Long Hot Summer of '76 No 2: The iris Season...

 

The 1976 Purple Emperor season was one of the greatest of the 20^th century, building on good seasons in 1974 and, especially, 1975. However, it was an unusually short season, with numbers nosediving after three heady heatwave weeks – as was the case in 2025.

Indeed, the similarities in adult behaviour between the 1976 and 2025 flight seasons are immense. 

Nationally, the first male of ’76 was seen at Bookham Common, Surrey, by leading Emperorphile KJ Willmott on June 24^th. That equaled the record earliest appearance listed by IRP Heslop, though Heslop’s diligent searches through the entomological literature had somehow missed the incredible summer of 1893, when the butterfly was ‘well out’ in the New Forest ‘by early June’ and a male was taken by a Marlborough College boy on June 10^th.

The ’76 season, like that of 2025, was dominated by heatwave conditions. Indeed, 1976 brought what was then the UK’s warmest June on record. From June 24^th till July 8^th (inclusive), heatwave conditions prevailed: the temperature reached or exceeded 32C somewhere in southern England for 15 consecutive days. Tarmacked roads melted – I know, I was on a bicycle. 

For the record, there was extensive rain in the Purple Empire on June 19^th-20^th; thereafter rain fell in much of the Empire on July 9^th, 13^th, 16^th and 20^th, some of it thundery. Thereafter, there was virtually no rain until the weather broke at the end of August – and many sallows wilted, along with veteran beeches. The drought had, though, started way back in the spring of 1975. Then, after a hot dry summer, the autumn and winter rains failed – in stark contrast to the autumn and winter of 2024-25 (and indeed 25-26).

All this meant that there was little if any moisture for midsummer butterflies fifty years ago. In early July ‘76 Emperors, of both sexes, descended to the parched rides in early morning (8.30-9.30) to probe for moisture amongst the grasses, accompanied by numerous Purple Hairstreaks. This phase, though, lasted barely a week.

In those days there was little if any dog poo on the rides, as most Emperor woods discouraged public access – you had to hold an Access Permit to enter many Forestry Commission woods. 

Instead, there was a super-abundance of ‘honeydew’, the sticky secretion of aphids. During the midsummer heatwave, the oaks literally dripped with it: Emperors, Purple Hairstreaks and, curiously, Meadow Browns feasted on it high up. Also, Emperors, as in 2025, sought oak sap ardently – and even human sweat: I had a male feed on me on June 29^th, and later watched a pair feeding together on creosote!

In Alice Holt Forest, E Hants, where I was centred, the first White Admiral and Silver-washed Fritillary appeared only on June 21^st, and the first Emperor on the 25^th. I noted the first definite Empress on July 1^st. By July 6^th, they were busily egg-laying – selecting heavily shaded isolated sprays beneath the main sallow canopy. 

On July 10^th, I watched a female ab. lugenda (‘semi-iole’ in the language of the day), at 9.40 and again at 1.30. She was seen once more, in the same sallow glade, on July 14^th. 

On July 11^th I watched a courtship flight, which quickly became a treetop mating that lasted for 3 hours 35 minutes (and must have been the female’s second mating, for she was distinctly worn). 

Suddenly, around July 12^th numbers plummeted, and they were gone. I saw my last on July 18^th, and thereafter concentrated on finding eggs (which hatched fast in the heat) and larvae.

That summer saw a resurgence of old-fashioned butterfly collecting – grown men in shorts, running around with nets. Iris, as it then then called was the main target species. Nets clashed at the few well-known localities, notably Lodge Inclosure of Alice Holt Forest, Kingspark Wood (then FC) in Chiddingfold Forest, and Hell Coppice & Shabbington Wood in Bernwood Forest, Bucks/Oxon. That summer also saw the birth of butterfly photography. 

On several occasions I encountered the legendary Baron Charles de Worms, Heslop’s closest ally. At one stage he was dressed in a string vest, Boy Scout shorts straight out of the Baden Powell era, and corps boots – he was rubbing rancid Danish Blue cheese into a gatepost, as a bait for iris. We shared an entomological friend, a retired GP, Dr John Holmes. de Worms was a delightful man, but it was impossible to get any locality information out of him, and he shed little light on Heslop, my boyhood hero.    

The good news is that those of us who lived through the 2025 Purple Emperor season have a pretty good idea of what the 1976 season was like. 

What matters now, of course, is what the 2026 Emperor season will be like. Watch this space, for one of these years iris will be on the wing in May…