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The changes in total haemocyte counts (THC) in relation to sex, development, ecdysis, and hot-water fixation have been studied in Halys dentata (Hemiptera). Whereas statistically there is no difference in the THC of the two sexes, the THC differs in the immature stages and adults. There is a gradual increase in counts during metamorphosis. The fixation of insects in hot water before withdrawal of haemolymph abruptly affects the THC and it shows a significant increase in the number of haemocytes. Studies made in relation to ecdysis show that the THC slightly decreases 24 hr before ecdysis, whereas after ecdysis it abruptly falls and then rises again during the middle part of the instar.

An in vivo perfusion technique with tritiated water was used to study the efflux of rectal lumen water and the influx of haemolymph water in the cockroach, Leucophaea maderae . No isotopic effects on tritiated water absorption through the rectal wall were observed. Concentrations of a non-diffusible solute trehalose ranging from 0·15 to 0·6 M did not differ in their effect on absorption of initial lumen water which was very rapid in the first 30 min. Influx of unlabelled haemolymph or tissue water was also rapid, preventing any net reductions in lumen volume in this time. When no solutes were perfused into the lumen, absorption was increased but influx of water still occurred at a reduced rate, apparently against a concentration gradient. The rapid turnover and cycling of water through the rectal wall and chamber in contrast to the long time necessary to dry the faecal pellet may be a way to facilitate reabsorption of small, metabolically useful, solute molecules including amino acids and monosaccharides filtered from the haemolymph by the Malpighian tubules or occurring as digestion residues. The process is relatively independent of a wide range of osmotic pressures in the lumen.

A single ventral oesophageal diverticulum is present in adult Papilio aristolochiae (Lepidoptera: Papilionidae), and a histologic development of this has been studied in detail. The larval oesophageal valve from which the ventral diverticulum arises, has been divided into 5 different regions. The fate of all these regions has been followed during pupation. Cells of the anterior imaginal ring in the pupa divide mitotically and furnish the cells of ventral evagination, which forms the ventral diverticulum. The ventral evagination grows as a result of increase in the number of cells and also cell enlargement. Regions 4 and 5 degenerate completely in the adult, and the degenerated cells are thrown into the body cavity.