Structure and ecdysial process of the larval spiracles of the scarabaeoidea, with special reference to those of Lepidoderma

Abstract

The structure of the larval spiracles of the scarabaeid beetle, Lepidoderma albohirtum Waterh., has been examined by means of serial sections and stereoscan electron micrographs of whole and dissected specimens. Gas exchanges with the ambient atmosphere are effected through aeropyles in the spiracular plate. The aeropyles are of two types: (1) slit-like aeropyles about 4 � long and 0.1-0.5 � wide; and (2) round or oval aeropyles that are usually about 0.2-0.3 u wide. The ecdysial tube is often open in preparations, and this has led to the commonly expressed view that it is the chief or only opening into the spiracular atrium. The open condition of the ecdysial tube in preparations is an artifact. The formation of a new spiracle is briefly described. Cuticular struts project inwards from the peritreme and branch at their apices. Then the apical branches divide and those from different struts anastomose to form the plate and the network immediately below the plate. All of these structures are secreted by very long cytoplasmic projections. The nuclei of the epidermal cells remain in the region of the peritreme and do not enter the main columns of cytoplasm that in due course secrete the cuticular struts. The cytoplasmic columns that form the largest struts consist of projections from many epidermal cells. The chief differences in the structure of the spiracles within the superfamily Scarabaeoidea are briefly noted. A closing apparatus is present in the Trogidae, Lucanidae, Passalidae, and Glaphyrinae but is absent in the Geotrupidae and Scarabaeidae. The ecdysial process in primitive Scarabaeoidea is of the typical elateroid type, whereas specialized Scarabaeoidea have a bulla that carries the ecdysial tube. The modified elateroid process of specialized forms is here named the pseudopanorpoid type. The spiracles of some species of Trox are biforous. Those of other species of Trox and all other Scarabaeoidea examined are cribriform. The cribriform type of spiracle has been evolved on at least two occasions within the superfamily.

Differences in penetration routes and establishment rates of four entomopathogenic nematode species into four white grub species

“…The cribiform spiracles of white grubs are covered with sieve plates punctured by aeropyles the diameter of which, as measured in third instars of selected white grub species (Hinton, 1967;Galbreath, 1976;Forschler and Gardner, 1991), is several times smaller than the diameter of even the smallest IJs, thus making penetration through the spiracles unlikely (see Section 4).…”

Spiracle structure and function inCostelytra zealandicalarvae (Coleoptera: Scarabaeidae)

“…The structure of the spiracles of scarabaeid larvae has been described in detail by Lotz (1962) and Hinton (1967). The external structure consists of a central bulla surrounded by a smooth, crescentshaped spiracular plate pierced by a number of fine slits or aeropyles (about 200 in 3rd-instar C. zealandica larvae, each about 5 ftm long and 0.2 /xm wide) which are the only openings into the tracheal system.…”

“…Some authors (e.g., Buck 1962, Hinton 1971) have stated that the rate of diffusion through slit-shaped apertures of insect spiracles is in proportion to the perimeters rather than the areas of the apertures, because of the 'pore diffusion' effect of Brown & Escombe (1900). It has been pointed out many times in botanical literature (see, e.g., Cowan & Milthorpe 1968) that this effect was postulated under the false assumption that the rate of diffusion through pores is determined solely by the size and shape of the pores themselves.…”

“…Scarabaeid larvae live in soil in an environment which is normally humid and occasionally waterlogged, and their spiracles, like those of many other insect larvae from humid environments, lack a closing apparatus (Hinton 1967). This paper describes the structure of the spiracles of Costelytra zealandica (White), and presents the results of experiments testing the effect of the lack of a closing apparatus on the transpiration rate, and the effectiveness of the protection of the spiracles against flooding by water.…”

Respirometry techniques for terrestrial invertebrates and their application to energetics studies

“…The frequency and duration of the 'spiracles open' period is dependent on -if not controlled by-the partial pressures of oxygen and carbon dioxide within the tracheal system, and therefore indirectly on the concentrations of these gases in the atmosphere (Schneiderman 1960, Kanwisher 1966. P. ephippiata represents a family of insects that have no spiracular valves in the pre-imaginal stages (Hinton 1967), so the (albeit irregular) cyclic nature of its larva's carbon dioxide emissions is noteworthy. When the partial pressure of carbon dioxide was low (c.8ppm), i.e., scrubbed air in the IRGA, the peaks representing emissions of respiratory carbon dioxide were more frequent, more regular, and of a higher amplitude than those obtained when larvae were in normal air (c.33Oppm CO 2 ).…”