Cytogenetics of Orthopteroid Insects

The effect of temperature on chiasma frequency

“…This is the chiasma frequency for the autosomes only. Supernumerary chromosomes of the type which vary in number from cell to cell of the one animal (White, 1952 ;Rees and Jamieson, 1954), were present in all but three animals, and their number and the number of chiasmata they formed were recorded for each cell scored. The number of supernumeraries per cell bore no simple relation to the chiasma frequency of the autosomes within most animals, and the number of supernumeraries bore no relation whatever to the mean chiasma frequency of the autosomes when all animals were considered.…”

Evolution of Caryotype in an Interesting Species of Grasshopper, <i>Tristria pulvinata</i> Uvarov

“…The pairing of the two supernumeraries although very rare (Ray-Chaudhuri and Guha 1955) has been reported in Trimerotropis spaysa (White 1951). But unlike in T. sparsa where the two supernumeraries move frequently to one pole, the segregation of the particular pair of D chromosomes of Tristria pulvinata to opposite poles was as regular as any other pair of autosomes.…”

“…In Aidemona azteca (White 1951) the male individuals possess 21 chromosomes which could be accounted for by the presence of one pair of metacentric chromosomes in place of four acrocentric ones. Two or three centric fusions lead ing to the reduction in chromosome number have also been occurred in Aleuas vitticoli, A. lineatus (Saez 1932(Saez , 1935(Saez , 1945, and in different species of Myrmeleotettix and Chorthippus (see White 1954).…”

Cytogeography and the evolutionary significance of B chromosomes in relation to inverted rearrangements in a grasshopper species

“…Like Drosophila, the genus Trimerotropis constitutes another example of "karyotypic orthoselection", because it is cytologically characterized by a high incidence of fixed and/or polymorphic inversions (White, 1973;Hewitt, 1979;John, 1983). Most of these grasshoppers inhabit arid regions from western North America, although some species as T. ochraceipennis and T. pallidipennis also reach South American lands (White, 1951). According to White (1973), the colonization presumably descended along the Andean dry lands of South America and was probably made by North American T. pallidipennis, carrier of a basic chromosome arrangement.…”