ENGLISH: ILLINOIS TREES: THEIR INSECT ENEMIES 47 



neling under the bark. Often, trees are girdled by the white, leg- 

 less, slender grubs with big flat heads. Feeding mainly in the 

 sapwood at first, each grub mines deeper as it becomes larger 

 and when grown it makes enough room at the end of a tunnel to 

 spend the winter. Pupation and transformation take place in the 

 early spring. At this time, an adult emerges through the tunnel 

 made by a borer. The life cycle of the flatheaded apple tree borer 

 is completed in a year. 



Control Measure U (end of circular) . 



Aphids. — Two species of aphids are pests of maples. They 

 suck sap from the under sides of maple leaves and secrete enough 

 honeydew, at times, to wet the sidewalks and streets under the 

 trees. The Norway-maple aphid, Periphyllus lyropictus (Kess.), 

 is a greenish insect that feeds along the veins on the under sides 

 of the leaves of Norway maple and hard maple. The painted 

 maple aphid, Drepanaphis acerifoliae (Thos.), is gray or black 

 in the winged form and yellow in the wingless form. It is more 

 common on soft maple than on other maples. 



Control Measure 3 (end of circular) if damage is apparent 

 and if the nuisance caused by the aphids is insufferable. Aphids 

 usually do not cause enough damage to large trees to justify the 

 expense of spraying. 



Pigeon Tremex, Tremex columba (L.). — Associated with 

 diseased and dying maples and many other kinds of trees, the 

 pigeon tremex may be erroneously blamed as a serious tree pest. 

 Each almost 2 inches long and with a reddish head and thorax, 

 the adults are wasplike sawflies that bore holes in the trunk of a 

 tree ; there the female deposits eggs which hatch into grubs that 

 live in the infested tree until development and transformation 

 are completed. 



Control. A slender parasitic wasp belonging to the great 

 family of parasites, the Ichneumonidae, probably does more to 

 control the pigeon tremex than could be done with all sorts of in- 

 secticides. With her ovipositor, a long threadlike appendage at 

 the end of her abdomen, the female of this wasp, with uncanny 

 precision, drills into a tremex tunnel and deposits an egg which 

 produces a larva that attaches itself to the tremex grub and 

 kills it. 



No insecticide treatment is recommended for the pigeon 

 tremex. Trees infested by the tremex probably should be cut 

 down and removed because they are dying from other causes. 



