A Key to the Borers
of Apple
Douglas
G. Pfeiffer
Department of
Entomology
Virginia Tech
Blacksburg
The following is a key to borers in apple trees.
Characters have been compiled from several sources (given below).
Several
morphological terms should be reviewed. Caterpillars have six true,
jointed
legs on the thoracic segements, immediately behind the head. The
remaining,
abdominal segments have various arrangements of prolegs (fleshy
lobes used for grasping). These prolegs have small hooks, or crochets
(VCSU
image). These crochets may be arranged in a row of hooks of
equal
length (uniordinal), alternating long and short hooks (biordinal),
or
alternating
long, medium and short hooks (triordinal). The
crochets
may represent a circle, oval, or one or two rows of transverse bands.
- (1a) Prolegs present (Lepidoptera)
.............................
2
- (1b) Prolegs absent (Coleoptera)
.............................................
4
- (2a) Prolegs forming complete circle,
with
biordinal
to triordinal crochets ......................... American
plum borer, Euzophera semifuneralis
- (2b) Prolegs in two transverse bands,
forming
oval broken
at both ends (Sesiidae) ................ 3
- (3a) Head as broad as long
............................. Dogwood
borer, Synanthedon scitula
- (3b) Head distinctly broader than long
............ Apple
bark
borer, Synanthedon pyri
- (4a) Thoracic segments (just behind
head) widened,
disc-like
(Buprestidae)
......... Flatheaded
appletree
borer, Chrysobothris femorata
- (4b) Thorax no so wide (Cerambycidae)
....................................................
5
- (5a) About 1 inch when mature, tunnels
in
trunk .....................................
Roundheaded appletree borer, Saperda candida (NC
link; NY
and MI
photos)
- (5b) About 3 1/2 inches long when mature,
tunnels in
roots .............. Prionus
spp.
References
- MacKay, M. R. 1968. The North American
Aegeriidae
(Lepidoptera): A revision based on late-instar larvae. Mem. Entomol.
Soc.
Canada 58: 1-112.
- Peterson, A. 1962. Larvae of Insects. Pt. 1.
Lepidoptera
and Hymenoptera. Columbus OH.
- Stehr, F. W. 1987. Immature Insects. Vol. 1.
Kendall/Hunt,
Dubuque IA.
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