A spontaneous translocation heterozygote involving centromere regions in Gomphocerus sibiricus (L.) (Orthoptera: Acrididae)

A spontaneous interchange with breaks in the centromeric regions of the L₂ and L₃ submetacentric chromosome pairs is described, using the C-banding technique, in a male of the mountain grasshopper Gomphocerus sibiricus (2n=17). In 100% of the examined cells from standard follicles of the mutant, the interchange was present as a ring of four and concordant separations during anaphase-I were always observed. The orientation of these rings is predominantly either adjacent I or II and a very much lower frequency was detected for the alternate type. Fertility is therefore expected to be low. — A single follicle was found where the centromeric region of the 3² chromosome had split, resulting in two telocentric chromosomes. At meiosis chains with five centromeric regions resulted. The nature of the original interchange has been interpreted on the basis of this new aberration. — A large variation in the number of nucleoli is regularly present in spermatocytes at the same stage and differences between the two karyotypes (mutant and standard) could not be demonstrated using Ag-staining. This technique has also been used to study the morphology, with respect to number and localization of the adjunct centrioles, of the spermatids in the mutant.     

On the ordered arrangement of the haploid complement in radial metaphases of secondary meiocytes of male grasshoppers,Euchorthippus pulvinatus gallicus

Summary Five hundred and ninety-three radial metaphase II cells from the male grasshopper, Euchorthippus pulvinatus gallicus, were analyzed to ascertain whether chromosomes in the haploid complement were in a fixed order. As an a posteriori hypothesis, the most probable original order of chromosomes in the metaphases was determined. The genetical significance of a suprachromosomal organization is discussed.     

The B-chromosomes of Neopodismopsis abdominalis (Orthoptera,Acrididae)

As an extension of an earlier study, the behaviour of two kinds of supernumerary chromosomes has been re-examined in populations of Neopodismopsis abdominalis (Acrididae) from Ontario. One of these is minute and metacentric (B^S); the other is large and heterochromatic (B^L). The B^S has a 40% probability of undergoing precocious separation when present as a univalent. This separation may lead to restitution and subsequently to macrospermatid formation. The frequency of macrospermatids was a power function of the number of precocious B^S elements per cell and approached 20% in 4B^S-individuals. Individuals with high numbers of B^S occur in slight excess of Poisson expectation possibly reflecting a mechanism which compensates for the detrimental effects of the B^S. The B^L, by contrast, does not undergo precocious division and neither micro- nor macro-spermatids ascribable to the B^L were seen. Non-disjunction of B-chromosomes occurred very rarely and was seen in only three B^S individuals out of 141 examined and in only two B^L individuals out of 33. Moreover it was equally frequent in caeca and gonad and did not result in a net loss or a net gain of B-chromosomes in the germ line.     

Temporal constancy in grasshopper assemblies (Orthoptera: Acrididae)

ABSTRACT.

• 1 Temporal constancy in the structure of grasshopper assemblies (about forty-five species each) from two types of North American grasslands was assessed; one site was followed 25 years and the other 7 years.
• 2 Densities and relative abundances varied but composition of assemblies based on ranks suggested significant structure when three or more species were included in the analysis.
• 3 Results compared favourably with other insect herbivore assemblies which have been examined; variability in population change was intermediate along the spectrum of organisms which have been studied.

     

Experiments on aggregations of Phymateus purpurascens (Orthoptera, Acrididae, Pyrgomorphinae)

Phymateus purpurascens Karsch has been studied in the wild and in captivity in Uganda. Its habits, colouration, behaviour and life cycle are described.
All individuals are attracted towards each other by visual stimuli, and a moving individual is more attractive than a stationary one. This behaviour is unchanged by several instars in isolation. The aggregated larvae tend to move in synchronous bursts. and it is suggested that this is due to retinal image stabilization by an optomotor reflex.
In an open field all instars are attracted towards isolated vertical objects in the visual field. This, together with the interindividual visual responses described, produces columns of moving insects. No olfactory communication could be demonstrated.
Adults and larvae behave similarly in experimental situations; this contrasts with the observed dispersion in the wild with increasing age. It is suggested that dispersion results from loss of visual contact, caused by (a) loss of the conspicuous larval colouration, (b) chance isolation, and (c) increased mobility of fledged adults. The possible biological function of the gregariou habit is discussed, and the significance of the various colour patterns of the life history as inter-and intraspecific signals.     

