Seventh Sternite Research Articles

Unique Morphogenesis in the Damp-Wood Termite: Abscission of the Stylus during Female Reproductive Caste Differentiation.

Eusocial insects organize their colonies based on division of labor and caste differentiation, in which caste-specific morphologies are sculpted during postembryonic development. In the differentiation between reproductive and sterile castes, characteristics related to mating and reproduction are developed in reproductives, and degenerated in neuters, although little is known about the developmental regulations during the differentiation. In some species of termites, a sensory protrusion at the posterior end of the abdomen, the stylus, is known to disappear in female reproductives. In the present study, we performed anatomical and histological analyses in the damp-wood termite Hodotermopsis sjostedti to elucidate the developmental process underlying the disappearance of the stylus during neotenic and alate differentiation. Although it was first hypothesized that styli were hidden beneath the enlarged seventh sternite, our observation results found out that the styli were completely lost in reproductive females. Further histological observations revealed that the stylus disappearance was not accomplished by degeneration process; rather, styli were separated from the abdomen and discarded with the exoskeleton (exuviae) during the molt into the reproductive caste. This phenomenon in which live tissues are discarded through developmental processes is suggested to be a case of abscission, as seen in plant leaves.

Hoplonannus australis sp. nov. (Hemiptera, Schizopteridae): amended diagnosis of the genus and first record from South America.

Hoplonannus McAtee Maloch, 1925 comprises three species described from Central America. Females of all these species are known only from brachypterous specimens. This paper describes the first South American species of the genus, Hoplonannus australis sp. nov. The new species differs from its congeners, in females, by the submacroptery, presence of ocelli and a basal bulge in the seventh sternite; in males, it differs by the presence of a process in the eighth tergite and the right paramere bifurcate apically, with branches subparallel. These traits entail a new diagnosis for the genus.

Laboratory Demonstrations of Pheromone-Mediated Scent-Marking, Orientation, and Mounting Behavior in Polistes exclamans (Hymenoptera: Vespidae)

A combination of arena,Y-tube olfactometer, and flight tunnel assays were used to determine responses of male and reproductive female Polistes exclamans Vierick (Hymenoptera: Vespidae) to odors and extracts of conspecific males and females, as potential pheromone-mediated sexual behaviors. Males rubbed the sternites of the gaster on filter paper in response to extracts of the female mesosoma and gaster, indicating possible scent-marking. In a Y-tube olfactometer, females oriented to extracts of the male head, gaster, legs, seventh sternite, and mandibular glands. In the olfactometer, males oriented to extracts of the female whole body, but were repelled by extracts of the female head. Both females and males oriented to solvent washes of glass jars that held wasps of the opposite sex, as well as volatile collections from the opposite sex. In a flight tunnel, males and females both exhibited chemoanemotaxis that consisted of upwind flight and close range casting in response to odor piped into the tunnel from live wasps of the opposite sex. Males mounted a female wasp model treated with an extract of the female mesosoma. Together, these experiments suggest pheromones stimulate male scent-marking, attraction of females to males and males to females, and mounting, in P. exclamans. Results indicate the mesosoma as a source of female pheromones, and the legs, gastral sternal glands, and mandibular glands, as male pheromone sources.

The first report of gynandromorphy in termites (Isoptera; Kalotermitidae; Neotermes koshunensis).

This is the first report of gynandromorphy in Isoptera. An Asian dry-wood termite, Neotermes koshunensis (Shiraki) [Kalotermitidae], possessing both male and female phenotypic characteristics, was found on Okinawa Island, Japan. This deformed individual showed morphological and anatomical hermaphroditism in the abdomen. The right side of the seventh sternite was the female form and contained an ovary, while the left side was the male form and contained a testis. Genotypic analysis revealed that this individual was a genotypic bilateral chimera. These results suggested that the termite was a bilateral gynandromorph with a male left side and a female right side. As reported previously in other insects, double fertilization (by two sperms, one with an X and one with a Y chromosome) of a binucleate egg is the most likely mechanism that generated this genotypic bilateral chimera. N. koshunensis has the ability to reproduce through parthenogenesis, in which the secondary polar body is likely to be used for nuclear phase recovery. If the second polar body in this mechanism has high fertility and healthy embryogenic potential, like an egg nucleus, some of gynandromorphs might be produced by a side effect of parthenogenetic ability.

