It is the larval stage of the syrphid fly that is an insect predator. Variously colored, the tapered "maggots" crawl over foliage and can daily down dozens of aphids. Syrphid flies are particularly important in controlling aphid infestations early in the season when its still too cool for lady beetles and other predators.
A few species of syrphid flies, such as the narcissus bulb fly, develop by feeding on and tunnelling plant tissues. These plant feeding syrphid flies often develop into large, stout-bodied flies that may resemble bumblebees.
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