In wit^HA4/wit^HA5 mutant larvae, the number of synaptic boutons seen on dorsal muscle 1 are approximately reduced by 55% compared to wild-type. The muscle surface area is on average 12% smaller. Muscles 2, 9 and 10 also exhibit similar phenotypes. Neuromuscular synapses in wit^HA2/wit^HA5 mutant larvae have active zones with T-bars, synaptic vesicles both free within the bouton and clustered around the T-Bars, and other features that appear wild-type. A smaller population of vesicles larger and distinct from the synaptic vesicles is seen. An unusual ruffling of the presynaptic membrane in active zones, about 44% of the presynaptic membrane is detached from the postsynaptic membrane. A novel electron dense structure associated with a tight cluster of vesicles are seen; about 2.4 of these are seen per bouton.