Key to Most Common Caterpillars Found on Flowers and Foliage Plants
1. Small, slender caterpillar mining in the leaves or folding the tips of the leaves of azaleas (Fig. 62)........Azalea leafminer.
1'. Not mining the leaves or folding the tips of leaves of Azalea ......... 2
2. Young larvae mine in leaves and later burrow into the stem, petioles, flowers, or seed pods of geranium and snapdragon (Fig. 63) ...... Plume moth caterpillars
2'. Not mining in leaves and burrowing into the stem, petioles, flowers, or seed pods of geranium ........ 3
3. Variously spotted and marked caterpillars feeding on the foliage of ferns (Fig. 64) ....... Florida fern caterpillar.
3'. Not feeding on ferns .......4
4. Whitish caterpillar feeding on and within the rhizomes of iris (Fig. 65).......Iris borer
4'. Not feeding on or within the rhizomes of iris ..... 5
5. Relatively slender caterpillar (Fig. 66) feeding only on plants in the mustard family (Cruciferae), at least 4 pairs of prolegs, prolegs relatively long, one row of crochets around the end of each proleg, usually feeds under leaves, riddling the foliage; when disturbed often hangs down by a silk thread ...... Diamondback moth.
6. Boring into the stalks of garden mums and shasta daisies and other stems of flowering crops (Fig. 67)...... European corn borer.
6'. Not boring into the stalks of garden mums, shasta daisies, and other stems .......7
7. Tying or rolling the leaves of the host plant with silk strands ...... 8
7.' Not tying or rolling the leaves of the host plant with silk strands ......11
8. Tying or rolling the leaves of canna .......... 9
8.' Not tying or rolling the leaves of canna ........ 10
9. Caterpillar slender, up to 23 mm long with yellowish head (Fig. 68)... Lesser canna leafroller.
9'. Caterpillar relatively robust, green, somewhat transparent, brown head on a distinct neck ......Larger canna leafroller.
10. Shield on first thoracic segment only slightly darker than rest of skin but with a distinct dark spot on either side; there are two prespiracular setae on the first thoracic segment; caterpillar green and sometimes with a darker green stripe along the back and a paler green stripe along either side (Fig. 69A); prolegs with crochets in arranged in circles with three rows on the inside but one row on the outside (Fig. 69B); no anal fork........ Greenhouse leaftier.
10'. Not as above; three prespiracular setae on first throacic segment, anal fork or comb present on last abdominal segment (Fig. 70); crochets on last pair of prolegs not in a complete circle ..... Choristoneura and Platynota leafrollers.
11. Caterpillar with only two pairs of prolegs (plus three pairs of legs on the thorax, Fig. 71), loops as it travels on plant; feeds on leaves and flowers....... Cabbage looper.
11.' Caterpillar with five pairs of prolegs on abdomen (plus three pairs of legs on thorax), does not loop as it travels along; feeds on various parts ...... 12
12. First and second instars are pale green with dark heads; older caterpillars are green to almost black with stripes along each side; always have a black spot on the side above the second pair of legs (counting from the head, Fig.72) Beet armyworm.
12'. Caterpillar variously colored but never with a black spot on the side above the second pair of legs (counting from the head)....... 13
13. Primarily a pest of buds and flowers, caterpillar remains on plant during the day (Fig. 73) ..... Corn earworm.
13.' Primarily a pest of foliage; caterpillars (especially older caterpillars) tend to hide in the soil or potting mix during the day (Fig. 74 A to C)....... Cutworms.