Metathoracic Spiracle Research Articles

External structures of the metathoracic scent gland efferent system in the true bug superfamily Pyrrhocoroidea (Hemiptera: Heteroptera: Pentatomomorpha)

Pyrrhocoroidea represents an important group of true bugs (Insecta: Hemiptera: Heteroptera) which includes fire bugs, cotton stainers and other taxa widely used in experimental studies or known as pests. However, the morphology and phylogeny of Pyrrhocoroidea have been only poorly studied so far. Here, structures of the external scent efferent system of the metathoracic scent glands are examined in 64 out of 71 currently valid genera of Pyrrhocoroidea and scanning electron micrographs are provided for most taxa. Several characters are revealed which define each of the three higher taxa within Pyrrhocoroidea: Larginae (small auriculate peritreme lacking manubrium and median furrow; metathoracic spiracle never surrounded by evaporatorium), Physopeltinae (large, widely open ostiole; large peritremal disc with manubrium [new term], lacking median furrow; mace-like mycoid filter processes of equal shape and size on both anterior and posterior margins of metathoracic spiracle), and Pyrrhocoridae (elongate auriculate peritreme with deep median furrow). Within Pyrrhocoridae, three main types (A, B and C) of the external scent efferent system are distinguished, differring in the amount of reductions. The findings are interpreted in the context of phylogenetic hypotheses available for Pyrrhocoroidea and their close relatives, Coreoidea and Lygaeoidea. An updated identification key to the families and subfamilies of Pyrrhocoroidea applicable for both sexes is provided.

Morphological diversity of the metathoracic spiracle in the Lygaeoidea (Hemiptera: Heteroptera)

Spiracles are the openings in the exoskeleton of insects through which air enters into the respiratory system that is formed by a series of tubes called tracheae. They are primarily located on the abdomen, but can also occur on the thorax, including the metathorax. An insect metathoracic spiracle is usually composed of an external opening and a more internal filter apparatus. We propose new terminology for these structures, and we explore the value in their use in taxonomic and phylogenetic studies within the true bug infraorder Pentatomomorpha, with emphasis on the superfamily Lygaeoidea (Insecta: Hemiptera: Heteroptera). These structures were studied using scanning electron microscopy. Two types of metathoracic spiracle external openings were recognized: a narrow opening (type N), which is slit-like; and a wide opening (type W), with internal fine structures located between the mesothoracic and metathoracic margins of the interpleural suture clearly visible. The filter apparatus in the Pentatomomorpha consists of modified mushroom bodies of the metathoracic scent gland evaporatorium, for which the term mycoid filter processes is proposed. Eight different types of mycoid filter processes, and an unmodified microsculpture type (a type with usual cuticular microsculpture) and filter setae can be found on the anterior or posterior margins of the metathoracic spiracle. We believe the wide opening (type W) to be the plesiomorphic character state in the Pentatomomorpha, with multiple, independent transformations leading to the narrow opening in Lygaeoidea. Considerable variability in the structure of the spiracle opening (in Lygaeoidea), and in the structure of the mycoid filter processes (in Pentatomomorpha) was detected. Overall, we found the morphology of these structures to be of limited value concerning the taxonomy or for determining phylogenetic relationships of the higher taxa (families) of Pentatomomorpha, but they may be useful as additional evidence for taxonomic and phylogenetic studies at the generic and perhaps the tribal levels.

X-ray computed tomography study of the flight-adapted tracheal system in the blowflyCalliphora vicinaanalysing the ventilation mechanism and flow-directing valves

