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Abstract. Third instar larvae of A.rufipes were found in short vertical shafts in the soil beneath horse dung and they entered the underground brood masses of G.spiniger when these occurred beneath the same deposit of dung. A.rufipes larvae excavated shafts (60–80mm deep) beneath dung in cages. Just before diapause they burrowed down to the floor of the cage. Burrowing was inhibited in compact soil and in very dry soil. The feeding larvae were attracted to dung and to moisture and they readily attacked other larvae with their mandibles. In cages which contained G. spiniger nests the A.rufipes larvae burrowed down to feed on the G.spiniger brood masses. G.spiniger eggs and larvae did not act as attractants but they were often destroyed if the A.rufipes larvae encountered them by chance. In cages which contained G.stercorarxus nests A.fossor larvae burrowed down to feed on the brood masses if no dung was provided at the surface. This non‐obligatory parasitism arises from the normal behaviour of the larvae and is usually of trivial significance, but under certain conditions the protected environment of an underground nest may favour the survival of the invading larvae.

1. Dung beetle lifestyles are reviewed. Most Scarabaeinae lay their eggs in dung masses that are packed into underground chambers, but Coprini and Scarabaeini typically lay their eggs in free-standing brood balls and it is in these tribes that parental care of the brood has evolved.2. Brood balls are constructed by aggregating fragments of dung. This technique is derived from the method of gathering dung at the surface. Larvae developing in brood balls are better protected against dehydration and parasite attack. The repair technique of Scarabaeine larvae preadapts them to life in brood balls.3 . Parental care by Copris lunaris depends on appropriate responses by the female to the brood, and it has the selective advantage of protecting the brood against parasites. Preadaptations for parental care in 'non-brooding' Coprini are discussed.4. Variations in the basic Copris nesting behaviour are summarized. Similar variations can occur spontaneously in C.lunaris and can also be released by unusual circumstances. . C.lunaris females could in principle cooperate but certain factors haveprevented this social evolution. The significance of the transient cooperation with the male beetle is discussed.

1. The activity of thymidine kinase in rat liver supernatant decreased with development to a value in the adult that was 1% of that in the 17-day foetus. 2. The foetal enzyme was more stable than the adult to gel filtration on Sephadex G-25 at 0 degrees . 3. The greater stability of the foetal enzyme to incubation at 45 degrees was attributable to the presence of higher concentrations of nucleotides in foetal liver supernatant. 4. The K(m) values for foetal and adult enzymes were approx. 2.5mum- and 2.1mum-thymidine respectively. 5. The foetal enzyme was more sensitive to inhibition by thymidine triphosphate. 6. The decline in enzyme activity during the neonatal period was correlated with a shift in the enzyme properties from the foetal to the adult type, and may reflect the decrease in the proportion of haemopoietic tissue in the liver.