Karyotype,heterochromatin content and meiotic features ofPoecilocera picta (Orthoptera,Acrididae)

Cytological study of three distinctly separated populations ofPoecilocera picta revealed a chromosome number of 2N = 18 + XO/ XX. Except for the hemizygosity of a procentric heterochromatic block in the M₆ pair of the Bangalore population, the basic karyotype of the three populations is markedly similar. The autosomal karyotype formula is 2Lt + 4Mt + 1 Mst + 2S st and the telocentric X chromosome is the longest of the complement. All bivalents at pachytene carried procentric heterochromatic blocks. The M₄ is the nucleolus organiser with the NOR region situated interstitially but proximal to the centromere. About 11 μm (4%) of the total (290 μm) autosomal pachytene complement is heterochromatic; a major portion of it is contributed by the S₉ pair which is mostly heterochromatic. Chiasmata are localized proximally and distally and in the S₉ pair their formation is confined to the short procentric euchromatic segment of the long arm. Female meiosis did not reveal any chromomere pattern at pachytene and, unlike in the male, the sex bivalent in the female is indistinguishable from the autosomal bivalents. G- and C-banding patterns in males showed procentric bands in all the chromosomes. In addition there are eight telomeric and two interstitial bands which are C negative. The S₉ pair showed only two bands. The G-banding pattern of the sex chromosome in meiosis showed only a centric band while the heterochromatic body of the facultatively heterochromatic X remained G negative.     

Ronderosia ommexechoides: a new species of Brazilian dichroplini (Orthoptera: Acrididae, Melanoplinae)

A new species of the genus Ronderosia Cigliano 1997 is described. Color illustrations of the female and male, drawings of female and male external genitalia as well as drawings of its phallic structures and photographs of the chromosomes are included.     

Thermoregulation in four species of British grasshoppers (Orthoptera: Acrididae)

1. This study examines the extent to which thermal balance and thermoregulatory ability may contribute to habitat partitioning in insect herbivores.
2. The distribution of four species of grasshopper on a Breckland grass heath is described. Myrmeleotettix maculatus is restricted to short swards, Omocestus viridulus is restricted to long swards, and Chorthippus brunneus and Stenobothrus lineatus are found on swards of intermediate length.
3. Short swards are warmer on average than long swards, but lack cooler refuges on hot days.
4. Chorthippus brunneus and O. viridulus are better able to raise their body temperatures at low ambient temperatures than M. maculatus and S. lineatus . Omocestus viridulus is less able to reduce body temperature at high ambient temperature.
5. Myrmeleotettix maculatus may be precluded from inhabiting cooler long swards because of its inability to raise body temperatures at low ambient temperatures. Omocestus viridulus may avoid short swards because of the danger of overheating.
6. Thermoregulatory ability is a good predictor of the distribution of the grasshoppers in swards of differing length and microclimate.     

The functions of the maxillary palps of Acrididae (Orthoptera)

The functions of the maxillary palps of acridids have been investigated in experiments with Locusta migratoria migratorioides (R. & F.), Schistocerca gregaria (Forsk.) and Chorthippus parallelus (Zett.). The palp makes small irregular flicking movements and more extensive rapid vibrations described as palpation. Both activities involve the same basic movements of the palp segments. Palpation is essentially related to feeding and in normally feeding insects the palps play an important role in food selection, but as starvation is prolonged they become unimportant. Selection depends on appropriate chemical stimulation from the cuticle on the surface of the leaf. Palpation on this leads to head lowering and to biting if appropriate tactile stimuli are then received.The control of biting is discussed. The frequent but very brief, contacts of the sensilla on the tips of the palps with the substratum during palpation may enable them to relay information to the central nervous system more or less continuously without adapting.

