On the Mouth-Parts and Mechanism of Suction in Schizoneura lanigera, Hausmann

Comparative morphology of part of the integumental fine structure of two Erythroneurine species: Singaporashinshana (Matsumura, 1932) and Empoascanarasipra Dworakowska, 1980 (Hemiptera, Cicadellidae, Typhlocybinae)

This study describes the fine structure of the mouthparts, antennae, forewings, and brochosomes of two leafhopper species belonging to the typhlocybine tribe Erythroneurini collected from the Karst area of Guizhou Province, southern China: Singaporashinshana, which prefers woody dicot hosts, and Empoascanarasipra, which feeds on grasses. As in other leafhoppers, the piercing-sucking mouthparts consist of a conical labrum, a cylindrical three-segmented labium, and a slender stylet fascicle. The labrum of both species has no sensilla and the labium has several common types of sensilla, but the two species differ in the numbers, types, and distribution of sensilla and in other aspects of the surface sculpture of the mouthparts. The stylet fascicle has distinctive dentition on both the maxillary and mandibular stylets. The antennae of the two species differ in several respects, including the sensilla and sculpture of the scape, pedicel, and flagellum, as well as the degree of sub-segmentation of the flagellum. Except for the variable scaly structure and rounded protrusions on the surface of S.shinshana, the fine structure of the forewing surfaces of the two species are similar to those of other leafhoppers. Only small spherical brochosomes were found on the body surface of S.shinshana and E.sipra. Similar studies of additional erythroneurine species are needed to determine whether differences in mouthpart and antennal fine structure may reflect adaptation to different host plant.

A previously unknown feeding mode in millipedes and the convergence of fluid feeding across arthropods

We report fluid feeding with a sucking pump in the arthropod class Diplopoda, using a combination of synchrotron tomography, histology, electron microscopy, and three-dimensional reconstructions. Within the head of nine species of the enigmatic Colobognatha, we found a pumping chamber, which acts as positive displacement pump and is notably similar to that of insects, showing even fine structural convergences. The sucking pump of these millipedes works together with protractible mouthparts and externally secreted saliva for the acquisition of liquid food. Fluid feeding is one of the great evolutionary innovations of terrestrial arthropods, and our study suggests that it evolved with similar biomechanical solutions convergent across all major arthropod taxa. While fluid-feeding insects are megadiverse today, it remains unclear why other lineages, such as Colobognatha, are comparably species poor.

The structure of extremely long mouthparts in the aphid genus Stomaphis Walker (Hemiptera: Sternorrhyncha: Aphididae)

Scanning electron microscopy and light microscopy were used to elucidate the morphology of labium and mandibular and maxillary stylets of the aphids Stomaphis quercus (L.) and S. graffii Cholodkovsky. The mechanism of labium shortening associated with feeding process was described as well. Stomaphis quercus and S. graffii have cone-shaped labium of 13 and 10 mm in length, respectively, that strongly extend behind the abdomen. The stylets bundle comprises a pair of mandibular and maxillary stylets which are on average as long as labium. Serial cross sections of labium revealed that the first segment is inverted inside and the second is pulled into it; both segments are shifted into abdomen. This study provides new information on S. quercus and S. graffii mouthparts that may help to understand their feeding behavior.

Studies on the Anatomy of Cimex lectularius. I

The anatomy of the bed-bug has been described many times by other writers. There is therefore no intention in the present paper of dealing with more than those parts of the anatomy which have been described incorrectly or insufficiently or have been omitted from the descriptions. Such are the mouth-parts, salivary pump, salivary glands and nephrocytes and with these subjects accordingly this paper deals exclusively.

The anatomy of the head and mouth parts of Psylla mali, the Apple sucker, with some remarks on the function of the labium

The investigation, of which the results contained in this paper are a part, was first commenced in 1910. It was then proposed to describe in some detail the entire anatomy of the adult insect, but when a measure of progress had been made, and the alimentary, tracheal, and nervous systems had been almost completed, the work was interrupted by my taking up an appointment in India. On returning to England in 1915, the enquiry was resumed for a short period at the end of the year, but early in 1916 it had to be abandoned again to meet the superior claims of entomological work with the Forces in Mesopotamia, for the War Office. This, and other investigations connected with problems which have arisen in England in consequence of the War, prevented any further progress being made, but, with the declaration of the Armistice it was felt that attention might once more be given to it. In the limited time which could be devoted to the work, it has not been possible to carry out the original plan of including the whole anatomy in one paper, and the description of the head and mouth parts has been selected because of the somewhat novel considerations which have arisen in connection with the latter, particularly with regard to the function of the labium during the operation of piercing, the publication of which it seemed undesirable to delav further.

