As springtime temperatures wax and wane, insect life begins to increase and we
are treated to the gradual re-awakening of an insect horde. Two of my favorite
groups of insects, the dragonflies (odonates or "odes" for short) and the
butterflies (lepidopterans or "leps" for short) provide a lot of excitement
during this early time of year. It is very rewarding to see old friends from
these insect groups reappear and colonize their habitats.
One of the most easily recognizable of the dragonflies this time of year is the
Carolina saddlebags. The large dark reddish patches at the bases of the hind
wings and the red abdomen of the male are very distinctive. The purpose of
these markings is not obvious and they would seem to make the insect a target
for predators. But this is a very agile flyer which is not easy to catch. A
nearby dragonfly, the lancet clubtail, is very drab and less noticeable. In
fact this well camouflaged species is often found perched on the ground or low
vegetation. These are both very aggressive predators on insects as adults and
as aquatic nymphs.
One of the most beautiful butterflies is the red admiral. It is migratory and
found also in Africa, Eurasia and Central America. The purpose of the bright
colors of the inside of the wings is not clear since the caterpillars feed on
nettles and are not likely to be toxic to predators. Since the butterfly is an
erratic and rapid flyer, perhaps these are simply flash colors involved in
species recognition.
A common butterfly in May is the light blue azure, which is one of several
members of the spring/summer azure complex. The difficulty of separating these
azures reminds us that evolution continues to occur even now and the
distinctions we try to make between individual species are not always clear in
the real world. Another confusing group is the sulphurs. The individual shown
is probably a white morph orange sulphur, but the distinction between it and
the clouded can be difficult in the field. To add additional confusion a third
identification challenge was flying in the same area, the duskywing skipper.
This appears to be a Juvenal's duskywing that is nectaring on a geranium
flower. They are as dark and murky in color as the typical butterflies are
bright.
A challenge in butterfly identification that I deal with daily is a group of
similarly colored large butterflies I call the "black and blues." They are
involved in a mimicry complex based on resemblance to the toxic pipevine
swallowtail and can be difficult to separate. One commonly seen member is the
female black tiger swallowtail; all males are the yellow morph as are many
females. Proportionately more black females are seen to the south where the
pipevine swallowtail is found. The "tails" of the swallowtail are likely false
heads to divert the strike of predatory birds away from the vulnerable head
region. Although the mimicry is assumed to be Batesian, in which the toxic
pipevine is mimicked by the tasty black morph tiger swallowtail, tiger
caterpillars do feed on black cherry trees which contain compounds of cyanide.
Similarly another mimic, the spicebush swallowtail feeds as a caterpillar on
spicebush and sassafras, both of which contain toxic and potentially toxic
chemicals. So perhaps some day when more information become available, the
relationship among these similarly colored butterflies may be found to be more
complex than assumed now. This is what happened when the previously assumed
tasty viceroy was found to be toxic due to its diet of willow. Thus it is a
Muellerian and not a Batesian mimic of the monarch. Watch for some other
members of the fascinating "black and blues," such as the red spotted purple
and the female Diana fritillary butterflies.
I find it both exciting and frustrating that it can be difficult to identify
some of the intriguing insects that we encounter daily. It should teach us that
nature is complex and that our systems of categorizing species do not fully
represent the range of variation that actually occurs, and that evolutionary
change is continuing to occur.
Bill Dunson
Galax, VA and Englewood, FL
http://lemonbayconservancy.org/news-blog/nature-notes-by-bill-dunson/
http://pieenvironmental.blogspot.com/
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Saddlebags carolina VA farm pond eight 5.8.15 Bill Dunson IMG_6576 aa.jpg
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DragonflyLancet clubtail Hale Llake VA 5.11.15 Bill Dunson IMG_6628 aa.jpg
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Red admiral on fringed phacelia Elk Garden 5.9.15 Bill Dunson IMG_6584 aa.jpg
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Azure spring summer complex BRP 5.12.15 Bill Dunson IMG_6657 aa.jpg
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Orange sulphur white morph female Homestead Rd 5.18.15 Bill Dunson IMG_6708 aa.jpg
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Duskywing Juvenals male on geranium Homestead Rd 5.18.15 Bill Dunson IMG_6720 aa.jpg
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Black tiger swallowtail female in VA yard on lilac 5.4.15 Bill Dunson IMG_6444 aa.jpg
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Spicebush swalowtail male Homestead Rd 5.18.15 Bill Dunson IMG_6714 aa.jpg
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Pipevine. swallowtail in yard.jpg
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