---

Zusammenfassung Die Funktionen der Maxillartaster von Locusta migratoria migratorioides (R. & F.), Schistocerca gregaria (Forskål) und Chortippus parallelus (Zett.) wurden unter Anwendung verschiedener Verfahren untersucht. Die Tasterbewegungen wurden kinematographisch analysiert und als Schlagen und Tasten klassifiziert; das letztere tritt hauptsächlich kurz vor und nach, aber ebenso gut auch während der Nahrungsaufnahme auf. Die Sensillen an den Tasterenden berühren beim Tasten häufig das Substrat.Vorausgesetzt, daß die Insekten nicht gehungert hatten, wurde Bellis allein nach Betasten abgelehnt; nach längerem Hungern erfolgte jedoch die Ablehnung erst nach Beißen. Weitere Versuche, bei denen Extrakte der Kutikula von Poa oder Bellis verwendet wurden, zeigten, daß Annahme oder Ablehnung von der chemischen Natur des Substrats abhängen, welches von den Tastern berührt wird. Betasten eines geeigneten Substrats führte nicht unmittelbar zum Beißen, ruft aber eine Verhaltensweise hervor, die ihrerseits das Beißen fördert.Daraus wird geschlossen, daß die von den Tastern wahrgenommenen chemischen Reize für die Nahrungswahl der Acrididen wichtig sind, wenn die Insekten normal fressen. Nach Hunger ruft mechanische Reizung der Taster oder anderer Mundteile Beißen auch beim Fehlen geeigneter chemischer Reize hervor. Die häufigen kurzen Kontakte der Palpen mit dem Substrat während des Tastens erlauben offenbar den Sensillen, einen beständigen Strom von Informationen an das Zentralnervensystem zu liefern, ohne selbst angepaßt (ermüdet) zu werden.

     

Aging and chiasma frequency in Eyprepocnemis plorans (Orthoptera: Acrididae)

The mean frequency of chiasmata was analysed in 29 males of the grasshopper Eyprepocnemis plorans at three different ages considered representative of the whole adult life in this species. In the factors which could potentially affect the parameter studied—namely age, family, individual and the presence or absence of B chromosomes—significant differences were only observed at the individual level. Aging produces no general effect but interacts strongly with the individuals though the age-induced variations in chiasma frequency are not directional. The fact that the range of chiasma frequency variation found within individuals at different ages is comparable to that existing among individuals indicates that the adaptive role of such variations in natural populations must be taken with caution.     

Behavioral influences on food selection in grasshoppers (Orthoptera: Acrididae)

Host plant selectivity has been established for many species of grasshoppers but the mechanisms involved are not completely known. General undirected activity was enhanced by favorable temperature, humidity and illumination. Positive phototactic responses were elicited by directed illumination, color and visual patterns.Orientation to stimuli from food materials generally took place only after contact had been made with the mouthparts. Discrimination among various extracts and extract concentrations from different plant species was demonstrated.Individual grasshoppers in laboratory experiments with artificial diet arrays selected resting sites independent of food location. In some cases feeding was influenced by resting site location.The feeding behavior of grasshoppers will cause them to remain in areas of favorable host plants through a general type of orthokinesis.

---

Zusammenfassung Wirtspflanzen-Wahlvermögen ist bei vielen Feldheuschrecken nachgewiesen worden. Jedoch werden die Eiablage-Orte im allgemeinen nicht mit Rücksicht auf die Verfügbarkeit von Wirtspflanzen für die schlüpfenden Larven gewählt. Diese müssen geeignete Wirtspflanzen unter vielen verfügbaren selbst aussuchen.Innerhalb optimaler Temperatur-und Feuchtigkeitsbereiche wird die allgemeine ungerichtete Aktivität durch genügende Helligkeit verstärkt. Es wurden positive phototaktische Reaktionen zu gerichtetem Licht nachgewiesen. Die Reaktion auf gerichtete Beleuchtung war zwischen 3600 und 4750Å am größten. Wellenlängen ober-und unterhalb davon ergaben geringere Reaktionen.Senkrechte Objekte oder Muster riefen positive Taxien hervor.Olfaktorische Anlockung war sehr begrenzt, aber sobald die Nahrung einmal mit den Mundwerkzeugen in Berührung gekommen war, waren die Heuschrecken sehr wählerisch. Bei verschiedenen Arten wurde die Fähigkeit nachgewiesen, zwischen einer ganzen Reihe von verschiedenen Pflanzenextrakten wählen zu können, die in eine künstliche Trägerdiät eingefügt waren. Unterscheidung zwischen geringen Konzentrationsunterschieden der extrahierten Substanzen war nachweisbar.Zeitraffer-Aufnahmen zeigten, daß die Extraktpräparate in der Reihenfolge ihrer Annehmbarkeit ausgewählt wurden. Gewöhnlich wurde der Fraß auf einige wenige Präparate beschränkt, bis sie völlig verzehrt waren. Erst dann wurden die anderen Präparate in der Reihenfolge ihrer Annehmlichkeit gefressen.Mit Zeitraffer-Aufnahmen wurde das Verhalten einzelner Heuschrecken verfolgt, die zusammen mit Serien von künstlichen Nahrungstabletten mit Pflanzenextrakten gekäfigt worden waren. Es zeigte sich, daß die Heuschrecken Ruheplätze wählen, von denen aus sie sich zum Fressen und Trinken bewegen. Bestimmte Bewegungsmuster waren ausgebildet. Die Lage der Ruheplätze wurde von den anwesenden Nahrungsstoffen nicht beeinflußt, aber in einigen Fällen das Fressen von der Nähe der Ruheplätze.Es wurde angenommen, daß visuelle Reize die Orientierung der Feldheuschrecken unterstützen, aber die Wirtspflanzenwahl findet erst nach Berührung mit den Mundwerkzeugen statt. Feldheuschrecken haben die Gewohnheit, Gebiete, die keine geeigneten Wirtspflanzen enthalten, zu durchqueren und sich auf solchen mit geeigneten Wirten mit Hilfe eines allgemeinen Typs von Orthokinese zu scharen. Da die anziehenderen Pflanzen gewöhnlich auch das größte biologische Potential bieten, werden Verteiling und Dichte der Heuschrecken von der Wirtspflanzenwahl beeinflußt.

