Iowa Butterfly Forecast for June 2023

Giant Swallowtail (Papilio cresphontes)

As I sift through the multitude of emails flooding my inbox each day, it feels peculiar to admit that something has been missing this spring. Every year, I eagerly anticipate the arrival of the "Butterfly Forecast for Central Iowa." It serves as a delightful reminder that butterflies and other insects will soon grace our surroundings, and in my opinion, every day is made better by their presence. However, this winter brought the unfortunate news of the passing of Harlan Ratcliff, the creator and long-time writer of the "Butterfly Forecast of Central Iowa," in November. Harlan and I have collaborated on numerous projects over the years. He was a frequent presenter at Day of Insects at Reiman Gardens, even in its inaugural year. He actively participated in the Iowa Butterfly Survey Network as one of my surveyors. Furthermore, he volunteered as one of my Butterfly Wing docents at Reiman Gardens on a regular basis. Harlan's passion for nature will be sorely missed by me and many others. In light of his legacy, I have decided to carry on where Harlan left off, albeit with a slight rebranding.

Firstly, I feel compelled to apologize to those residing in southern and northern Iowa. The original butterfly forecast was designated "for Central Iowa" for a reason. Temperature and weather conditions play a significant role in determining when insects appear and disappear each year. To those in the southern part of the state, my forecast may lag a bit behind, while those in the north may need to exercise patience before witnessing their arrival. Moreover, given the size of Iowa, there are several butterfly species that are not found statewide. Consequently, there may be instances when I discuss species that are not present in your particular region. Now that we've attended to these logistical matters, let's delve into the heart of the forecast.

Summer Azure (Celastrina neglecta)

One of Iowa's largest butterflies, the Giant Swallowtail (Papilio cresphontes), is approaching its first peak flight period. From the last week of May through the first two weeks of June, you have the best chance of catching sight of this majestic butterfly early in the season. Giant Swallowtails are robust fliers and can often be spotted nectaring on flowers. However, your best opportunity to encounter them may lie within wooded habitats where prickly ash shrubs thrive. Over the years, I have raised these butterflies several times, and it never fails to bring a smile to my face as they progress through their later instars, resembling avian droppings.

Although the Spring Azure (Celastrina ladon) may have bid farewell for the year, the Summer Azure (Celastrina neglecta) are on their way. Now, I'll let you in on a little secret—I can't tell these two species apart. I mean, seriously, even after examining a box of pinned specimens (which I have done), the only way I could sort them was by looking at the collection date. Apparently, there has been some research indicating that a noticeable difference in the scales on their wings can be discerned under an electron microscope. Unfortunately, that information doesn't help much when you're observing these small butterflies fluttering about in the field. Expect them to start making their appearances in earnest during the second week of June.

Red Admirals (Vanessa atalanta)

While I don't have a favorite butterfly—each possesses its own unique charm—I must admit that I find myself devoting a considerable amount of time discussing Red Admirals (Vanessa atalanta). As a child, I always took pleasure in observing their territorial behavior. Over the years, I have nurtured hundreds of Red Admiral caterpillars through their various stages, and for the past decade, I have been conducting a mark-recapture study on them in my backyard, with the invaluable assistance of my children. They truly are fascinating butterflies, and I always keep an eye out for them. Based on the reports of first sightings this year and the numbers I have been hearing, it seems we are in for a thriving population of Red Admirals this summer. If you happen to take an evening stroll during the third week of June, there's a high probability that you will encounter one or two Red Admirals along the way.

Allow me to conclude by sharing a passage from Harlan's March-April 2022 Butterfly Forecast:

"I have been producing this butterfly forecast for numerous years now. My intention is not only to impart some knowledge about these magnificent creatures but also to share the passion I feel for them. Yet, it's not just about the butterflies. Take a walk through the woods and relish the fragrance of damp leaves and mosses. Listen to the melodic songs of birds and the rhythmic chorus of frogs. Seek out the blossoming spring wildflowers—they will soon grace our surroundings. While you immerse yourself in nature's embrace, keep an eye out for the enchanting presence of butterflies."

All of Harlan's 2022 Butterfly Forecast can be found at

Wishing you all a happy butterfly season,

Nathan Brockman

Director of Entomology, Reiman Gardens


Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on May 23, 2023. The information contained within may not be the most current and accurate depending on when it is accessed.