GALLS CAUSED BY GALL- WASPS 27 



representing nearly all the orders, have been obtained from 

 a single gall ! 



The cynipidous galls may be conveniently considered 

 under two headings. 



I. GALLS ON PLANTS OTHER THAN OAK 



The causers of these belong to five genera — Aulacidea, 

 Aulax, Diastrophus, and Rhodites. 



Aulacidea hieracna.tta.cks the stem, and root of the Common 

 Hawkweed, Yellow Toadflax, and Couch-grass ; the larvae 

 give rise to longitudinal or rounded swellings. In the last 

 named the distortion is usually slight. Several larvae occupy 

 a cell. Galls caused by certain species of Aulax are very 

 familiar objects. Three of them are shown in our plates. 



The larvae of Aulax hypockaeridis give rise to elongated and 

 fusiform (rarely rounded) swellings on the stem of the Long- 

 rooted Cat's-ear (Plate XXIX., Fig. i). The petioles are 

 sometimes attacked, and not infrequently the whole plant 

 is deformed. The galled part is yellowish-green or brown 

 at maturity. The gall is plurilocular ; each cell contains a 

 yellowish-white larva. Fig. 3 depicts a section, natural size. 

 The larvae pupate in the gall, and the wasps appear in 

 spring. Plate XXIX., Fig. 4, shows an imago, magnified. 



Equally common galls arise on the leaves and stems 

 of the Ground Ivy (Plate XXIX., Fig. 5) when attacked by 

 Aulax glechomae. They vary in size from a pea to a large 

 marble, are yellowish-green at first, becoming suffused with 

 red or purple at maturity, and are covered with long white 

 hairs. These galls are usually solitary ; sometimes two or 

 three coalesce; a section of such is shown at Fig. 7. The 

 larva (Fig. 8) pupates in the gall, the imago (Fig. 9) 

 appearing the following April. In the growing state the 

 gall is soft and sappy ; at maturity the interior is dry and 

 fibrous, the larva being encysted in a remarkably hard 

 inner gall. The larvae are attacked by several parasites. 

 R6aumur * remarked that these galls were eaten by the 

 * "M^m.," iu.,p. 416. 



