140 
NEUROPTERA. 
Indian species, and these insects appear during long periods in the hot 
weather and rains, but not in large numbersat any one time. As these 
insects in their feeding life live a purely aquatic life, there are none of 
economic importance and the group, as a whole, has attracted little atten¬ 
tion in this country. The number of species known is small, as they are 
not attractive to collectors. 
In his monograph, Eaton describes the known Indian and Ceylon¬ 
ese species (Trans. Linn. Soc., Zool. III). Eaton also mentions ten spe¬ 
cies from India (J. A. S. B., LX, p. 106) and discusses them, mentioning 
also that McLachlan possessed nine species from Tenasserim. The total 
recorded by him is twenty-two species, but our common plains species 
are apparently undescribed, the recorded species being from eleva¬ 
tions above 4,000 feet in Ceylon or the Himalayas in most cases. 
Collecting .—Imagines and sub-imagines are best preserved in spirit 
as their integuments are weak, but when plentiful, a series may also be 
pinned. 
THE RELATIVE DURATION OF LIFE. 
The actual duration of life measured in human units, is a matter 
of very considerable variation among the diverse forms of insect-life. 
From the extremely short-lived Drosophilid fly to the long-lived Cicada, 
there is an infinite variety ; this is a matter of small importance since the 
passage of time has a relative value and the insect which lives for but a 
few days may pass through as many experiences as a human being in as 
many years. The point is, perhaps, interesting as popular ideas are often 
extremely erroneous and forget to take into account the fact that a 
winged insect whose life is but a day may have passed weeks or months 
in an immature form. 
Factors which govern the duration of life are many and varied ; 
fall of temperature suspends activity to a greater or lesser extent, and, 
while prolonging the actual length of life, does not add to the active 
living period. Abundant food by hastening maturity and the develop¬ 
ment of the reproductive system may materially shorten the life of an 
insect; unnutritious food or the lack of food may immensely prolong 
life either by preventing the immature insect from deriving sufficient 
nutriment from its food or by checking the development of the repro¬ 
ductive organs, so that life is maintained for long periods until the eggs 
are formed and egg-laying becomes possible. The absence of the larval 