Following the discovery of flight motor-driven unidirectional gas exchange with rising PO2 in the blowfly, X-ray computed tomography (CT) was used to visualize the organization of the tracheal system in the anterior body with emphasis on the arrangement of the pathways for airflow. The fly's head is preferentially supplied by cephalic tracheae originating from the ventral orifice of the mesothoracic spiracle (Sp1). The respiratory airflow during flight is a by-product of cyclic deformations of the thoracic box by the flight muscles. The air sacs below the tergal integument (scutum and scutellum) facilitate the respiratory airflow: the shortening of the thorax turns the scutellum and the wings downward and the scutum upward with a volume increase in the scutal air sacs. The resulting negative pressure sucks air from Sp1 through special tracheae towards the scutal air sacs. The airflow is directed by two valves that open alternately: (1) the hinged filter flaps of the metathoracic spiracles (Sp2) are passively pushed open during the upstroke by the increased tracheal pressure, thereby enabling expiration; (2) a newly described tracheal valve-like septum behind the regular spiracular valve lids of Sp1 opens passively and air is sucked in through Sp1 during the downstroke and prevents expiration by closing during the upstroke. This stabilizes the unidirectional airflow. The tracheal volume of the head, thorax and abdomen and their mass were determined. Despite the different anatomy of birds and flies, the unidirectional airflow reveals a comparable efficiency of the temporal throughput in flies and hummingbirds.

Structure of the thoracic spiracular valves and their contribution to the unidirectional gas exchange in flying blowfliesCalliphora vicina

The operation of the thoracic spiracular valves was analysed using anatomical and physiological techniques. Dense spiracular filter trichomes impede a diffusive gas exchange. However, the hinged posterior filter flap of the metathoracic spiracle (Sp2) opens passively during upstroke of the wings and closes by the suction of the sub-atmospheric tracheal pressure during the downstroke, which supports a unidirectional respiratory airflow. The action of the interior spiracular valve lids was recorded by photocell sensors oriented above the enlarged spiracles and projected onto the screen of a video camera. The thoracic spiracles opened much quicker (approximately 0.1 s) than they closed (1 s), suggesting that the spiracular muscles are openers, as confirmed by experimental induction of muscle contraction. Simultaneous photocell measurement revealed that the first and second thoracic spiracles act concordantly. At rest, the spiracles were mostly closed or only slightly open (<1%). During intermittent short flights, the valves opened wide at the start of the flight for a short time, and in many cases opened again after the flight ended. Often, the opening was wider after the flight ended than during the flight itself. During long spontaneous continuous flight phases (up to 2h), the valves were only slightly open (<5%), widening shortly after transient increases of wing stroke intensity. It is an amazing paradox that the spiracles were only slightly open when the requirement for O2 was high during sustained flight. The advantage of generating sub-atmospheric pressure, supporting a unidirectional airflow with a PO2 increase above the resting level, is discussed.

Comparative thorax morphology of death-feigning flightless cryptorhynchine weevils (Coleoptera: Curculionidae) based on 3D reconstructions

The thorax morphology, especially the muscles and the tracheal system of three flightless species of Cryptorhynchinae is examined by digital 3D reconstructions based on synchrotron X-ray microtomography and compared to other Curculionidae. Wings, metanepisternites, and muscles functional in flight are fully reduced in the species examined: Kyklioacalles roboris (Curtis), Trigonopterus scharfi Riedel and Trigonopterus vandekampi Riedel. All three share the same set of thoracic muscles, but differences exist in the shape and size of muscles. Both Trigonopterus species examined have a conspicuous fan-shaped branch of Musculus mesosterni primus contracting pro- and mesothorax, interpreted as an adaption to their thanatosis defense strategy. Trigonopterus vandekampi furthermore shows a marked increase in the size of two metacoxal muscles, which may be functional in this species' thanatosis blocking mechanisms. The metathoracic spiracle of all Trigonopterus species is located at the side of the metaventrite externally and not in the subelytral space as in other beetles. It is hypothesized that this translocation was triggered by the need to improve oxygen supply during thanatosis, when both the mesothoracic spiracle and the subelytral cavity are tightly sealed from the outside.

Flight-motor-driven respiratory airflow increases tracheal oxygen to nearly atmospheric level in blowflies (Calliphora vicina).