The transition path from female workers to neotenic reproductives in the termite Reticulitermes labralis.

Termite workers are characterized by unique flexibility in that a worker can develop in one of three ways: remain a worker, become a soldier within two successive moults, or become a neotenic reproductive (NR) within a single moult. However, is it true that workers can transform into NRs within a single moult? Actually, the developmental pathways of workers turning into NRs remains unclear. In this study, we show for the first time that the female workers of Reticulitermes labralis develop into NRs after a pre-NRs stage. We found that a female worker became a NR after two successive moults, whereas the male workers copulated directly with queens without undergoing any moults. After the first moult led the female workers into the pre-NR stage, the length of their abdomens, seventh sternites and ovaries significantly increased. After the second moult from the pre-NRs stage into NRs, the follicle cells returned to normal, and a few oocytes and follicle cells underwent apoptosis. These results demonstrated that the female pre-NR type was a transitional type during the development of female workers to the NR caste, and the starting point for oogenesis resumption was the NR stage. We confirmed there were fundamental differences in the reproductive pathway of the male and female workers. Therefore, we determined that the transformation process of the female NRs from workers may be a very complex process, and the reproductive biology of the workers has great potential to provide important and spectacular insights into the evolution strategy of termites.

Polymorphism in the neotropical termite Serritermes serrifer

AbstractSerritermitidae (Isoptera) is a small and little known Neotropical termite family which includes only two genera: Glossotermes and Serritermes. Despite the lack of detailed studies, it has been assumed that these termites have a true worker caste. A recent study revealed that Glossotermes has a linear development pathway and lacks true workers. Here, we present a study of the polymorphism of Serritermes serrifer Hagen & Bates, a species endemic to the Cerrado ecoregion of central Brazil which lives as an inquiline inside nests of Cornitermes spp. A morphometric analysis was performed based on measurements taken of 11 body parts of 544 specimens of immatures, worker‐like individuals, soldiers, and alates. Sex of specimens was determined by dissection and examination of the seventh sternite. A principal component analysis (PCA) was used to evaluate morphological changes during development. Contrary with previous information from the literature and similar to Glossotermes, Serritermes shows a linear development pathway with two larval instars, two sizes of pseudergates, and a single nymphal morph. Pseudergates apparently undergo stationary molts. Sex ratio among pseudergates is male‐biased, but not as strongly as in Glossotermes. Typical colonies have a single physogastric primary queen and a single primary king. Ergatoid reproductives are relatively rare and some female ergatoids may become strongly physogastric. Nymphoid reproductives were not found. All soldiers are male and bear well‐developed testes.

Refinement of Methods for Sexing Instars and Caste Members in Neotermes koshunensis (Isoptera, Kalotermitidae)

Exact sexing of individuals is important to an understanding of termite societies. We found that the female-specific sexual character of the elongated seventh sternite, known in other termites, is useful for distinguishing the sex of individuals of the dry-wood termite Neotermes koshunensis (Shiraki) from the fifth instar onward. The method described is highly efficient at sexing instars, nymphs, soldiers and alates.

Sexual Dimorphism in North American Coccinellids: Sexing Methods for Species of Coccinella L. (Coleoptera: Coccinellidae) and Implications for Conservation Research

