Synanthedon acerni

Maple Callus Borer
Synanthedon acerni


POHL: 64-0095
MONA: 2554
GenBank: 689287

Head: Dark orange, including back of head and nose cone (palpi). Inner eye margin white.
Antenna: Long, entirely brown-black. Base (scape) orange. Male antennae have very fine, barely visible short hairs (pectinate).
Thorax: Deep orange; fading to yellowish-brown, or almost bald (black) on older individuals. Faint orange stripe down each side, widening into tufts by wing base; may be absent in older individuals. Underside yellow.
Wings: Both front and hind wings are transparent, so the dark mark and border of hindwing may be visible through the front wing.
Forewing margins black,  streaked with yellow on outer (costal) margin. Wide black bar at 2/3 wing length (discal cell). Wing tip area yellow with narrow black bar before the yellow, fading out at center, but may appear solid, thicker and darker if the border of the hindwing is showing through. A small black spot on outer (costal) border at end of this narrow bar. Below the bar wing is entirely yellow with black veins. Fringe short, grayish-black.
Hindwing margins narrow, black; outer (costal) margin streaked with yellow. Mid wing has a wide black bar extending across 2 veins; may be visible through to front wing. Fringe grayish-black. Male hind wing has some faint yellow at tip.
Legs: For the most part yellowish, streaked with brown. Front leg usually more orangish. All shins have darker tips. Feet very long and thin, faintly streaked or ringed with brown.
Abdomen: Black, lower half or less of each segment, except 3rd  usually absent, has yellowish scaling, wider at side edges. On older individuals reduced to only a yellowish line. Underside yellowish-brown with black patch at sides of 2nd segment. Female abdomen wider, tip with a bright orange tuft. Male tuft has base half black, rest orange, underside of tuft yellow.

Similar Species: Red Maple Borer Synanthedon acerrubri has entirely black area at wing tip, no yellow and the antennae have a white streak before tips.

Size: 8 to 10 mm. long. Wingspan 18 to 22 mm.

Habitat: Deciduous forests.

Food: Silver Maple Acer dasycarpum, Red Maple Acer rubrum, Sugar Maple Acer saccharinum, and Mountain Ash Pyrus americana. Attacks only trees weakened from previous injuries.

Flight Time: May to August

Life Cycle: The female lays one egg in each wound on trunks, seldom in branches of maple trees, often using the same wound each year; female lay eggs continually during the summer. The larvae feed on tree sap in tunnels, over-winter, resume feeding in the spring and move back to entrance hole to pupate. The pupa, capable of movement, works its way to the surface. The moth emerges, usually in the early morning, leaving the pupa half popped out of the entrance hole.
Larvae 12 to 19 mm. Pale yellowish-brown, flattened; head small, rounded and more yellowish, black between antennae. Abdomen tip with tubercle at each side. Legs reddish. According to literature, the male is the only Clearwing Borer attracted to lights, but a few others, including Synanthedon tipuliformis males have been taken at moth lights.

Comments: Common. Essex County – Point Pelee National Park insect list. Kent County – Rondeau Provincial Park insect list.
The destruction of native Maples by S. acerni caused municipalities to use the non-native Norway Maple Acer platanoides which was resistant to infestation of many of our native insects. Infestations of native Maples were rampant, causing death in municipal areas, but rare in forests. Kellicott (1880’s) thought this was due to a lack of woodpecker activity in towns and cities.

For information on synonyms, references and type specimens see next page