236 NORTH AMERICAN INSECTS. 



wasps ; viz., that of the Cynips oneratus (Fig. G4), and 

 seminator (Fig. 65), both found on the white oak. 



At almost any season of the year, by examining the 

 small twigs of the white oak, we may find around them 

 clusters of oak-balls, of the size of a small marble, which 

 are as hard as wood. These hard excrescences are the re- 

 sults of the punctures made in the tender twigs by the 

 Cynips oneratus, who at the same time deposits its eggs in 

 them. The swelling of these punctures is caused by the 

 gradual enlargement of the egg, and also by the continual 

 irritation of the little maggot, who is thus furnished with 

 food and a secure dwelling until it is ready to perforate 

 the oak-ball and come forth as a perfect four-winged wasp, 

 which metamorphosis usually takes place in June or July. 

 This little wasp is very small, being only about the sixth 

 of an inch long. 



Oak-balls of this kind are found every where in North 

 America, and they might possibly be substituted for those 

 we receive from the Levant, and which constitute such a 

 valuable dye-stuff. They have never been used as such to 

 our knowledge ; but the suggestion is well worth the atten- 

 tion of chemists and dyers ; for, if experiment should prove 

 them as valuable as the foreign oak-balls, a vast amount 



Figure 65. 



The Sower Gall-wasp. 



