Externally above the mouth and oral lobes, the larva has two dorsal lobes, each with a prominent projection called the dorsal organ. This is greatly innervated and primarily serves as an olfactory receptor.
Below the dorsal lobes is a pair of terminal lobes bearing the terminal organ, and closer to the mouth is a pair of ventral organs. The dorsal, terminal, and ventral organs are the three major groups of sensory receptors for the larva, enabling it to perceive its environment and move to optimal sites for food and survival.
The terminal organ receptors are mostly contact chemoreceptors, as are the ventral organ receptors.
The ventral organ probably serves the function of gustatory perception to aid in the selection of suitable foods by the larva.
Internally, three pairs of ganglia underlie these three pairs of anterior sensory organs. These organs provide the larva with the sensory perceptions needed to survive by seeking the most suitable microhabitat based on odor, temperature, moisture, and chemical constituents.
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