Insects Active during the day

Turnip Sawfly

Athalia rosae

iNaturalist Wikipedia

The Turnip Sawfly is a jewel-toned visitor to the summer garden, easily recognized by its glowing orange body and dark, velvety larvae. A fascinating example of garden biodiversity, it is a must-see for any backyard entomologist.

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Quick Identification

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Size

Adults: 7–8 mm (0.28–0.31 in) long; Larvae: 18–25 mm (0.7–1.0 in) long

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Colors

Adults are vibrant orange with a black head and black dorsal patches on the thorax; larvae are dark velvety green to charcoal gray, appearing nearly black.

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Key Features

Bright orange body contrasting with a jet-black head
Black 'stigma' mark on the leading edge of translucent wings
Larvae have a caterpillar-like appearance but with 6-8 pairs of prolegs
Slow, hovering flight pattern near ground level

When You’ll See Them

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Activity pattern Active during the day

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Peak hours 10 AM - 4 PM

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Season May-September

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Diet Adults feed on the nectar of flowering plants, especially those with shallow blossoms like Hogweed and Tansy. Larvae are specialists that eat the foliage of the Brassicaceae family, including turnips, radishes, cabbage, and rapeseed.

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Habitat Found in suburban gardens, allotments, agricultural fields, and wildflower meadows where cruciferous plants are present.

Behavior

The Turnip Sawfly is most active during warm, sunny days when adults can be seen flitting between nectar sources and host plants. Unlike many other garden insects, they have a somewhat clumsy, slow flight, making them easier to observe. The adults are primarily focused on mating and locating suitable brassica leaves where the female uses her saw-like ovipositor to cut slits and deposit eggs.

The larvae are the most conspicuous stage of the life cycle, often found in large groups on the undersides of leaves. They are voracious eaters and can quickly skeletonize a plant, leaving only the tough veins behind. When disturbed, the larvae often adopt a distinctive 'S' shape or drop to the soil to hide in the debris. In a single season, they can produce up to three generations, meaning their presence in the garden can persist from early summer through the first frosts of autumn.

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Camera Tips

To capture the Turnip Sawfly on camera, you need to focus on its favorite buffet: the vegetable patch. Position your camera near 'sacrificial' plants like wild mustard or radish that show signs of leaf nibbling. Because these insects are small, a macro lens or a camera with a very close focal point is essential. Aim the lens at the undersides of leaves where larvae congregate, or at the yellow flowers of brassicas which act as a natural magnet for the orange adults.

Lighting is your best friend when filming this species. They are most active in direct sunlight, which provides the high shutter speeds needed to freeze their wing movement. Set your camera to a high-frame-rate video mode if you want to capture their unique 'sawing' egg-laying behavior. If you are using an AI-powered camera, ensure it is positioned no more than 12-18 inches from the foliage to trigger the motion sensors effectively.

For the best results, look for them during the peak of summer (July and August). If you notice small, dark, caterpillar-like creatures on your turnips, that is the time to set up your gear. Using a tripod for stability and a narrow aperture will help keep the entire insect in focus, allowing you to see the intricate black markings on the orange thorax that distinguish this species from other sawflies.

Similar Species

Species that look similar or are commonly confused with Turnip Sawfly.

Mustard Sawfly

The Mustard Sawfly (Athalia lugens) has more extensive black markings on its legs and a different wing vein pattern.

Berberis Sawfly

Much larger and usually associated with Barberry plants; it lacks the vivid orange thorax of the Turnip Sawfly.

Large White Butterfly Larvae

Butterfly larvae have only 5 pairs of prolegs, whereas sawfly larvae have 6 or more pairs.

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Frequently Asked Questions

Turnip Sawfly adults are strictly diurnal and are most active during the warmest part of the day, typically between 10 AM and 4 PM, when the sun is brightest.

To attract them, plant a variety of brassicas such as turnips, radishes, or kale, and leave some to go to flower. They are also highly attracted to yellow-colored traps or flowers.

Adults drink nectar from wild flowers like Queen Anne's Lace. The larvae eat the leaves of plants in the mustard family (Brassicaceae), often leaving only the leaf veins.

Yes, they are very common in suburban gardens and allotments, especially where vegetables are grown or where wild mustard and radish are allowed to grow.

Look for the specific combination of a bright orange abdomen and thorax with a completely black head. The larvae are also distinctively darker (nearly black) compared to the green larvae of many other sawfly species.

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