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Although most pest grasshopper species in North America overwinter as eggs and hatch in late spring or early summer, some species hatch in late summer, overwinter as nymphs, and become adults in late spring. It is not well understood how nymph-overwintering species impact densities of later-developing pest grasshopper species. In an earlier study examining temporally separated competition, nymphal survival of an egg-overwintering species Ageneotettix deorum, was reduced when high densities of adult nymph-overwintering grasshoppers strongly reduced grass biomass. However, in nature, early instar A. deorum nymphs overlap in time with declining densities of nymph-overwintering grasshoppers, and thus may experience direct competition from them. A field experiment was conducted to examine competitive effects from nymph-overwintering grasshoppers on the survival of A. deorum when phenologies overlapped. Precipitation and grass production during the experiment were well above the long term average. Although the maximum density of nymph-overwintering and egg-overwintering grasshoppers was 100 per m2, interspecific exploitative competition was weak. This study suggests that in years with above-average precipitation, competition between nymph-overwintering adult grasshoppers and later-developing nymphal grasshoppers is likely to be weak, even when densities are high.
This paper summarizes eight years of field study on the Red Locust, Nomadacris septemfasciata (Serville) in southwestern Madagascar and presents management recommendations for its control. This crop pest exhibits a fairly uniform annual life-cycle phenology in southern Madagascar, which involves seasonal migration and adult reproductive diapause. There is one generation/y. Eggs are laid at the beginning of the rainy season in November and December. Eggs hatch in 24–36 d, and the hatchlings reach adulthood in 50–70 d. Fledgling adults enter a reproductive diapause in March and April, and then migrate north and northeast to higher elevations (refuge area where rainfall is > 80 cm/y) where they remain throughout the dry season (May–October). In November (the beginning of the rainy season), the adults migrate south and west to lower elevations (breeding area where rainfall averages 40–80 cm/y) where they mate and initiate oocyte development. Females possess ∼ 162 ovarioles, and typically lay two or three egg pods, each containing ∼ 100 eggs. The six-month adult reproductive diapause is controlled by photoperiod. Eggs and nymphs can experience high mortality, and hence, these stages are key to predicting population dynamics. Based on our findings, we recommend concentrating surveys in the main breeding areas (including one small southwestern fringe with the strongest probability of gregarisation and outbreak), better monitoring of local rainfall abundance and distribution, and better monitoring of deforestation, which increases locust habitat.
The eggs of several Phasmatodea (stick insects) species bear strong resemblances to plant seeds. Such mimicry could increase predation on the eggs by vertebrate granivores, especially on eggs that are not buried by ants. In contrast, predation could be beneficial to the insects if the eggs can survive the digestive tract and hatch afterwards. This experiment tests the hypothesis that granivorous birds can act as dispersal agents for phasmid eggs. The eggs of three walking stick species—Extatosoma tiaratum, Ramulus nematodes, and R. artemis—were offered to two species of terrestrial, granivorous bird: quail (Coturnix japonica) and chickens (Gallus gallus domestica). The birds consumed the eggs eagerly. Examination of the resulting manure showed that most eggs were completely digested. Only one unbroken egg was recovered out of nearly one thousand eggs fed, suggesting that these bird species could not disperse phasmid eggs. Seed-mimicry's fitness costs must be mitigated in nature to explain its prevalence in the Phasmatodea.
Many of the most primitive neotropical bush katydids (Phaneropterinae) — including species of Cosmophyllum Blanchard, Stenophylla Brunner von Wattenwyl, Marenestha Brunner von Wattenwyl, Anisophya Karabag, Coryphoda Brunner von Wattenwyl and Burgilis Stål — are endemic to Chile. The Chilean species, Isophya schoenemanni Karsch, is herein re-affirmed to belong to the genus Anisophya. Two new species of Anisophya from Chile are also described. One is dimorphic in wing length. In 1986 APHIS/PPQ intercepted this species in a shipment of apples from Chile, but it is not likely to be a pest of apples or other pome fruits.
We propose that subfamilies Acridinae (including Truxalinae), Gomphocerinae and Oedipodinae are not monophyletic, and that, as a collective, originated in Africa some time before 100 mya.
Our conclusions are based on a phylogenetic analysis of portions of 5 mitochondrial genes, totalling up to about 2.7 kilobase pairs, in 117 species collected in the Americas, Eurasia, Africa and Australia. Sequences were analyzed by weighted and unweighted maximum parsimony, maximum likelihood and Bayesian methods. Pyrgomorpha conica served as the outgroup. Biogeographic origins and patterns were inferred by applying the programs “DIVA” and “r8s”, for spatial and temporal analyses, respectively.
Maximum sorting of taxa using parsimony was achieved by assigning differential weights to the three codon positions. Resolution was, however, generally poor. Bayesian methods, by contrast, yielded a topology which was virtually identical to the maximum likelihood tree and, for the most part, fully resolved and interpretable. We provide arguments in support of favoring the use of the Bayesian tree to infer relationships and biogeographic origins.
Neither subfamily, as defined in the current on-line Orthoptera Species File 2, proved to be monophyletic. Instead, taxa assorted themselves into 3 broad categories: 1) Gomphocerinae, plus a small subset of acridines; 2) a sister group consisting of Oedipodinae, plus another small subset of acridines; and basal and paraphyletic to this pair, 3) the remaining taxa, all African and primarily members of the Acridinae. Very few tribes within these subfamilies proved to be monophyletic.
This phylogenetic pattern is reflected biogeographically and points to a common African origin for the subfamilies. The following migrations, initially those of (most likely) proto-acridines, are further suggested by the data: 1) movement from Africa to South America establishing genera of that continent's Gomphocerinae (e.g., Jagomphocerus) and Acridinae (e.g., Metaleptea), followed by incursions into North America, leading to species such as Amblytropidia mysteca; 2) a somewhat circuitous sequence of events involving a reverse migration from South America to Africa (establishing genera such as Thyridota) with ensuing dispersals to Eurasia (forming genera such as Myrmeleotettix) and to North America (leading to, for example, Brunneria and the bulk of that continent's Gomphocerinae); 3) almost simultaneous with the first event, migration of other early acridines from Africa to Eurasia, establishing the latter continent's Oedipodinae (e.g., Angaracris). Subsequent dispersals to North America and the South Pacific led to genera such as Camnula and Austroicetes, respectively.