Abstract: The allometry, growth and activities of the gastric caeca of Zonocerus variegatus(L.) were determined to find out the functions of its posterior caeca which are unknown. This was done by dissecting out the gut and measuring the main gut regions and the gastric caeca in the six nymphal stages and adult. The gut consists of three main regions; the crop, ventriculus, with gastric caeca attached at anterior rim, and the hindgut. Each set of caeca consists of a long anteriorly pointed arm and a short posteriorly pointed arm. The growth of the caeca relative to the main gut was allometric. The anterior caeca had higher growth ratios than the posterior caeca and both were highly correlated. The relationship between gut and caeca mean length was highly significant. The mean gut length and age were significantly correlated with growth rate exponent <1 indicating a decreasing growth increment with age. The mean caeca length and age were highly correlated with growth exponent >1 indicating an increasing growth with age. Females had higher mean lengths than males and this was highly significant (P<0.05). Males had higher growth ratios than females except at growth centres. The growth patterns of the caeca for wet and dry seasons were similar with a single growth centre. But the mean length of the caeca was significantly different between wet and dry season’s insects from the fourth instar to adult. The posterior caeca was considered a complementary structure to the anterior caeca. They perform the same function of digestion and absorption of food. The posterior caeca is concluded additional device to increase the surface area of the ventriculus to cope with low nutrient status of herbivory.

Key words: Zonocerus variegatus; gastric caeca, growth gradi ent, function