Coccinellids typically do not show exaggerated sexual dimorphisms, and the only reliable sexing methods for some species have been dissection and behavioral observations. Behavioral methods can potentially lead to sex identification but are very time consuming, require exposing sexually naïve individuals to conspecifics, and risk incorrect identification since homosexual mounting in these species has been observed in the laboratory. Research involving use of live specimens requires techniques to non-invasively determine the sex of individuals, but such methods have not been clearly or fully described in the literature. Closer examination of the species Coccinella novemnotata Herbst, Coccinella septempunctata L., Coccinella transversoguttata richardsoni Brown, and Coccinella trifasciata perplexa Mulsant has led to the discovery of a reliable and efficient way to differentiate the sexes by looking at the shape of the seventh sternite (fifth visible), and this method has been demonstrated to be 100% reliable for all four species. Another, even more rapid, method uses the shape of a prominent black pronotal marking and shows promise for C. novemnotata but is not applicable to the other species. Additionally, most species of Coccinella L. have males with conspicuous pale anterior coxal spots and femoral stripes that can be easily viewed, especially on mobile specimens. Morphometric data that quantify external dimorphisms and provide evidence for the reliability of using them for sexing are reported. All known external characters that can be used for sexing North American Coccinella species are consolidated for easy reference. The significance of these findings for research into the decline of native Coccinella species in the United States is discussed.

Defensive Glands of the Darkling BeetleMesomorphus villigerBlanchard (Coleoptera: Tenebrionidae)

Massive home invasion by the darkling beetleMesomorphus villigerBlanchard 1853 (Coleoptera: Tenebrionidae) during monsoon season make it a nuisance pest in many regions of south India. Morphology of defensive glands and mode of release and dispersal of the defensive secretion were analysed. Defensive glands were separated from the abdominal sternites by cutting along the posterior margin of the seventh sternite. Glands are evaginations of intersegmental membrane between the seventh and eighth sternites consisting of two long sac-like reservoirs, and glandular secretion is released by exudation and spread through epipleural gutter of elytra. Gradual release of the secretion is a strategy to repel the predators for a longer duration.

Marsupial extension in terrestrial isopods (Crustacea, Isopoda, Oniscidea)

In Oniscidea, the marsupium is a ventral pouch where the offspring develop independently of an external water source. The marsupium is formed by five pairs of overlapping oostegites that develop in the females during their reproductive period. In this study, ovigerous females of 35 species were dissected, their oostegites were extracted, and the intra-marsupial offspring were counted. Two marsupium forms were recognized: distended, in which the oostegites protrude distally in relation to the sternites; and non-distended, in which the oostegites are parallel to the sixth and seventh sternites. Armadillidium nasatum, A. vulgare, Pudeoniscus birabeni, Circoniscus gaigei and Cubaris murina, conglobating species with a non-distended marsupium, and Neotroponiscus daguerri and N. carolii, non-conglobating species with a distended marsupium, have a concavity on the ventral floor of the 6th and 7th pereionites, here called the marsupial extension. This is the first record of a marsupial extension which extends beyond the area formed by the oostegites in Oniscidea.

A new species of Chaerilus Simon, 1877 (Scorpiones, Chaerilidae) from China

A new species, Chaerilus mainlingensis sp. nov., is described from Xizang in China. The present new species is distinguished from the congeners by chela with width/length ratio more than 2.4, seven rows of denticles on fixed and movable fingers of pedipalp chelae, three or four pectinal teeth in females, and almost smooth teguments of the seventh sternite and all of the metasomal segments.

Sexing the “drop-drop” beetle, Psiloptera pertyi (Coleoptera: Buprestidae)

The sexual description of adult Psiloptera pertyi was carried out through observations of their external morphological characteristics. Males have their first five abdominal sternites, as well as the seventh and eighth, strongly sclerotized. Females have a similar morphology except the eighth abdominal sternite is not sclerotized. Males have a prominent apex on the seventh sternite, while females have a deep incision in the apical margin of the same segment. Males also have a triangular incision en the extreme posterior margin of the fifth sternite; in females, this segment is rounded. The number and form of the abdominal sternites should be taken into account for sexing adults of P. pertyi.

Structure of the stridulatory apparatus and analysis of the sound produced by Smicronyx fulvus and Smicronyx sordidus (coleoptera, curculionidae, erirrhininae, smicronychini).