Mouthpart morphology and stylet penetration of host plants by the glassy-winged sharpshooter, Homalodisca coagulata, (Homoptera: Cicadellidae)

The ultrastructural morphology of the mouthparts of the glassy-winged sharpshooter, Homalodisca coagulata, and method of plant penetration was examined using light microscopy, scanning electron microscopy, and transmission electron microscopy methods. The gross morphology of the labrum, labium, and stylet fascicle was consistent with what has been described for other plant-sucking homopterans. The ultrastructural examination of the mouthparts revealed unique details that have previously gone unreported. Several types of sensilla-like structures having the form of pegs and multi-lobed objects were identified on the outer surfaces of the labrum and within the labial groove. Dendritic canals terminated in an extensive network of smaller canals at the distal tip of the maxillary stylets below a series of surface denticles suggesting that this area may have a sensory function associated with locating xylem elements of host plants. Examination of salivary sheath pathways established that 65% of the plant penetrations by this insect terminated in the xylem vessels of the host plant. Probing by the insect was largely intracellular and terminal branching of a single probe site was common. Plant surface feeding sites varied with the stage of development which correlates with the depth of the xylem vessels and the length of the maxillary stylets of the various instars.

Anterior alimentary canal of the pear Psylla, Psylla pyricola foerster (Homoptera, Psyllidae)

Scanning and light microscopy investigations of the anterior alimentary canal of the pear psylla, Psylla pyricola Foerster (Homoptera: Psyllidae), revealed the morphology of the labium and stylets, as well as the presence of sensory structures and a valve in the precibarium. The labium consists of three telescoping segments with an internal labial groove, which surrounds and supports the stylet bundle. Also a part of the labial groove is the internal labial clamp. The stylet bundle is comprised of paired styliform mandibles and maxillae, which interlock to form the food and salivary canals. The stylet bundle proximal to the labium forms a large loop within a membranous crumena. When fully retracted the coiled stylets are under tension. Stylet extension generates increasing tension so that when retracted the stylets readily recoil within the crumena. Penetration of leaf tissues by the stylet bundle is dependent on the interaction between stylet muscles, opening and closing of the labial clamp, the barbed stylet tips, and the ventral position of the labium. Proximal to the crumena the paired stylets separate and diverge at the entrance of the precibarium, which is formed by the interlocking of the epi-and hypopharynges. There are 18 sensory structures in the precibarium, as well as a precibarial valve. These structures appear to be homologous to similar structures observed previously in aphids and leafhoppers. The morphology and the location of the precibarial sensilla suggest that, like the precibarial sensory organs of aphids and leafhoppers, they are gustatory and probably mediate acceptance or rejection of plant fluids, thus playing a major role in locating tissues for feeding.

THE RENEWAL AND REPLACEMENT OF THE STYLETS OF SUCKING INSECTS DURING EACH STADIUM, AND THE METHOD OF PENETRATION

In a study of the mouth parts of the scale and aphis, certain conclusions corresponding to those of Hermann Weber were independently drawn. While several phases of the subject need clarifying, it is definitely established that the retort-shaped organs at the bases of the stylets are masses of hypodermal cells constituting deep invaginations of the integument. Within these invaginations, which lengthen out in a circular manner during each stadium, new stylets are built up for each successive instar. In those members of the Hemiptera in which the head is deflected, the four stylets are separately coiled in the cephalic region and at a definite stage during each ecdysis the new stylets pass down to take the place of the old which are discarded at the moult.The manner of this renewal and replacement of the stylets appears to be, in many respects, unique. But, inasmuch as the stylets are simple hollow chitinous structures, they may be said histologically to bear a closer resemblance to other cuticular processes than they do to the more complex organs arising from imaginal buds during metamorphosis. An analogy to the renewal of the stylets is presented in the development of the spines and hairs of the body. The methods whereby the coiled stylets are expelled from the head are discussed.The action of the protractor muscles in the aphis and scale is altogether inadequate to explain the means of penetration into the compact tissues of woody growths. More especially is this the case where the stylets are much longer than the labium, and are, moreover, looped within the body and thus neutralize the effect of muscular action at the base. New facts are advanced to supplement those already known, and it is submitted that the stylets are propelled forward by successive short holds contrived by the joint action of the labrum and labium. In the aphis the main function of the stylet muscles is directional control of the tips, enabling a short stylet to explore a large area. The absence of this control in the scale is compensated for by the provision of longer stylets. Directional control permits of selective feeding, giving rise to a sense of taste. This is manifest in specific types of injury to the host plant and also by a modification in the insect of accessory structures of the mouth.