Search results for "Instar"
showing 6 items of 56 documents
Nachweis von h�utungsaktiven Stoffen in isolierten Prothorakaldr�sen und Oenocyten beiBombyx mori w�hrend des 5. Larvenstadiums
1977
The content of moulting hormones has been determined in homogenates of isolated prothoracic glands and oenocytes during the 5th instar of the silkworm,Bombyx mori by means of the Calliphora bioassay. Prothoracic glands show variable activity in the production of moulting hormones, reaching a maximum near the end of the larval period. Comparable activities, but at higher levels, could be demonstrated in oenocytes. Controls with doubled quantities of tissue produced in a proportionate reaction in the bioassay. Fat bodies were inactive. Prothoracic glands and oenocytes incubated together resulted in a slower pupation index than would be expected from the sum of single determinations of oenocyt…
Carotenoid-based colour polyphenism in a moth species: search for fitness correlates
2007
Carotenoid-based integumental coloration is often associated with individual performance in various animals. This is because the limited amount of the pigment has to be allocated to different vital functions. However, most of the evidence for the carotenoid-based trade-off comes from vertebrate studies, and it is unclear if this principle can be applied to insects. This possibility was investigated in Orgyia antiqua L. (Lepidoptera: Lymantriidae). The larvae of this species are polyphenic in their coloration, varying from a highly conspicuous combination of yellow hair tufts on black background to cryptic appearance with brown hair tufts. The conspicuous larvae are aposematic, advertising t…
Determination of biological characteristics of Tunisian Artemia salina populations
2012
In this study, Artemia salina cysts collected from four Tunisian hypersaline environments were characterized using biometrical, biological and biochemical descriptors. Biometrical analysis revealed that the mean diameter value ranged from 220.25 to 237.76 μm, for the untreated cysts, from 199 to 224.52 μm for decapsulated cysts and that the chorion thickness ranged from 6.62 to 10.58 μm. 48 h after hatching, Artemia from Sebkha El Meleh, Sebha Moknine, Sfax saltworks and Sahline saltworks presented a hatching percentage of 52.7%, 53.75%, 70.16% and 43.74%, respectively. The length of the freshly hatched instar I nauplii varied from 429 to 449.34 μm. The fatty acids profile showed that the n…
Larval Arrest in Development of Tribolium castaneum (Coleoptera: Tenebrionidae)
1986
Arrested larval development (in the last larval instar) of part of the total larval population has been detected in moderately crowded situations (40 larvae in 2 g food) in Tribolium castaneum (Herbst) cultures This phenomenon is the same found previously in highly crowded cultures of Drosophila melanogaster (Meigen) and other related species. The arrest may be viewed as a mechanism of physiological adaptation of organisms to competitive situations.
Postembryonic development of Zophobas atratus Fab. (Coleoptera: Tenebrionidae) under crowded or isolated conditions and effects of juvenile hormone a…
1995
Abstract Pupation in Zophobas atratus is dependent on isolation and this provides a model for study of the onset of metamorphosis in beetles. We have analyzed the effects of isolation vs grouping on certain developmental parameters; the number of larval instars; their duration and weight. Sex differences were detected, such as the occurrence of regressive moults in females. Moreover, the development of Z. atratus is discussed in relation to Tenebrio molitor , the physiological timing of which appeared in part extendable to Z. atratus . Experiments show that 4–6 days of isolation are required for commencement of metamorphosis, as indicated by an immobile crooked posture observed at the end o…
Field application of the juvenile hormone analogue fenoxycarb against hopper bands of Locusta migratoria capito in Madagascar
1997
Summary Field trials have been carried out to examine the suitability of the JHA fenoxycarb in locust control. Laboratory tests have shown that a variety of JHAs, including fenoxycarb, applied to last instar larvae increased mortality, induced morphogenetic defects during metamorphosis, reduced fertility and provoked solitarisation of gregarious hoppers. The phase shift was indicated by green coloration and the acquisition of morphological and behavioural characteristics typical for solitary locusts. The present field experiments should clarify whether or not the effects observed in the laboratory are also observed with hopper bands in their natural habitat and if swarm formation and emigra…