INSECTS AFFECTING PARK AND WOODLAND TREES 



639 



Willow cone gall 

 Rhabdophaga slrohiloiiics Walsh 

 A peculiar conelike deformity on the tips of willow sluiots i;- 



liic to tlic work of this 



These interesting galls are rather common objects about All)aiiy, ami 

 the insect presumably has a wide distribution in the United States, though 

 specific records of its occurrence are not abundant. 



Description The gall, a tapering, conelike, terniinal growth, is 

 obviously a mass of aborted leaves, one overlapping the other much as the 

 scales of a pine cone. This deformity was figured by Glover in 1874, in 

 addition to the description and illustrations given by Walsh, who also 

 figured the adult fly without describing it. 



Life history. The parent insects, according to Walsh, appear in April 

 or early May, and the gall commences its growth shortly after and attains 

 full size by the middle of June. In its early stages it is spherical and 

 enveloped in a dense mass of foliage, which gradually falls off toward 

 autumn, and by November the twig 

 on which it occurs, if small, is killed 

 at the tip. At this time the larva is 

 in the heart of the gall inclosed in a 

 delicate membranous cocoon, where 

 it remains till the following spring, 

 when it transforms to the pupa and 

 shortly after the fiy escapes. 



Witch-hazel cone gall 

 Hormapliis hanianiclidis Fitch 

 Conical, green or reddish galls occur 

 in considerable numbers on the upper sur- 

 face of witch-hazel leaves. 



ThoUSfh this remarkable plant f'ei?' Hormaphis hamamelidisia-galls, natunl si^e 



_ /'-section of gall, much enlarged. (After Pergande, U. S. 



louse was briefly described by Dr oep't akHc. div. Em. xech.ser. 9, iqoo 



Asa Fitch in 1851, very little was known concerning the species till it was 