---

---

Published with the approval of the Director of the North Dakota Agricultural Experiment Station as journal Article No...... Contribution from North Central Regional Project NC-52.     

On the pronymphal stage in the migratory locust (Locusta migratoria, Orthoptera, Acrididae)

The structure of the integument, somatic and visceral muscles, midgut, and Malpighian tubules were investigated at the late stages of the embryonic and early postembryonic development of the migratory locust, Locusta migratoria, to assess the organization of its pronymphal stage. In its morphogenetic features, the vermiform locust larva sometimes called the pronymph corresponds to the first nymphal instar covered with the second embryonic cuticle which has not been shed. Since the first-instar locust nymphs before and after the shedding of this embryonic cuticle differ significantly in many morphological characters, two consecutive phases of this nymphal instar can be distinguished: the first phase existing from the moment of development of the third embryonic cuticle to the shedding of the second one; the second phase existing from the shedding of the second embryonic cuticle to the formation of the cuticle of the second nymphal instar. Since the pronymphal stage should precede the nymph stage, it may be concluded that the pronymph of the locust is fully embryonized and covered with the second embryonic cuticle, which is also typical of other insects with hemimetabolous development (Konopová and Zrzavý, 2005). Therefore, it would be erroneous to refer to the vermiform first-instar nymph as the pronymph, because the two stages are separated by molting and formation of a new cuticle.     

Food plants of the Moroccan locust Dociostaurus maroccanus (Thunberg, 1815) (Orthoptera,Acrididae) in Turkmenistan

Trophic relationships of the Moroccan locust Dociostaurus maroccanus (Thunberg, 1815) (Orthoptera, Acrididae) hoppers and adults in Turkmenistan are discussed. It was established that food preferences of the locust may vary according to the climatic conditions. Nine species of wild and cultivated plants are recorded as hosts for the Moroccan locust for the first time.     

Female preferences for large, heavy mates inSchistocerca americana (Orthoptera: Acrididae)

The significance of female choice in shaping mating systems remains problematic. The following study clearly documents female preferences in a species of grasshopper,Schistocerca americana, over the course of 3 years. Three sets of animals were observed in an outdoor seminatural cage. Females were found to mate more often with large, heavy males. Furthermore, remating by a female within a week was less likely if she mated with a large or heavy male. Because females were found to oviposit 2 days after a mating on average, these large heavy males may also be chosen cryptically (as defined in the literature) and father more offspring.     

Vitellogenesis in Austracris guttulosa (Walker) (Orthoptera: Acrididae) in Tropical Australia

In tropical northern Australia, vitellogenesis in Austracris guttulosa only occurs if two requirements are met: daylength exceeds 13 h and vegetation is green. During the dry season (April-September), daylength is short and vitellogenesis is inhibited regardless of vegetation condition. Daylength exeeds 13 h by mid October, and vitellogenesis begins by late October if there is green vegetation produced by recent rain. But it is often dry during October and vitellogenesis is delayed until it rains either in November or even December.