schwedt (1887, 1889)) Dewitz (1888)) Sanderson (1900), MacGillivray (1903), Boving (1906Boving ( , 1910 and Deibel(l910). That the peculiar spiracular hooks on the eighth abdominal segment are concerned with respiration has been generally agreed, and that the tips of the hooks are actually inserted into the roots of the plants on which the larvae feed was noted by von Siebold(l859)and confirmedby the careful observations of Schmidt-Schwedt (1887) and has not since been disputed. However, no two authors seem to have been in agreement as to the way in which the hooks function as spiracles, and there is considerable dispute as to the interpretation of their structure.Most authors are agreed that in the fully grown larva each spiracular hook contains two pairs of air-filled chambers which are separate over the greater part of the length of the hooks, but whereas Schmidt-Schwedt (1889) and Deibel (1910) considered the upper and lower chambers to be separated incompletely from one another, MacGillivray (1903), Sanderson (1900 and Boving (1910) believed the partition between them to be complete, though Sanderson thought that the membrane between them might act as a gill. Deibel, Schmidt-Schwedt and Sanderson found that the upper paired chambers communicated with the outside by longitudinal slits, but MacGillivray and Bovin...

DONACIA AUSTRALASIAEBLACKBURN: THE SOLE REPRESENTATIVE OF THE SUBFAMILY DONACIINAE (COLEOPTERA: CHRYSOMELIDAE) IN AUSTRALIA AND NEW GUINEA

“…The following combination of characters is diagnostic within the Australian Chrysomelidae: Adult: elongate, with relatively long legs and antennae (vide Gressitt 1971, Fig. 1); head prognathous; eyes prominent, strongly convex and without excavate internal margins; frons without Xor H-shaped grooves; antennae inserted ca 1.5 socket diameters apart, halfway between eyes and midline; antennae longer than 0.67 body length; pronotum without lateral borders; fore coxae prominent, conical, prosternal process reduced to fine ridge between them; hind femora swollen in apical half, maximum width ca 0.2 length, without ventral teeth; tarsal claws simple; venter covered in dense recumbent pubescence; first ventrite as long as next 3 together; Larva: head capsule with 5 pairs of pigmented eye-spots but without morphologically distinguishable stemmata; labrum free; galea and lacinia modified into stylets; body without differentiated xlerites; spiracular atria of eighth abdominal segment modified as long, ventrally produced, canaliculate hooks (Varley 1939). Adults and larvae both feed on aquatic plants, the larvae being submerged.…”

“…Donaciines are common insects in the Northern Hemisphere, therefore there is an extensive literature concerning biogeography (Monr6s 1959;Borowiec 1984;Askevold 1990a, b), life history and larva (Hoffman 1939;Medvedev and Zaitsev 1978;Lee 1991), palaeontology (Askevold 1990b), catalogue of species and host plants (Borowiec 1984), internal anatomy (Mann and Crowson 1983;Brivio and Balsbaugh 1984;Askevold 1988), and physiology (Varley 1939;Houlihan 1969).…”