ne Ohio ^]\Caturalist, 



PUBLISHED BY 



The Biological Club of the Ohio State Uni'versity, 

 Volume IV. APRIL, 1904. No. 6. 



TABLE OF CONTENTS 



Cook— Galls and Insects Producing Them 115 



Cook— Galls and Insects Producing Them. Appi-ndix 1 140 



News and Notes 1 ■IS 



GALLS AND INSECTS PRODUCING THEM.^ 



Melville Thurston Cook. 

 Part VI. Flower and Fruit Galls. 



Galls affecting flowers and fruits are not so abundant as those 

 affecting leaves, but in many cases the insect which produces 

 flower or fruit galls also produces leaf galls. No sharp line of 

 distinction can be drawn between flower and fruit galls, since the 

 gall ma}' form and mature without indication of fruit or may 

 form in the flower and mature as the fruit develops. Thus far I 

 have collected five species of flower and fruit galls representing 

 three orders of insects. 



I. GALLS OF THE ACARINA. 



Phytoptus sp. — on Euphorbia corallata L. (Figures 70 ; 71a, 

 b ; 72a, b). This mite produces galls on both leaf and flower. 

 The structure of the gall is the same in both cases and is identi- 

 cal with Phytoptus galls, previously described in Part I, (Figures 

 811). All my specimens of this gall were well advanced. The 

 structure of the leaf of E. corallata ( Fig. 70) is typical. When 

 attacked by the Phytoptus the leaf becomes very much modified 

 by thickenings, ridges and convolutions (Figures 71a, b). The 

 palisade cells divide so that it is impossible to distinguish them 

 from the mesophyll, and the intercellular spaces are obliterated as 

 the result of the rapid cell division. The new cells are small and 

 very rich in protoplasm, but gradually become filled with tannin 

 as the gall approaches maturit)-. The tannin first forms in the 

 outer and most exposed cells of the gall while the inner laj'ers of 

 cells retain their protoplasm very late. The Phj'toptus restricts 

 its attacks to these inner and more protected parts. From a study 

 of these galls it is apparent that the Phytoptus is not working on 



* Contributions from the Department of Zoology and Entomology, Ohio State Univer- 

 sity, under the direction of Prof. Herbert Osborn, No. 17. 



