LIFE HISTORY AND HABITS; 



are alike in form or habits, so that we must have a clear conception that 

 we are not in a world of clear-cut definitions and distinctions but in one 

 whose first charm lies in its infinite variety. 



Eggs. 



Insects are not produced spontaneously from plants or from dirt, but 

 arise from eggs laid by the parent insect, or, in rare cases, are born alive. 

 No case is known of insects having been produced in any other way, and 

 in tracing the life of an insect we may commence from the time the parent 

 lays the egg. Insects often appear suddenly in great numbers, and ignor- 

 ant cultivators believe that they have fallen from the sky or are due to 

 a change of weather or some similar cause. The appearance of an insect 

 in small or large numbers is not a supernatural phenomenon and can only 

 be caused by the parent insect having laid eggs or produced living young 

 in or near that spot at some earlier time ; the eggs may not have been 

 seen and may have been there for several months, but in every case if we 

 could go back far enough we could trace them to the parent insects. 

 Reproduction in the insect world is a process similar to that of the higher 

 animals and no more mysterious ; it depends upon simple causes which 

 are fully capable of investigation and differs but little from those which 

 bring about reproduction and multiplication in other living creatures. 



In almost all cases, the eggs are produced after the mating of the 

 male and female insects ; there are a few groups of insects in which 

 males occur rarely or not at all ; the females then produce eggs or living 

 young without the co-operation of the males, but this is confined to a 

 small number of insects and in them occurs regularly. If a^bred female 



moth is kept alone in a cage, she 

 may lay eggs, but they are imperfect 

 and do not hatch ; an aphis, on the 

 other hand, may produce eggs or 

 living young without any male being 

 present, many successive genera- 

 tions being thus produced without 

 the intervention of any male. In 

 some groups, insects are born alive. 

 p, T _ Q , In the aphides this is the normal 



xIG. ol. 



Cockroach Egg case. (Magnified.} process during part of the year, no 

 eggs being formed, but the virgin female producing living young, 



In some flies, the female carries the fertilised eggs within her body 

 awaiting a suitable opportunity to lay them on sufficiently decayed matter. 



