The Ohio ^ACaturalist, 



PUBLISHED BY 



The Biological Club of the Ohio State University, 

 Volume III, MAY, 1903. No. 7. 



TABLE OF CONTENTS 



Cook— Galls and Insects Producing Them 419 



Derby— Meeting of the Wheatou Club 437 



Griggs— Meeting of the Biological Club 438 



IjANuacre— Notice to Subscribers 438 



GALLS AND INSECTS PRODUCING THEM. 



Melville Thurston Cook. 



Part III. Laterai, Bud Galls. 



In Part II of this series of papers I gave a discussion of apical 

 bud galls. The lateral bud galls differ from the apical only in 

 point of location ; therefore, this (Part III) may be considered a 

 continuation of Part II. There is, however, considerable differ- 

 ence in the galls dependent upon the order and genus to which 

 the insect belongs and to the part of the plant which is attacked 

 by the enemy. These differences may be summed up briefly as 

 follows : 



( 1 ) Affection of the tip of the stem causing it to remain in its 

 incipient condition and the leaves to remain aborted, instead of 

 lengthening. This is well illustrated by the apical bud galls of 

 Cecidoniyia so/idagiuis Lw. on Solidago ; Cecidoniyia sa/his strobi- 

 loidcs O. S. on Salix ; and Callirhytis clavida Fitch on Quercus 

 alba. (Part II, Figs. 31, 32, 33.) In these cases we have two 

 orders of insects represented but producing similar galls : this, as 

 previously explained, is no doubt due to the fact that the insects 

 affect corresponding parts of the host plant. 



(2) Affection of the tip of the bud causing it to remain short 

 but to become large and globular. This is well illustrated by 

 Holcaspis globulus Fitch (Fig. 34, a, b, c) By collecting speci- 

 mens of this gall in April or early part of May it is easy to 

 demonstrate that the gall is in reality an enlargement of the stem 

 part of the bud. The insect evidently deposits the ^^'g in the 

 apical part of the incipient stem. This causes the stem to enlarge, 

 forming a globular body, but to remain so short as to form a 

 sessile gall on the main stem. The bud scales are at first very 

 prominent but gradually shrivel up and are lost, leaving a naked, 



