150 Memoirs of the Indian Museum. [ Vor. VI, 
it differs in several important respects both in the apterous and the alate form. 
The colour, size, number of antennal joints of the apterous female and the sensoria 
and wings of the alate form are dissimilar in the two. 
The Pemphigus on Cynodon is apterous throughout winter and spring, forming 
winged individuals only in late April or early May. Their further history is obscure. 
They were never observed on grass from May to October, nor were they ever noticed 
on Pistacia. If in spite of these differences any connection between these two 
species is established later on, a complete life-cycle might be expected to be some- 
what like this :— | 
The eggs hatch into stem-mothers in March and found new colonies within the 
galls containing apterous females till October; in November the aphids leave the 
galls as winged viviparous females. From November to April or May of the following 
year the generations are all wingless; in May they would go to Pistacia as alate 
females but viviparous again, the progeny of these would, at some time from May to 
November or December, develop the sexual individuals that would lay eggs in the 
buds. ‘These wintering over must hatch again in March. ‘Thus the life-cycle would 
extend over at least two years, but this remains to be established. 
Formation of the galls.-—The leaves of Pistacia integerrima are compound ones as- 
shown in the accompanying reduced drawing (pl. xiii). Each possesses a long pedun- 
cle, having five or six pairs of nearly sessile leaflets. Almost invariably it is the top- 
most leaf of a branch on which the galls develop, and therefore are always terminal. 
At a time when the leaflets are very young and the peduncles hardly elongated at all, 
the stem-mothers hatch from the eggs and fix themselves near the bases of the leaflets on 
their upper surface. In a manner very similar to what is seen in some Psyllids, they 
make a depression which bulges as a conical projection ventrally. This pit, by con- 
stant irritation, grows larger and its top slowly closes up, so that there is now a 
closed finger-like process on the underside of the leaflet, in which the stem-mother 
is enclosed. These are the future galls, and there may be as many as six or eight on 
one compound leaf: ordinarily their number is limited from one to four, the common- 
est number being two as shown in the figures. The leaflet on which the gall develops 
soon atrophies; other leaflets may grow even to their normal size, but generally 
remain stunted. : 
The first effect of gall-formation on a leaf is the arrested growth in length of its 
peduncle which usually becomes thickened and curved downwards, so that the leaflets 
and the growing galls are situated quite close to each other. If the leaflets drop off 
early the galls become terminal. 
Growth.—The galls grow very slowly at first, but in about two months’ time they 
attain a length of two or three inches; in breadth they vary from + to + of an inch. 
In the shade the colour remains green, but the portions that are exposed to the sun 
turn partly pinkish. The inside is perfectly smooth, pink, and dusted with white 
powder from the backs of the insects. This powder when abundant collects in the 
lower end of the gall, and protects the insects from becoming wet with their own 
liquid excreta, which trickles in white drops, 
