Connecticut Butterfly Association


A guide to identifying the Azure (Celastrina) species

occurring in Connecticut

by Lenny Brown


Introduction

According to the Connecticut Butterfly Atlas, four species of azures are found in Connecticut, the Spring Azure (C. ladon), the Summer Azure (C. neglecta), the Cherry Gall Azure (C. serotina) and the Appalachian Azure (C. neglectamajor).

One of these species, the Appalachian Azure, is restricted to the western edge of the state along the New York state border and is closely associated with it larval food plant, Black Cohosh (Cimicifuga racemosa).  As a result, observers looking at butterflies CT will rarely, if ever, see Appalachian Azures.  However, the other azure species are widely distributed across the state and distinguishing the various azure species can be a challenge, particularly in the spring when three species of azures are on the wing and there is some overlap in the flight times of these species. 

Therefore, I wrote this article to assist observers in identifying the three species of azures that are commonly found in the state.  It is important to note that there are significant limitations to this guide because it is only useful for identifying males and it assumes the observer can see the upper side of the butterfly. 

I only included males, because it can be very challenging to identify females, even in those situations where the observer is able to net the insect and observe it in hand.  Female azures can be distinguished from males by the broad black band on the outer edge of the forewing.  Males lack that broad black band.  To be able to identify male azures, it is important to see the upper side of the insect since that is where you will find the field marks that are most useful for distinguishing the various species.  Unfortunately, since azures usually hold there wings closed when they land, seeing the upper side can be a challenge unless you can net the insect.

In connection this project, I reviewed the identifications of the azure specimens collected during the CT Butterfly Atlas.  This enabled me to document the flight times for the azure species that occur in the state in the spring.  Information on flight times is included in the species accounts.

The following abbreviations are used in this article:

FW- Forewing

HW- Hindwing

YPM- Yale Peabody Museum, New Haven, CT

Species accounts

Spring Azure Celastrina ladon (Cramer)

Fig. 1, 2, 7

Upper side- The wings are purplish blue.  Under magnification, the scales are very close set and overlap each other, particularly on the FW.  The scales on the forewing are often very haphazardly arranged, although that is not easy to see in Fig. 7. 

Under side- The ground color is grayish brown.  Usually, the HW has a brown border and is often heavily spotted or blotched.   See Fig. 2.  However, there is at least one aberrant specimen collected during the Atlas project that is a uniform light brown without dark spots or splotches.   

Flight time- One brood; March 29 to May 31.

Comments- The Spring Azure can be distinguished from the other azure species by the combination of the grayish brown ground color on the underside of the HW and the purplish-blue color and the close set overlapping scales on the upper side of the FW.  Cherry Gall Azure and Summer Azure have a lighter ground color below and lack the overlapping scales on the upper side of the FW.  The upper side of the HW of Summer Azure is much whiter than the upper side of of the HW of  Spring Azure.  While the dark markings on the underside of Cherry Gall Azure can be quite similar to the dark markings on the underside of Spring Azure, on the Cherry Gall Azure, the rows of blue scales on the upper side of the FW are separated by distinct white lines. 

Spring Azure is the first species of azure to emerge in the spring.       

Summer Azure Celastrina neglecta (W. H. Edwards)

Fig. 3, 4, 8

Upper side- The FW is purplish blue; the HW is much whiter than the FW.  On the HW, the extensive white scales are arranged in distinct rays that reach the back edge of the HW, while the veins are blue.  This is very evident in Fig. 3.  Under magnification, the rows of scales on the FW are very close set but do not overlap each other.   

Under side- The ground color is a light gray with variable pale markings. 

Flight time- Multiple broods; May 15 to September 5.

Comments- Summer Azure can be distinguished from the Cherry Gall Azure by the white markings on the upper side of HW.  On Cherry Gall Azure, the white scales are arranged in a uniform light patch in the center of the HW and a blue margin is evident along the back edge of the HW. This is contrast to Summer Azure where the white patch extends to the edge of the HW and the blue is restricted to the veins.  In addition, the rows of white scales on the upper side of a Summer Azure FW are much closer set than they are on Cherry Gall Azure.  Summer Azure can be distinguished from the Spring Azure by the whitish HW above and the lighter ground color and much reduced markings on the underside. 

Summer Azure is the last species of azure to emerge in the spring and is the only species of azure flying during the summer.

Cherry Gall Azure Celastrina serotina Pavulaan & Wright

Fig. 5, 6, 9

Upper side- Wings above light purplish blue with a whitish patch in the center of the HW and a blue band along the back edge of the HW.  Under magnification, the rows of blue scales on the upper side of the FW are separated into rows that are separated by white lines.  See Fig. 9.   

Under side- The ground color is a light gray with variable dark markings. While many specimens are often quite pale underneath, see, for example Fig. 6, on some specimens, a brown marginal band is present on the back edge of the HW or a dark patch can present in the center of the HW. 

Flight time- One brood; April 25 to June 16.

Comments- Cherry Gall Azure can be distinguished from the Summer Azure by the white markings on the upper side of HW.  See the species account for Summer Azure.  Examples of Cherry Gall Azure with extensive brown markings on the underside of the HW can be confused with Spring Azure.  To distinguish individuals with extensive brown markings on the underside, you need to look at the scales on the upper side of the FW under magnification.  Compare Fig. 7 and Fig. 9. 

Cherry Gall Azures emerge after Spring Azures but before Summer Azures and often stay in close proximity to their larval food plant, Black Cherry (Prunus serotina).




Acknowledgements


I want to thank Harry Pavulaan for providing me with information on how to distinguish the various azure species that occur in the state.  Without the information provided by Harry, it would not have been possible to write this article.  I also want to thank Larry Gall at the Yale Peabody Museum who made the CT Butterfly Atlas voucher specimens and the Museum collection available for study.  Larry Gall also photographed the specimens and assembled the plates.

Literature cited


O’Donnell, J. E., Gall, L. F., Wagner, D. L. [ed.] 2007. The Connecticut Butterfly Atlas. State Geological and Natural History of Connecticut Bulletin No. 118.



Figures 1-9

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1-2, 7. Spring Azure Celastrina ladon (Cramer). West Rock Ridge St. Park, New Haven, L. Gall coll., April 19, 1980 (YPM ENT 732273); 3-4, 8. Summer Azure Celastrina neglecta (W. H. Edwards). Mansfield, H. Wilhelm coll., July 11, 1959 (YPM ENT 732274); 5-6, 9. Cherry Gall Azure Celastrina serotina Pavulaan & Wright. Beckley Bog, Norfolk, S. Hessel coll., May 31, 1958 (YPM ENT 732285).

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Connecticut Butterfly Association
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New Haven, CT 06532-0004