It is widely accepted that an efficient oxygen supply and removal of CO2 in small flying insects are sufficiently performed by diffusion with open spiracles. This paper shows that in the tethered flying blowfly, gas exchange occurs by autoventilation and unidirectional airflow. The air is inspired through the mesothoracic spiracles (Sp1) during the downstroke of the wings and is expired through the metathoracic spiracles (Sp2) during the upstroke. This directed airflow through the thoracic tracheal system was documented by pre-atrial pressure measurements at the Sp1 and Sp2, revealing a sub-atmospheric mean pressure at the Sp1 and an over-atmospheric mean pressure at the Sp2. In the mesothoracic air sacs, the mean pressure is sub-atmospheric, conditioned by the only slightly open spiracles. In a split flow-through chamber experiment, the CO2 released through the Sp2 confirmed this unidirectional respiratory gas flow, implicating an inner tracheal valve. In the thoracic tracheal system, the PO2 during flight exceeds the high resting PO2 by 1-2 kPa, reaching nearly atmospheric values. In the abdominal large air sacs, the PO2 drops during flight, probably due to the accumulation of CO2. Periodic heartbeat reversals continue during flight, with a higher period frequency than at rest, supporting the transport of CO2 via the haemolymph towards the metathoracic tracheae and abdominal air sacs.

Spiracular Structure Differs Among Adult and Larval Phlaeothripids (Thysanoptera: Phlaeothripidae) Recorded in California Deserts

Spiracles on Thysanoptera have a diverse and complex structure suggesting they function as plastrons and enable respiration during submergence from rainfall or flooding. I examined the mesothoracic, metathoracic, and first-abdominal spiracles on adult males and females of 4 species of Phlaeothripidae that inhabit the Mojave and Sonoran Deserts. Spiracles contained open pores surrounded by a network of cuticle. I observed 2 classes of spiracle structure, termed compound and simple. Most pores on compound spiracles contained a central spot of cuticle. Most pores on simple spiracles lacked a cuticular spot. Compound spiracles were observed on Leptothrips larreae Hood. Simple spiracles were observed on Liothrips xanthocerus Hood, Leptothrips fasciculatus (Crawford), and the wing-dimorphic Bagnalliella mojave Hood. First- and second-instar larvae of L. larreae and L. fasciculatus supported the same class of spiracles as adults. Metathoracic spiracles on macropterous B. mojave females were slightly larger than those on brachypterous females. A live L. larreae adult submerged in water, and illuminated obliquely from above, reflected light from its pterothoracic spiracles, indicating that they trap air and likely function as plastrons. Pterothoracic spiracles were also examined on museum slides of adult females of 8 additional, phlaeothripid species recorded in California at desert localities or on desert plants. Four species have compound spiracles, and 4 species have simple spiracles. These 2 classes of spiracles were independent of body size. Spiracle class was weakly, and non-significantly, dependent on brachyptery in either sex. All 4 species with brachypterous males or females produce adult females with simple spiracles. Of the 8 species with only macropters, 5 species support compound spiracles, and 3 species support simple spiracles. Simple spiracles may be more common on desert Phlaeothripidae that produce brachypters and live in enclosed microhabitats, providing more protection from submergence in rainfall.

Fine structure of Delia platura (Meigen) (Diptera: Anthomyiidae) revealed by scanning electron microscopy.

Delia platura (Meigen) is a phytophagous fly that can cause significant crop losses. To obtain a better understanding of the external morphology of this species, adult D. platura is studied using scanning electron microscopy. Organs or structures that are important for taxonomy, such as the compound eyes, spiracles, pulvilli, wings, and genitalia are highlighted to complement previous description based on light microscope. Mesothoracic and metathoracic spiracles of D. platura that provide efficiency in preventing entrance of fine materials or dust into the tracheal system are morphologically different. In addition, the elongate-oval pulvillus is densely covered with tenent setae with spoon-like tip, which can increase the number of contact points for attachment to a surface. Four types of sensilla are observed on the male genitalia of D. platura including: trichoid sensilla, chaetic sensilla, three subtypes of campaniform sensilla, and basiconic sensilla. Long bristles and microtrichiae are observed on the female genitalia of D. platura. The possible function of sensilla located in the genitalia of D. platura is discussed. Microsc. Res. Tech. 77:619-630, 2014. © 2014 Wiley Periodicals, Inc.

Review of the genus Namadytes Hesse, 1969 (Insecta: Diptera: Mydidae: Syllegomydinae).

