Life Cycle: Mating


One night I watched a moth land in some foliage of a Pokeweed plant in a flower border about 20 ft. from my mercury vapor lamp. Using my headlamp I found it clinging to the underside of a leaf about 2 ft. above the ground. I decided to get my camera, set it in flash mode, and was trying to decide on the best angle for photographs when I notice movement near the ground beneath the group of tall plants. It was a moth fluttering back and forth as if it couldn't decide which way it wanted to go. I didn't realize that I was observing a female "calling" a male by releasing pheromone "sex attractant." When the fluttering moth got a good whiff of the pheromone he beelined it to land right beside the female. In what seemed like a blink-of-the-eye, no more than 2-3 seconds, I saw a brief movement of abdomens and then the male fell backward off the leaf. He didn't fall far, however, but swung like a pendulum a few time until coming rigidly to rest as seen in the photo at right, below. They didn't seem to mind my being a few feet away or the sounds of the camera or the flash. They remained in this position for at least 30 minutes, but were gone a couple of hours later when I thought to look for them again.

Carmenta ithacae [tentative]
Tam Stuart
Carmenta ithacae [tentative]
Tam Stuart
Curve-toothed Geometer
Robert Patterson
Curve-toothed Geometer
Machele White
 

Tam Stuart's photos of the Clearwing Moths reveal the frequent disparity in size between males (usually smaller) and females. In the top center photo the pair have just made genital contact. They then flew in tandem, the female leading and in control, to a nearby leaf where the female is in the typical "superior" position (left, above). A short movie requiring Macromedia Flash Player shows a male's approach to a female, genital connection, and fall-away to final position of Grape-root Borer Moths, Vitacea polistiformis, at John Meyer's ENT425 page on Chemical Communication. In this case there seems to have been a few seconds of excited stimulatory behavior on the part of the male.

  Life Cycle: Diapause, Aestivation and Overwintering


Diapause, Aestivation and Overwintering/Hibernation all refer to periods of inactivity. Aestivation or Overwintering refer to inactive periods in the adult stage of the moth life cycle. On the other hand, diapause is a halt or pause somewhere in the development process of the egg, larva or pupa. The pause can be relatively short or long. In the case of the Eastern Tent Caterpillar Moth, Malacosoma americanum, the eggs laid in the spring develop to the point where the first instar larvae are about ready to hatch. The larvae then go into diapause (still within the egg) for a period of 9.5-10.5 months, waiting for their primary food, leaves of forest trees, to leaf out. The data for the chart shown below is for Alabama but, except for the beginning and ending dates for each life stage, would look just about the same for more northerly areas. The lengths of each stage would be similar. Note that this species spends less than 10% of the life cycle in the adult stage.

Nolie Schneider Eastern Tent Caterpillar Life Cycle
Lacy L. Hyche, Auburn Univ., www.forestryimages.org
Robert Patterson


Illustrating diapause in the larval stage is difficult. The caterpillar will simply be inactive (although often able to move if touched or disturbed) and might appear to be somewhat shrunken or shriveled up. Adult moths may aestivate during a period of heat or cold and spend a considerable period of time hidden in leaf litter, under the bark of a tree or in a tree cavity (or in modern analogues such as sheds or under siding). We wouldn't expect to see any real difference between aestivating moths and ones active at a light sheet except that they would be at some location where they can be inactive and not exposed to harsh climate. Here are some moths known to take shelter in caves. Two of them are covered by droplets of moisture due to the ambient air having reached the dew point. See the paper Hop Vine Moths, Hypena humuli in a Wisconsin Cave.

Sean McCann -- Tissue Moth
Triphosa haesitata
Bill Johnson -- Hop Vine Moth
Hypena humuli
Bill Johnson -- Herald Moth
Scoliopterix libatrix







MothTalk/MothTalk019.htm -- 01/15/2007