An adult Tachinid Fly looks ugly, but it's the young fly larva that is most grotesque. It feasts on a caterpillar's insides, saving the most important organs for the last meal.
Tachinid Fly larvae are efficient pest controllers for certain moth species. This particular species parasitizes some tiger moth and also some skipper species. Because of this particular diet in their larval stage, some species of Tachinid Flies have been deliberately imported from other areas to control destructive moth populations here in North America. However, Tachinid Flies also parasitize caterpillars of much-loved butterflies like the Monarch. They are a threat to those raising Monarchs, infecting at the caterpillar stage and killing in the chrysalis.
A female Tachinid Fly will lay one or two fertilized eggs on, or near, a caterpillar. The caterpillar may even inadvertently eat the eggs as it chews through a leaf that the eggs were laid on. The fly larvae may also latch on to a passing caterpillar and promptly eat a hole into its body. It then slowly feeds on the caterpillar's internal parts. Once the fly larva is mostly developed, it will consume the caterpillar's most necessary organs and the caterpillar dies. The fly larva will exit its dead host and move to the ground where it will dig a hole to pupate in. Flying adults emerge from the ground. These spiky, hairy adults drink nectar.
This particular species of Tachinid Fly can be found on flowers, in fields, parks or gardens during the summer and autumn. Look for big red eyes and spiky hairs on the abdomen to help differentiate them from House Flies.
Scientific Name: Juriniopsis adusta
Fly or Mosquito
Size (Adult; Length): 9mm to 15mm (0.35in to 0.59in)
Note: An insect's reach is not limited by lines drawn on a map and therefore species may appear in areas, regions and/or states beyond those listed above as they are driven by environmental factors (such as climate change), available food supplies and mating patterns. Grayed-out selections indicate that the subject in question has not been reported in that particular territory. U.S. states and Canadian provinces / territories are clickable to their respective bug listings.