A rearing method, based upon an artificial diet, has proved successful in establishing laboratory colonies of 36 species of the genus Euxoa. The diet is described, along with methods for controlling disease, particularly by the use of antimicrobial agents.Many of the 36 species of Euxoa have not been reared before and their habits and life histories are little known. The data derived from their development under laboratory conditions and which can be related to seasonal distribution are recorded. Particular emphasis is given to the overwintering stage and to the occurrence of an aestivating stage.

Plants from three clones of big trefoil (Lotus uliginosus Schkuhr) having low, medium and high concentrations of tannin in their leaves were subjected to growing conditions with normal (20°C) and high (30°C) temperature regimes.Plants were tested every 3 weeks for foliar condensed tannin content using the vanillin-HC1 and the butanol-HC1 assays. Plants from clones growing under high temperatures matured more quickly and by 14 days had condensed tannin levels substantially greater than plants from the same clones grown under normal temperatures. Clones remained consistent with respect to their parental tannin levels throughout two trials. Leaves from high-temperature clones suffering additional nutrient stress symptoms had very low levels of foliar condensed tannins and cross-sections of chlorotic leaves revealed an absence of large tannin vacuoles. It is concluded that high-temperature stress can induce the formation of additional condensed tannin in the leaves of this species.

Haemopoiesis in Lepidoptera is doubtless accomplished to a large extent by mitosis of the circulating haemocytes. but there are some anomalies with regard to certain classes. Granular haemocytes and spherule cells are the only classes that divide frequently enough to account alone for their continued increase in numbers. Prohaemocytes divide frequently, but their numbers do not increase markedly. There is little doubt that they differentiate exclusively to plasmatocytes, which rarely divide themselves but continue to increase in numbers during larval life. An increase in plasmatocyte size and numbers after the fourth instar, when the mitotic index of prohaemocytes is declining, suggests an alternative source as well. Oenocytoids never divide, and undoubtedly derive from a separate source.

Haemopoietic organs were found in association with the wing discs in 15 species of Lepidoptera examined. The organs were shown to contain small stem cells organized into islets which generate either oenocytoids or prohaemocytes–plasmatocytes. The great majority of islets comprised the latter, and there was evidence that prohaemocytes transformed into plasmatocytes. A decline in the size of the haemopoietic organs during the fifth instar indicated a major release of cells, and correlated with changes in the complement of circulating haemocytes.Total haemocyte counts were reduced in the posterior section of larvae ligatured in the middle, but differential counts showed a more marked decline in prohaemocytes and plasmatocytes than in other classes of haemocytes. Larvae with two or more ligatures usually showed higher prohaemocyte and plasmatocyte counts in the parts of the body that included the haemopoietic organs. Inclusion of the head and prothorax in such sections resulted in still higher counts of prohaemocytes and plasmatocytes as well as higher mitotic indices.The concept that there is a dual origin of haemocytes, from division of cells in circulation (granular and spherule cells) and from the haemopoietic organs (prohaemocytes, plasmatocytes, and oenocytoids) is presented.

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