File:Megastigmus aculeatus - Rose Seed Wasp.jpg

English: Happy Wing Wednesday everyone.

Rose-seed Megastigmus is a seed-infesting wasp that is common in homes and establishments where dried flowers and potpourri containing rose hips are found. Generally, the wasps are noticed during the winter months when the adults fly to windows or lights. Although these tiny wasps are very easy to identify, their small size frequently contributes to misidentification.

The adults vary greatly in size and coloration. Wasps that are raised from a wild or multiflora rose are considerably smaller than those raised from the larger cultivated rose. Typically, they are approximately 3 mm in length and are mostly yellow in color. The females carry an ovipositor that curves upward from the last abdominal segment and is about the same overall length as the wasp. Brown patches are on top of the head surrounding the ocelli, on the sides of the thorax, and on the dorsal side of the abdomen. The elbowed antennae are also brown and have eleven segments. The males are typically smaller, darker to nearly black in color, and do not have an ovipositor.

The eggs are oviposited into rose hips during June and July. The larvae feed entirely within the rose seed and can grow to 2.8 mm or slightly more than 1/10 inch in length. The size, however, is greatly dependent on the size of the seed. The larvae become fully grown in the fall and remain within the seed casing until the following spring when they pupate. The adults emerge from the seed by chewing small openings in the seed in early summer. This timing is altered when rose seed is brought into the home over the winter months.