Wing folding spicules, elytral binding patches, and elytral locking devices of adult male and female seed weevils, Smicronyx fulvus LeConte and S. sordidus LeConte, involved in stridulation are described. Sound is produced by both sexes of the two species when the plectrum, paired conical teeth located along the anterior margin of the dorsally elevated seventh sternite, is struck against an elongate file, the pars stridens, on the under surface of the apical portion of each elytron. A second plectrum, on the sixth tergite, is well-developed in males of both species and is used by males to produce sound before and during mating. Sex-specific and species-specific differences in the sound produced is attributed to structural variation in the pars stridens and the elytra. The pars stridens determines frequencies, while the elytra may further modify the sound. The frequency range for male S. fulvus is 1,000 cycles per second (cps) through 13,000 cps and for male S. sordidus is 2,500 cps through 13,000 cps. The frequency range for female S. fulvus is 2,000 cps through 11,500 cps and for female S. sordidus is 900 cps through 11,500 cps.

A REVISION OF THE GENUSTACHINUS(COLEOPTERA: STAPHYLINIDAE) OF NORTH AND CENTRAL AMERICA

AbstractThe species of the genusTachinus(Staphylinidae: Tachyporinae) of North and Central America are revised. Forty-four species are recognized, of which eight are described as new; eight species names are placed in synonymy. The subgeneraDrymoporusThomson andPorodrymusRey are placed in synonymy withTachinusand the genus is divided into 17 species groups based on an examination of both the Nearctic and the Palearctic fauna. The distribution of each species is mapped and the male genitalia, the male and female eighth abdominal sternites and tergites, and the male seventh sternite are illustrated for every species. A neotype is designated forT.fumipennisSay, and lectotypes are designated for all the North and Central American species ofTachinusdescribed by Gravenhorst, Erichson, Mäklin, Horn, and Sharp. Diagnostic keys for males and females are included. A brief discussion of the nomenclatural history of the genus, of collecting techniques, and of the major diagnostic characters is included.

クロゴキブリ幼虫期の雌雄判別

The morphological characteristics in the terminal part of abdomen of Periplaneta fuliginosa (Serville) were studied from the newly emerged first instar nymph through the whole developing stages until adults. Except the first instar nymphs which were obtained escaping from the oothecae the specimens used for the present observations were collected by the bait traps set in a building. The morphological changes which took places during the course of developing could be traced into two directions, that is, one to female adult and another to male adult. The presence and the developing of a notch at the middle of hind margin of the ninth abdominal sternite as well as the styli growing on the ninth sternite, and the striking development of the seventh sternite were noticed in the specimens developing to females. With the specimens growing to males no notch was observed at the margin of the ninth sternite and either the eighth, the ninth sternites or the styli remained unreduced while developing. These characteristic features enabled the sexing of cockroach through the whole developing stages.

6-Alkyl-1,4-naphthoquinones from the defensive secretion of the tenebrionid beetle, Argoporis alutacea

The abdominal defensive glands of the western American tenebrionid beetle, Argoporis alutacea, contain a viscous mixture of 6-methyl, ethyl-, propyl-, and butyl-1,4-naphthoquinones as well as the usual tenebrionid 1,4-benzoquinones. The naphthoquinones were isolated by preparative gas-liquid chromatography (GLC) and their structures determined by GLC, infra-red, mass, and nuclear magnetic spectroscopy of the isolated compounds and several synthetic isomers. Two additional minor components were not identified. The tubular, spirally stiffened gland reservoirs are derived from the seventh intersternal membrane and are homologous to other defensive glands in the subfamily Tenebrioninae. Upon handling, the secretion is released by protracting the sixth and seventh sternites and everting the proximal quarter of the reservoir. With its legs, the beetle wipes the secretion onto itself and the handler. The well-tracheated secretory tissue consists of strands and sheets of cells arranged along and attached by their long effluent ducts which empty along a transverse line near the reservoirs' posterior opening. The surface of the reservoir sacs is covered with a thin epidermis. Electron microscopy of the gland tissue revealed a secretory unit which consists of a long tubular cuticle-lined organelle sequentially ensheathed by three types of cells: (1) a cell with a large microvillusfilled vesicle surrounding the blind distal end of the cuticular organelle, (2) an adjacent second cell into whose central vesicle (which is delimited by small sparse microvilli) the cuticular organelle passes, becoming expanded and diverticulated, and (3) at least one tubule-sheathing cell surrounding each separate cuticular organelle from the point at which it leaves the second cell to its proximal termination at the reservoir.

