INSECTS 35 



is a good scavenger, and should be useful in a badly-managed 

 aquarium. 



Unfortunately both Gammarus pulex and Asellus aquaticus 

 find a stagnant-water aquarium unpleasant, and soon die. It 

 is difficult to understand the cause of death, for the writer kept 

 a large number of freshwater shrimps in a jam jar with few 

 casualties, whilst those in the aquarium have died in a very 

 short time. The depth of water cannot be the cause. Asellus 

 aquaticus was found to inhabit the abysmal regions of Lake 

 Geneva at a depth of 130 feet. 



CHAPTER III 



INSECTS 



ALL insects have what is termed a " life cycle," that is, they 

 usually undergo various transformations ere they become like 

 their parents. Everyone is familiar with the caterpillar, the 

 queer and sometimes beautiful creature found enjoying life in 

 the vegetable kingdom, and most people have seen a chrysalis at 

 some time or other. Well ! These are two stages in the life 

 cycle of the butterfly or moth, which consists of : 



The egg, 



The caterpillar or larva, 



The chrysalis or pupa, 



And the adult butterfly or moth as the case may be. 



These transformations are what all self-respecting insects 

 ought to go through, but some do not. We find that several 

 kinds hatch into larva (caterpillar) and subsequently change 

 into the adults without becoming a pupa (chrysalis); whilst 

 again the young springtail is similar on hatching to the parent 

 practically in all respects, except size, thus missing the larva 

 and pupa stages. The above points are of importance, or else 

 the reader will be less able to understand what follows. In 

 short, if the life history is " complete," an insect egg hatches 

 into a larva. The larva feeds and eventually changes into a 

 pupa ; in the meanwhile it eats and sleeps, but gradually altera- 

 tions are taking place in its form and structure, and eventually 

 the pupa case is torn open and the perfectly-formed insect 

 makes its debut. 



Some species of the following families spend their entire lives 



