1914] A Study of Dryophanta Erinacet. 19 
The Malpighian Vessels of Gall-Producing Tenthredinide. 
The larva of Nematus pomum (Walsh) which causes the 
willow-apple gall was secured. Longitudinal sections through 
the larva show cylindrical tubules arising at the union of the 
mid and hind-gut, and extending caudad, (Fig. 66, Pl. IX). A 
longitudinal section of the tubule is shown in Fig. 65, Pl. IX. 
The cells are numerous, small, and regular, the nuclei being 
symmetrical, and densely packed with chromatin. We have 
no evidence here of great activity, nor does the larva secrete 
any fluid when placed on a foreign substance. 
Now it is known that the Tenthredinide do not produce 
galls in the same manner as the Cynipide, but the stimulus is 
given at the time of oviposition. Adler says “I have carefully 
observed Nematus vallisnierii. The fly cuts into the tender 
leaves of the end shoot of Salix amygdalina, and inserts her eggs 
in the wound, frequently placing several in one leaf. At the 
same time some glandular secretion from the insect flows into 
the wounded leaf. A few hours after this injury, the leaf 
surface presents an altered appearance, and new cell-formation 
begins, freely leading to the thickening of the surrounding leaf 
surface. After the elapse of about fourteen days the green and 
red, bean-shaped gall is fully grown. If it is now opened the 
egg will be seen lying in the cavity. Three weeks elapse before 
the larva emerges from the egg.”’ 
Thus it is evident that the Malpighian vessels of the Ten- 
thredinid larva are not factors in gall production. 
The Malpighian Vessels of the Gall-Producing Diptera. 
The larva of Trypeta solidaginis, from the globular gall on 
the goldenrod, shows Malpighian vessels consisting of small, 
round cells containing spherical nuclei, (Fig. 68, Pl. IX). The 
cells show no evidence of exceptional activity, nor have we any 
reason to believe that the Malpighian tubules are here factors 
in gall formation. 
The larva of Cecidomyia strobtloides, which causes the pine- 
cone willow gall, likewise shows Malpighian vessels of a normal 
type. The cells are small, very regular, and do not indicate 
any unusual state of activity, (Fig. 69, Pl. IX). 
