26 METAMORPHOSES OF INSECTS. 



oxygen ; but when they are seemingly dead from this cause, they 

 for a long time retain the power o;' being restored to life. 



52. The sexes are distinct in these animals, and frequently the 

 males and females differ widely from each other. There fre- 

 quently exists at the extremity of the abdomen of the female an 

 ovipositor or borer or some other organ by means of which she 

 prepares a hole for the reception of her eggs. Some are vivi'- 

 parous, but almost all insects lay eggs, but they do not deposit 

 them wherever they may happen to be ; they require them to be 

 carefully lodged in some place where the young animals on 

 escaping can readily obtain the kind of food proper for them. In 

 this respect the instinct of insects is most surprisingly developed, 

 and it would be interesting to study the various plans they adopt 

 to secure this object, but our present limits will not permit. 



53. When an insect escapes from its egg, it sometimes 

 possesses the same form which it is to preserve through life; 

 but in the ^'reat majority of instances, it differs more or less 

 from its mother, as well as from the form it itself is destined to 

 assume. Before attaining its perfect state, it undergoes con- 

 siderable changes, which are designated under the name of meta- 

 morphoses ; it passes through two successive conditions, termed 

 the larva (Latin, a mask, because the perfect form of the insect 

 is concealed as it were under a mask), and nympha, pupa, or 

 chrysalis (from the Greek, chrusos, gold, because the transparent 

 covering in which the animal is enclosed while in this state, in 

 many instances reflects a metallic lustre). When it has passed 

 through these two stages of its metamorphosis, it becomes a 

 perfect insect, "and is then called imago. But these changes are 

 not always of the same nature; some insects experience only a 

 partial metamorphosis, some a demi-metamorphosis, and others, 

 a complete metamorphosis (from the Greek, meta, indicating 

 change, and morphe, form 1 ).' 



54. Those insects which undergo partial metamorphosis ac- 

 quire after birth a number of legs, more or less, but always 

 remain without wings. The Parasi'ta and Thysanou'ra experience 

 this description of metamorphosis. 



55. Those insects which undergo demi-metamorphosis differ 

 very little from what they are to become ; their larva resembles 



52. How are the young of insects produced ? 



53. What is meant by the metamorphosis of an insect ? What is a larva ? 

 What is a nympha ? To what condition of insects are the terms pupa and 

 chrysalis applied ? What is an imago 1 Is the metamorphosis the same in 

 extent in all insects ? 



54. What is meant by partial metamorphosis? 



55. What is meant by demi-metamorphosis ? 



