A study of the digestive processes and some related aspects of the biology of two species of scarabaeidae (Typhaeus typhoeus and Oryctes boas).

Little is known about the digestive processes in insects which feed on dung. They are of interest because the main components of the dung are cellulose and lignin and these substances are extremely difficult to digest. In this research the larvae and adults of Typhaeus typhoeus L. and the larvae of Oryctes boas Fabr. were studied. The composition of the food of the insects was investigated. The gut and mouthparts were examined to find how they are adapted for coprophagy. The micro-organisms in the gut were studied and compared in type and numbers with those in the food. The enzymes in the gut were investigated. Experiments were carried out to find what substances are removed from the food in the gut, and how long the passage of food takes. The food of Typhaeus typhoeus larvae contains a particularly high percentage of cellulose and lignin but the larvae cannot digest these substances. They feed by digesting micro-organisms which live in the dung. Bacteria are cultured in the hindgut sacs and provide an additional source of food. Some cellulose is digested in the gut by bacteria, and the digestion products are absorbed by the larvae. The food of Typhaeus typhoeus adults contains a relatively high percentage of substances other than cellulose and lignin and the insects produce enzymes which digest these. They can digest micro-organisms but are less dependent on them than the larvae. Oryctes boas larvae are found feeding on many different, substances. They utilise the easily digested substances in their food, if these are present, but they can also digest cellulose. It is uncertain whether cellulase is produced by the insect or by symbionts which have not been detected. The larvae digest bacteria which are cultured in the hindgut; these bacteria digest a little cellulose and hemicellulose and the larva absorbs the fatty acids produced.