DEVELOPMENT OF THE POSTERIOR SPIRACLES IN HYPODERMA (DIPTERA: HYPODERMATIDAE) LINEATUM AND H. BOVIS

Each posterior spiracle is generally divided into three main parts—posterior spiracular plate, fell and spiracular chambers. The characteristic features of these parts and the moulting processes during the development of the larvae are described in the text. The main features in the development of the third instar larva are the replacement of the epidermal cells by chitin, shortening of the felt chamber and sear cord, increase in the depth of the spiracular chamber, gradual melanization of the posterior spiracle, and then its separation from the dorsal longitudinal trunk prior to pupation.

The structure of the Spiracles of the cattle tick, Boophilus microplus

The structures of the nymphal and adult spiracles of the tick, Boophilus microplus, have been examined by means of serial sections and a stereoscan electron microscope. Contrary to the views of recent writers, the functional openings of the spiracle have been found to be holes or aeropyles in the peripheral part of the spiracular plate of the adult tick. The ostium of previous writers is shown to be the ecdysial tube, which is present only in the spiracles of adult ixodid ticks. After the nymphal-adult ecdysis, the ecdysial tube is closed. There is thus no ostium in this stage, as has been claimed by previous writers who supposed that the chief or only route for gas exchanges between the atrium of the spiracle and the ambient air was through the so-called ostium. The ecdysial process of the spiracles of ticks is shown to be basically similar to the ecdysial process of the spiracles of certain insects such as scarabaeid larvae and the larvae of some Diptera-Cyclorrhapha.

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

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.