The Mydidae genus Namadytes Hesse, 1969 is reviewed. It is known from five species, primarily occurring in Namibia. The study of newly available material from both Namibia and South Africa deposited in several natural history collections results in the recognition of three species and new synonymy of two, i.e., Namadytes pallidus Hesse, 1972 is a new junior synonym of Namadytes maculiventris (Hesse, 1969) and Namadytes prozeskyi Hesse, 1969: 282 is a new junior synonym of Namadytes vansoni Hesse, 1969: 280. All three species are re-described and comments on sexual dimorphism and intraspecific variation are made, a dichotomous key for their identification is presented, and illustrations and photographs are provided to support the descriptions and facilitate future identification. Distribution, occurrence in biodiversity hotspots sensu Conservation International, and seasonal incidence with associated weather and climatic data are discussed for all species. A morphological structure ventral to the halter and posterior to the metathoracic spiracle, the infra-halter sclerite, is here newly termed.

Brachymyrmex species with tumuliform metathoracic spiracles: description of three new species and discussion of dimorphism in the genus (Hymenoptera, Formicidae)

Brachymyrmex is a taxonomically challenging ant genus that is badly in need of review. Most species are very small and soft bodied and current descriptions regularly lack clarity making species identification a daunting task. Furthermore, the monophyly of Brachymyrmex has not been established and the relationships among its species and with closely related genera are poorly understood. Most species of Brachymyrmex are monomorphic, but two dimorphic species have been assigned to the genus before. Here, we redescribe these dimorphic taxa, B. pilipes and B. micromegas, and describe three new monomorphic species, B. brasiliensis sp. n., B. delabiei sp. n. and B. feitosai sp. n. All five species occur in Brazil and have tumuliform metathoracic spiracles, which are lacking in other Brachymyrmex species. We discuss dimorphism and its evolution in the genus and provide a distribution map, illustrations and a species identification key based on workers.

Thoracic scent efferent system of the Tessaratomidae sensu lato (Hemiptera: Heteroptera: Pentatomoidea) with implication to the phylogeny of the family

We studied the cuticular structures associated with the opening of the adult metathoracic scent glands in the family Tessaratomidae. The terminology previously used for these structures in the Tessaratomidae and Pentatomoidea is briefly reviewed and most suitable terms are selected (i.e., metathoracic scent apparatus, internal and external scent efferent system, internal orifice, vestibule, ostiole, ostiolar groove, peritreme, auricle, spout, groove, ruga, disc, peritremal lobes, evaporatorium, mycoid surface, mushroom body, bridge, alveole, trabeculae, and peritremal surface). We examined and illustrated external scent efferent system of 40 species from 33 genera belonging to all three subfamilies of Tessaratomidae sensu lato, i.e. Tessaratominae, Natalicolinae, and Oncomerinae. Three basic types were recognized: i) Oncomerinae – ostiole slightly removed laterally from the position between coxal acetabula, oval, ostiolar groove not developed or very short, peritreme in form of spout attached anterolaterally to the ostiole; ii) Tessaratomidae sensu stricto (= Tessaratominae + Natalicolinae) – ostiole situated between acetabula, strongly incised mesad, thus vestibule distally opened in two planes (ventrally and laterally) as ostiolar groove, peritreme in form of anterior and posterior peritremal lobes surrounding the ostiolar groove; and iii) Platytatina (Platytatus ambiguus Bergroth, 1892) – ostiole shifted near to lateral metapleural margin, ostiolar groove reduced, situated between two flat, reniform processes (median and lateral lobe). A polarity of these structures is suggested: the type i) of Oncomerinae is regarded as plesiomorphic(shared with Urostylididae, Dinidoridae, etc.); the type iii) of Platytatina is homologized with type ii) of Tessaratominae sensu stricto; the type ii) is unique within Pentatomoidea and considered as an autapomorphy. The information content of the characters of the external scent efferent system and metathoracic spiracle for a phylogenetic hypothesis of relationships within Pentatomoidea is tested by cladistic analyses. We found some apomorphies helping to define Tessaratomidae and Plataspidae, most of the characters, however, seem to be homoplasious at family level. The results of the cladistic analyses further support the monophyly of Dinidoridae + Tessaratomidae sensu lato and that of Tessaratomidae sensu stricto, while the relationships of Oncomerinae and Tessaratomidae sensu stricto as well as the relationships among the family-group taxa within Tessaratomidae sensu stricto need further studies.

