SIALIBiE. 
143 
lives if food is plentiful but long ones if it is not, and some species normal¬ 
ly have long lives (special parasites, such as Bombyliids , Conopids). 
Few Hemiptera have been reared, and we must fall back on what is 
known of the periods at which the imagines appear. A few Pentatomi- 
dce appear to breed often in a year, whilst some are probably two-brood¬ 
ed, a rains and a dry weather brood ; some are probably only one- 
brooded. The same is.probably true of Coreidce. Lygceidw and Pyr- 
hocoridce appear to include more species which breed several times, as do 
the Tingidw . Reduviidae are probably few brooded, as well as Capsi- 
dce, but the latter in some known cases breed quickly. 
Cicadidce possibly all require at least one year, while some are very 
long-lived, and it is quite possible that our Indian species follow the 
examples of the known long-lived ones. The smaller Homoptera (Fulgori- 
dce , Membracidw , Cercopidce ) are probably two or more brooded, but 
it is doubtful if any have more than four broods yearly owing to the lack 
of food. Aphides are comparatively short lived with plenty of food, but 
as they are viviparous, an aphis may often live to be surrounded by sever¬ 
al generations of children, grandchildren, and so on. Given good cir¬ 
cumstances the number of broods in a year may be very large, without 
the life of the insect itself being naturally very short. Aleurodidce and 
Coccidce are, for so small insects, apparently long-lived, but they appear on 
the whole to have several broods a year, while some are only one-brooded. 
The student will recognise that so brief a summary is of little value 
save as a suggestion and as an indication of the scope of the relative life. 
Further details are given under each family. 
There are two methods of finding the length of life of insects, one 
the actual rearing or observation of the living insect in all stages, the 
other the knowledge of the seasons at which the imago appears and the 
length of its life ; an insect that appears but once yearly may have a 
yearly period or one in multiples of years, but cannot have a less period 
than a year. The duration of life in the long-lived American Cicadas 
was deduced from the years in which the imagines appeared abundantly, 
a matter of such importance that records extending back many, years 
gave the necessary information. 
SlALIBiE. 
Wings of nearly equal size, hind icings not folded ( cf. Perlidce ), at an 
angle over the abdomen when in repose. Antennce long. The wings 
are not closely reticulate (cf. Hemerobiidw). Tarsi five-jointed . 
Larva aquatic , with a quiescent pupa . 
A small group of moderate-sized insects, distinguished by the wings 
and five-jointed tarsi from the Perlidce which most resemble them, 
