1. Sheep myiasis was investigated in certain districts in Ayrshire, Arran and Argyllshire.
2. Larvae from cases of myiasis were collected and bred out in flyproof apparatus.
3. The fly season was found to last approximately from May till September, reaching its height in July and August.
4. The western districts were found to be the most heavily affected.
5. The flies were found to be partial to low-lying, sheltered ground, especially where much bracken was present.
6. The methods of carcass burial were found to be primitive and inadequate. In most of the farms dipping was carried out without sufficient attention to cleanliness and adequate time of immersion.
7. The hibernation of various species of blow-fly was studied. They were found to pass the winter as prepupae, pupation never occurring normally till April or May.
8. Several species of carrion-feeding blow-fly besides Lucilia sericata were found to be causing secondary myiasis, occasionally and in small numbers, in certain districts, mainly in the west. The species involved were: Lucilia caesar, L. illustris, Protophormia terraenovae, Calliphora erythrocephala, C. vomitoria and Muscina pabulorum. Four of these species Lucilia illustris, Protophormia terraenovae, Calliphora vomitoria and Muscina pabulorum have not previously been recorded from sheep. Records of cases in which these flies occurred are given.