Ultrastructure of spiracles of Musca domestica and Hydrotaea chalcogaster (Diptera: Muscidae)

Spiracles are major respiratory openings in the exoskeleton of insects. Oxygen, a necessary gas for cell activity, must pass through the spiracle to enter the respiratory system. In this study, we investigated the fine structure of spiracles of adult females of Musca domestica L. and Hydrotaea chalcogaster (Wiedemann), both medically important fly species in many parts of the world, by utilizing scanning electron microscopy. The mesothoracic spiracle of M. domestica is large and elongate-oval in shape, with its anterior end being gradually tapered. The outer surface is densely covered with slender setae of variable distribution and orientation. The metathoracic spiracle is semicircular or D-shaped, with its rim possessing long, fine, inwardly curved setae. A net-like valve or sieve plate, which has a smooth rim with swollen surface, is located within the atrium of this species. The abdominal spiracles are circular with a symmetrically swollen peritreme surrounding the opening. The inner filtering apparatus is composed of many spiral tubes, each possessing many small spines. As for H. chalcogaster, the tapering mesothoracic spiracle is covered with long setae arranged consistently inward from the peritreme, giving it a "combed" appearance. The metathoracic spiracle is similarly arranged but triangularly rounded in shape, with the anterior and posterior rims possessing long fine setae. The net-like valve within the atrium has a smooth, swollen rim, whereas the inner edge of the atrium bears short, slender setae where it meets with the peritreme of the spiracle. The abdominal spiracles of this species look similar to that of M. domestica, with the exception of the filtering apparatus that bears only a few small spines. The function of these spiracles is discussed.

The role of the subelytral cavity in water loss in the flightless dung beetle, Circellium bacchus (Coleoptera: Scarabaeinae)

Circellium bacchus is a flightless telecoprid (ball-rolling) dung beetle, endemic to the afrotropical region, where it is found in a few restricted populations in the eastern Cape of South Africa. Its apterous condition and large size (mass ranges from 6 to 12 g) are considered to be adaptations to a semi-arid habitat. This beetle is active in the sun for long periods, walking between widely scattered dung pats, thus is under selection pressure to reduce water loss.C. bacchus has eight spiracles on each side of the body. The metathoracic spiracle and six abdominal spiracles open into the subelytral cavity, which is closed. The mesothoracic spiracle is the largest and most exposed, occurring ventrally in the membrane connecting the prothorax and mesothorax.When at rest a cyclic form of respiration, known as discontinuous gas exchange cycle, is used by C. bacchus, releasing a burst of carbon dioxide approximately once an hour when the spiracles open for about 33 minutes. Flow-through respirometry was used to measure water loss from the thorax (being the head, prothorax and mesothorax) and elytral case (containing the metathorax and abdomen) separately. The total water loss of C. bacchus could be divided up as 65% cuticular water loss from the thorax, 35% cuticular water loss from the elytral case, 4% respiratory water loss from the thorax and no measurable respiratory water loss from the elytral case. 1.51 &micro;g of water is lost for every &micro;l of CO2 emitted during respiration in the thorax. Thus, the main avenue for both respiration and respiratory water loss is via the mesothoracic spiracles, suggesting that the primary function of the subelytral cavity is not to reduce respiratory water loss.

Flight-motor-driven respiratory air flow in the hawkmoth Manduca sexta.

Intratracheal pressure during tethered flight was analyzed at the anterior spiracles and mesoscutellar air sacs in the hawkmoth Manduca sexta using electronic pressure sensors. CO(2) emission from the anterior spiracles and the posterior thoracic and abdominal spiracles was measured using a URAS gas analyzer with a split-specimen chamber. Experiments were accompanied by photocell recordings of the wingbeat. The structural differences between the mesothoracic and metathoracic spiracles are described. Deformations of the lateral thorax and their effect upon the spiracles were observed under stroboscopic light. During shivering, ventilation pulses are generated by the flight muscles reminiscent of an autoventilation mechanism with tidal air flow. During steady flight, however, a unidirectional airstream arises with a mean negative (subatmospheric) pressure at the first (mesothoracic) spiracles and a mean positive pressure in the mesoscutellar air sacs. As a result of this pressure difference during flight, CO(2) is emitted only at the posterior spiracles. The suction force for the inspiration flow at the anterior spiracles is generated by the flight apparatus as a result of prevention of inspiration through the posterior thoracic spiracles. During the downstroke, the volume of the thoracic air sacs increases, while the posterior thoracic spiracles are automatically enclosed in the subalar cleft below the wing hinge and are probably closed. During the upstroke, the air sac volume decreases and the moth expires through the open posterior spiracles.

