71 
are more numerous, and on the average smaller than in the normal 
internode. The ‘also ditter somewhat in structure, as will be 
described below. Thus the presence of the insect, in the successive 
stages of larva and pupa, causes considerable modifications in the 
structure and development of the internode, the most striking 
feature being the excessive intercalary growth of the gall. The 
latter may attain a length of more than thirty times that of 
the normal internode. 
mong the material examined there were a few galls in an early 
stage, It is probable that they would have developed into mature 
structures like those described above, but with the difference that 
the leaves immediately sheathing the base of the gall were not 
scale-like, but ha eveloped a lamina. = ‘This “difference is 
presumably due to the bud having been attacked at a slightly 
different stage. A branch with one of these young galls is shown 
in Fig. 3. “This specimen is only distinguished from a normal 
branch by the slight swelling near the base. On removing the 
leaves, the swollen internode is seen oe a by the youngest 
leaf-rudiment (Fig. 4). he insect, which is in the larval stage, 
nearly fills the Sntepua) cavity of the gall, as is seen in the enlarged 
longitudinal section (Fig. 5). 
Specimens of this larva, and of the pupal skins from mature galls, 
were sent to Prof. J. J. Kieffer, who kindly examined them, and 
wrote the following yin dee for publication. 
“ Oligotrophus ischaemi, sp. nov.—Larve blanche, longue de 
2 mm., lisse; verrues esha alge trés fines, situées sur la partie 
ventrale des deux derniers segments thoraciques et de tous les 
segments abdominaux ; toutes les papilles sont snag sauf les huit 
terminales, qui sont pourvues d’une soie trés courte et peu distincte; 
papilles pleurales et sternales assez grandes, les Platieales internes 
isposces par groupes de trois; papilles ventrales antérieures et 
postérieures petiies et peu apparentes. egment anal arrondi, 
légérement échancré au milieu; sa partie dorsale porte, 4 sa base, 
quelques pene ip éparses, et dans sa moiti¢ postérieure, des 
téguments s 
me sealer Sean grande, sessile, aussi longue que large, munie en 
avant, de deux dents triangulaires qui sont deux fois aussi longues 
que larges } a leur base, et séparées l’une de l’autre par une incision 
largement arquée. ymphe a peau hyaline ; spinules dorsales 
fortes, jaunes, disposes en’ 3 & 4 rangées ; stigmates thoraciques 
3 4 4 fois aussi longs que gros, cylindriques et épais. 
With regard to the generic determination Prof. Kieffer adds :— 
“Le genre Olgotrophus est voisin de Mayetiola; si la pupe est 
une coque brune, l’insecte serait un Mayetiola, quoique tous les 
Mayetiola connus aient la peau couverte de téguments et non lisse, 
a Pétat larvaire 
Among the mature galls one exceptional case was met with 
Fig. 6). The gall was of the usual type except that there were 
three small holes (Fig. 6a), instead of the single rather larger one, 
and also the gall was not empty, but contained, as Prof. Kieffer 
determined, a distended skin (of the gall-insect) inhabited by 
We 6G of a The gall insect ee to the genus Platygaster 
(Fig. €, 2) -insect had clearly been killed by the 
15747 a aa 
