The variety of flowers brings a profusion of insects.

Gatekeeper, male

Butterflies are one of the main attractions and more than 25 species have been recorded on each site. The majority are fairly common, widespread species but some of these such as the Meadow Brown, Gatekeeper and Brimstone can often be seen in large numbers.

Unfortunately, many species associated more specifically with chalk grassland such as the Dingy Skipper, Grizzled Skipper, Marbled White, Small Blue and Chalkhill Blue disappeared when the dyke became covered with scrub.

Chalkhill Blue, male

However following a successful habitat management programme, Chalkhill Blues have now recolonised parts of Fleam Dyke, both north-west and south-east of the A11. First recorded in August 2005, several hundred of these silvery blue butterflies can now be seen during the peak season in late July and early August.  On the Roman Road, Chalkhill Blues were first seen in 2007 and since that date a small population has been maintained.

Marbled White

Marbled Whites were seen previously only as occasional visitors, but since 2019, have re-established populations on both sites.  After many years of absence, a singe Small Blue was recorded on the Roman Road in 2022.   The Dark Green Fritillary, another uncommon species, can be seen on Fleam Dyke most years in July.  The abundance of violets, the larval food plant of the Dark Green Fritillary, makes it a suitable habitat for this species.

In May, another less common butterfly, the Green Hairstreak can be seen on Fleam Dyke in the early part of the season on both sides of the A11, often basking in the sunshine in the remaining areas of scrub. Colourful day-flying moths such as the Six-spot Burnet and Cinnabar are also seen during the summer months.

Thick-legged flower beetle

Other insects include bumblebees, a range of solitary bees and wasps, hoverflies, beetles, crickets and grasshoppers. The numerous anthills, particularly on Fleam Dyke, are evidence of large numbers of meadow ants, which are only found in areas of old and undisturbed grassland.

For further information, see Butterflies; Butterfly Monitoring; and Butterfly transect data for 2023.

Download lists of insect species here.