Directionality of the tympanal vibrations in a cicada: a biophysical analysis

1. Laser vibrometry and acoustic measurements were used to study the biophysics of directional hearing in males and females of a cicada, in which most of the male tympanum is covered by thick, water filled tissue “pads”. 2. In females, the tympanal vibrations are very dependent on the direction of sound incidence in the entire frequency range 1–20 kHz, and especially at the main frequencies of the calling song (3–7 kHz). At frequencies up to 10 kHz, the directionality disappears if the contralateral tympanum, metathoracic spiracle, and folded membrane are blocked with Vaseline. This suggests some pressure-difference receiver properties in the ear. 3. In males, the tympanal vibrations depend on the direction of sound incidence only within narrow frequency bands (around 1.8 kHz and at 6–7 kHz). At frequencies above 10–12 kHz, the directionality appears to be determined by diffraction, and the ear seems to work as a pressure receiver. The peak in directionality at 6–7 kHz disappears when the contralateral timbal, but not the tympanum, is covered. Covering the thin ventral abdominal wall causes the peak around 1.8 kHz to disappear. 4. Most observed tympanal directionalities, except around 1.8 kHz in males, are well predicted from measured transmissions of sound through the body and measured values of sound amplitude and phase at the ears at various directions of sound incidence.

Defensive Secretion Production in Lubber Grasshoppers (Orthoptera: Romaleidae): Influence of Age, Sex, Diet, and Discharge Frequency

The lubber grasshoppers Romalea guttata (Houttuyn) and Taeniopoda eques (Burmeister) discharge a defensive secretion from paired metathoracic spiracles. The amount of stored secretion varies greatly among individuals and is influenced by age, stage, sex, diet, species, body weight, and prior discharge. Later instars possess more secretion than younger instars and females possess more than males. When lubbers molt, all stored secretion is lost; thus freshly molted insects lack exudate. Newly molted adult lubbers increased the amount of stored secretion at an age-related variable rate that peaked on day 4 in T. eques and day 7 in R. guttata. Thereafter, secretion production continued, but at reduced rates. In adults of both species, secretion volume was positively correlated with body weight. In T. eques, discharge of secretion from the spiracles does not influence the rate of filling of the gland reservoir. In R. guttata, a polyphagous diet or a monophagous diet of onion leaves, Allium sp., produced significantly more secretion than diets of wild cucumber, Melothria pendula L., or grapefruit, Citrus paradisi Macfady. leaves. Wild R. guttata adults have more secretion than wild T. eques adults, possibly because of the latter's adaptation to a dry desert environment. This study suggests that numerous factors influence secretion volume and hence defensive efHcacy in lubber grasshoppers. Lubber predators are thus confronted with a variably defended prey, whose defensive capabilities increase over time and with certain diets.

Anatomy, ultrastructure, and functional morphology of the metathoracic tracheal defensive glands of the grasshopper Romalea guttata

In the lubber grasshopper Romalea guttata, the respiratory system produces, stores, and delivers a phenolic defensive secretion. The exudate is secreted by a glandular epithelium surrounding the metathoracic spiracular tracheal trunks. Embedded in the glandular tissue are multiple secretory units, each comprised of a basal secretory cell and an apical duct cell. Secretory cells have numerous mitochondria, a tubular, smooth endoplasmic reticulum, well-developed Golgi bodies, and a microvillilined vesicle thought to transfer secretion to the intracellular cuticular duct of a duct cell. Ducts empty into the metathoracic tracheal lumina where the exudate is stored behind the closed metathoracic spiracle. Tactile stimulation elicits secretion discharge, which begins when all spiracles except the metathoracic pair are closed and the abdomen is compressed. Increased hemostatic and pneumatic pressures drive air and secretion out of the spiracle with an audible hiss. Both metathoracic spiracles discharge simultaneously. The secretion erupts first as a dispersant spray, then as an adherent froth, and finally assumes the form of a slowly evaporating repellent droplet. Discharge force and number vary with eliciting stimuli, volume of stored secretion, and age, disturbance state, and temperature of the insect. Molting grasshoppers are unable to discharge because the stored exudate is lost with the shed cuticle. The advantages and limitations of a tracheal defensive system are discussed.

