356 



YEARBOOK OF THE DEPARTMENT OF AGRICULTURE. 



THE HICKORY TWIG-GIRDLER. 



(Oncidcrcs cingnlata Say.) 



The work of the hickory twig-girdler, like that of the oak primer, 

 is confined to the twigs and branches, and is often quite injurious. 

 Only living trees are attacked. The list of host plants includes 

 hickory, basswood, poplar, dogwood, black 

 gum, elm, persimmon, and acacia. The range 

 of this species extends from the eastern United 

 States to Arkansas and Kansas. 



The larva is a footless white grub about half 

 an inch or more in length when mature. The 

 abdominal segments, except the last two, bear 

 minute granules, both above and below. The 

 adult (fig. 29, a) is a stout beetle. 12 to 14 mm. 

 in length, dark gray to reddish brown in color. 

 The flight of the adults and the deposition of 

 eggs usually occur in August or September. 

 The adult female punctures the branch or twig 

 and deposits an egg in each puncture. She 

 then gnaws off the bark and outer wood at a 

 point on the branch below where the eggs are 

 laid, completely circling the limb and causing 

 that portion of it beyond the girdle to die (fig. 

 29). The eggs hatch and the larva?, after min- 

 ing in the inner bark (fig. 29, 6), bore to the 

 center of the branch, where pupation takes 

 place in the larval mine, little if any protective 

 device in the way of a pupal chamber being 

 made. Probably most of the infested twigs 

 and branches fall to the ground before the 

 larva? complete their development, though some 

 do nor. It has been found that in the infested 

 branches which do not fall the larvae seldom 

 complete their development to the adult stage 

 unless the branches are in a shaded position. 

 Likewise, few adults are produced from 

 branches which are freely exposed to the sun after falling. This 

 insect reaches its best development in shaded twigs or branches, or 

 those partially covered by leaves or vegetation. In North Carolina 

 the larvae begin to pupate about August 1 of the year following that 

 in which the eggs were laid, most of the adults probably emerging 

 in September. The winter is therefore passed in the larval state. 



FIG. 29 Work of the 

 hickory twig - girdler 

 (Oncideres cingulata) . 

 Acacia branch showing 

 girdle, and larval mines 

 in bark and outer wood. 

 Insect natural size. 

 (Original.) 



