232 Memovrs of the Indian Museum. [Vor. VI, 
like rain, frost, etc., because after these conditions have disappeared there still 
remain a large percentage which do not hatch. Some facts were observed while 
studying this species that seem to offer an explanation. For conclusive proof of 
course a special set of experiments with a definite aim would have to be carried out. 
One or two insects to each branch were isolated-on several branches of a Peganum — 
plant in the laboratory in October 1913. and the twigs were enclosed in loose muslin 
bags, with the idea of watching their growth and collecting sexual forms. In the 
bags males were formed some days earlier than the females, the latter after the 
middle of November. Most of the males died soon after this, while the oviparous 
females remained wandering about, each carrying its large egg. By the end of Decem- 
ber all the females had laid their eggs and only some viviparous females with young and 
pupae were left. None of the eggs hatched, probably because none were fertilised. 
It is a somewhat parallel case with what is well known in Protozoa, like Para- 
maecium. From the original ‘‘stem-mother’’ insect that hatches from the egg, we 
get in succession a large number of parthenogenetic generations, ending in the last one 
by the formation of true sexual individuals. The descendants of this common ances- 
tor seem very much averse to mating among themselves. It would therefore appear 
that unless other males are introduced from a different stock an isolated colony how- 
ever large its numbers would die a natural death, without being able to lay fertilised 
eggs to carry on the species into the next season. For this reason it very often 
happens that from single plants in the field as well as in the laboratory we seldom 
secure eggs that hatch, the clustering thousands being the descendants of only a single 
Aphid. Davis, Gillette and others have also noted that most of the eggs gathered 
in the insectaries shrivel up, while some of those laid and left unprotected outside 
do hatch. These in all likelihood must have been cross fecundated and fertile. 
Peganum harmala, vernacular ‘‘ Harmal’’ or ‘‘ Aspand,’’ is a bushy Xerophytic 
herb with white flowers and much-divided leaves. By some it is placed among the 
Rutaceae as an aberrant genus of that order, while others consider it to belong more 
properly to Zygophyllaceae. The plant grows abundantly in the nelgnh ous of 
Lahore as well as in other similarly dry districts in India. 
An active principle has been extracted from this plant, called ‘‘ harmalin,” which 
is supposed to be a specific against malaria. This substance permeates the whole 
plant and imparts to it a peculiarly offensive odour, which has earned for it the name 
of “devil’s bush.” Itis probably this property which insures, in a great measure, an 
immunity to the plant from the attacks of animals. It is believed that even a camel 
would not eat it (Lahore Gazetteer, 1894). 
The only serious pest that the plant has to contend against in nature, excepting 
one or two occasional visitors, is its own peculiar Aphid, which often completely 
smothers the growing shoots. 
Systematic.—Among the Aphididae, up to very zecent times, there were only two 
genera, Hyalopterus (Koch) with H. pruni as the type and Brachycolus (Buckton) the 
type of which is B. stellariae, distinguished by the cauda being longer than the cornicles. 
A number of other Aphids, with similar characters, have now been sorted by van der 