Adaptations to Endoparasitism in the Larval Integument and Respiratory System of the Flea Uropsylla-Tasmanica Rothschild (Siphonaptera, Pygiopsyllidae)

An histological study of flea larvae was carried out in order to compare free-living larvae with the unique endoparasitic larva of Uropsylla tasmanica, a species found on marsupial cats in Tasmania and Victoria, Australia. The free-living species examined were the cat flea Ctenocephalides felis, and Odontopsyllus quirosi. Body shape in U. tasmanica is adapted to endoparasitism; the anterior segments are greatly expanded and the abdominal segments are reduced from ten to eight. This reduction brings the last abdominal spiracle (8), to the posterior end of the larva, allowing better access to oxygen from the atmosphere. Possible evolutionary steps in this modification are suggested. Third-instar U. tasmanica have non-functional prothoracic spiracles and the metathoracic spiracles are either non-functional or absent. All three instars of C. felis are peripneustic, and third-instar O. quirosi larvae are holopneustic. Contrary to previous ideas, the respiratory systems of flea larvae do not provide exceptions to the generalisations that in holometabolous insect larvae the metathoracic spiracle is nearly always non-functional, and, that functional and non-functional spiracles coexist in these larvae. Features in U. tasmanica convergent with those of endoparasitic, saprophagous and aquatic fly larvae are discussed.

Biology of Taeniopoda eques (Orthoptera: Acrididae) in Southeastern Arizona

Life history parameters are given for Taeniopoda eques (Burmeister) including habitat characterization, distribution, phenology, morphometrics, diet, and natural enemies. Molting, mating, oviposition, dispersal, daily, thermoregulatory, and disturbance behaviors are examined. Hatching and abundance for this desert dweller are closely linked to onset of summer rains and appearance of ephemeral food plants. Times from egg hatch to adult, mating, oviposition, and death are ca. 39, 56, 74, and 105 days, respectively. Five instars are distinguished by pronotum length, head width, and wing pad development. Fresh eggs weigh 0.029 g; 40-day-old adult males, 2.75 g; females, 8.26 g. Molting is primarily diurnal, but extends past sunset on warm nights. Temperature influences molting success; no molting occurred at temperatures below 22°C. The molt to adult requires 86.8 min at 30°C. Both sexes mate repeatedly. Males are sexually aggressive, females passive. During the long copulation (ca. 14.1 h) multiple spermatophores are passed. Females oviposit diurnally 4–8 cm deep in soil under shrubs. T. eques feeds mainly on low-growing desert annuals, but takes dead or incapacitated arthropods, feces, or raindrops. First instars aggregate strongly; later instars weakly. A cyclical daily movement into and out of nonfood shrubs is thought to alleviate predator and thermal pressures. Male movement exceeded that of females. Beauveria bassiana and other microorganisms were found in moribund grasshoppers. T. eques is chemically protected from some predators. Aggregation, aposematism, and noisy expulsion of an odorous secretion from metathoracic spiracles advertise and reinforce chemical defense.

A New Lanthus (Odonata:Gomphidae) from Eastern North America with Adult and Nymphal Keys to American Octogomphines2

A brief taxonomic and nomenclatural history of Lanthus parvulus (Selys) and Stylogomphus albistylus (Hagen) are given, and the adults and nymphs of L. parvulus and L. vernalis n. sp. described. The new species may be readily distinguished from L. parvulus by the confluence of the mesanepimeral and metanepisternal pale stripes above the metathoracic spiracle. The type locality of L. vernalis n. sp. is in western Virginia, and the type series includes specimens from Maine to Georgia. Both species of Lanthus prefer pristine upland streams and are valuable biological indicators. Species keys for the determination of adults and nymphs are given, and the taxonomic position of the genus Lanthus and related genera discussed.