Insect Defensive Secretions: Hex-2-enal-1 in Pelmalosilpha coriacea (Blattaria) and Its Repellent Value under Natural Conditions1

Adults of the brachypterous blattid Pelmatosilpha coriacea Rehn eject hex-2-enal-1 when they are disturbed. This compound is stored in a large sac situated between the sixth and seventh sternites. Under field conditions, the secretion of Pelmatosilpha was observed to be an effective repellent of ants. On the other hand, this cockroach was eaten readily by lizards of the genus Anolis. The implications of these results are discussed.

The Sternal Scent Gland of Eurycotis Floridana (Blattaria: Blattidae)

The cockroach Eurycotis floridana (Walker) secretes 2-hexenal in a large median ventral gland in the abdomen (Roth et al., 1956). The gland is a lobed sac formed by an invagination of the epidermis between the sixth and seventh abdominal sternites. Two distinctly separated lobes of the gland arise on each side of the ventral nerve cord and extend forward to the third sternite (fig. 1). The large lobes consist of two or three less distinct lobes. When the gland is distended with fluid, its surface is smooth and the lobes are distinct. Tracheae, branching from the median ventral tracheal trunks, ramify extensively over the surface of the gland. Fat body is closely associated with the scent gland by means of tracheal attachments. Inconspicuous longitudinal muscles arise along the ventral surface of the two main lobes and insert near the median line at the anterior edge of the sixth sternite. No detectable nerves are connected with the gland. The gland opens to the exterior between the sixth and seventh sternites. A U-shaped indentation in the middle of the anterior margin of the seventh sternite delimits the dorsal side of the opening; the ventral side of the opening is slightly wider (fig. 2). Just posterior to the aperture of the gland is a crescent-shaped, rigid thickening in the intersegmental membrane (fig. 2,R). As there is no sphincter muscle at the opening of the gland and no muscles in the wall of the sac, the discharge of fluid from the gland seems to be controlled by the longitudinal muscles which attach the gland to the sixth sternite. Contraction of these muscles would elongate the sac and thereby decrease its volume and force the fluid out through the narrow slit of the closely opposed sternites (fig. 3). Similarly, general contraction of the abdomen would compress the fluid-filled sac and force out the liquid. The fluid can be ejected for a considerable distance (Roth et al, 1956).

Canadian Species ofLatalus(Homoptera: Cicadellidae)

Three North American species ofLatalusand four ofQuontuswere listed by Oman (1999). Two of these are conspecific with a third and three new species are described below. Two of the previously described species have not been found in Canada and are not discussed here. They areDeltocephalus latidensSanders and DeLong (1919, p. 234) andLatalus uncinatusBeamer and Tuthill (1934, p. 6). They are distinguished by genitalic characters described in the original descriptions.QuontusOman (1949) is treated here as a synonym ofLatalusDeLong and Sleesman (1929), as the distinctions given by Oman (1949) intergrade and do not always hold good. Canadian species ofLatalusapparently inhabit grasslands. The best specific characters are in the internal male genitalia, though the female seventh sternite shows valid characters in some species.

Canadian Species of Orocastus and Auridius (Homoptera: Cicadellidae)

Leafhoppers of the genera Orocastus and Auridius are locally abundant in grassland regions in Western Canada. They are small insects, the males golden yellow and the females stramineous in colour. The two genera are distinguished from each other by characters of the internal male genitalia. The species are distinguished primarily by these characters and by the form of the seventh sternite of the female. There has been some confusion between the species, partly because the sexes were wrongly associated by some authors and partly because the extent of the individual variation was not appreciated fully. The following are descriptions and illustrations of the distinctive character; of the four species found in Canada, with notes on the distributions and variation. One species new to science is described and one species is reduced to synonymy.