CONSIDERATIONS. • 



iMonfl. u deflned iu the foregoing iwragraph, are still very closely related to other 

 daMM of aninuls : thus they resemble the Myriapodes in the annular or jointed structure, 

 •nd In th«? iinoormnlnn of two antennae, but differ from them by the division of their bodies 

 iBto thice segments, while the Myriapodes are composed of many rings, to each of which 

 then b provided • pair of legs, as in the family of animals called Centipedes. They re- 

 semble the spiders, or Arachnida', somewhat in the division of the body, but the head in 

 spiders is soldereil to the thorax : they are also destitute of antennse ; the nervous system 

 la condensed into fewer central ganglia, and sometimes their respiration is analogous to 

 the pulmonary, the air being received into sacs or bags. They resemble the Crustacea in a 

 few points, but differ essentially from them in the character of the respiratory apparatus, 

 Inasmuch as the Crustacea are provided with organs analogous to the gills of fishes. The 

 reaemblance which insects bear to the worms, Annelides, is' the annulated structure : those 

 worms have neither antennse nor feet, and, as to sex, they are mostly hermaphiodites. In 

 addition to the foregoing, I may add, none of the classes have wings but insects, and their 

 metamorphoses are of a different character, consisting mainly of a casting of the integu- 

 ments as iu the crab and lobster. 



All Insects are oviparous, or spring from an egg laid bef(a*e the birth of the individual. 

 A few examples are known where the egg is retained in the body, and there hatched. 

 These eggs are often carefully concealed, and hence are discovered with difficulty : it is 

 owing to this circumstance that they multiply to an injurious extent, and are often capable 

 of devastating extensive territories. They are, however, generally laid upon the bodies 

 which are to provide the food for the young : those which subsist upon herbaceous plants, 

 are found ujwn or near the foliage ; those which feed upon wood are deposited in holes, 

 or in cracks and crevices of trees, into which the young animal immediately begins to 

 penetrate ; or, which is -equally bad, the egg is deposited in the rudiments of the fruit, and 

 will be ready to devour it when it is mature. 



Insects are extremely jh-oMc, but the different species vary exceedingly. According to 

 a statement in the Naturalist's Library, a certain large fly {Mesemhrina meridmna) lays only 

 two eggs ; while the female white ant lays probably not fewer than forty or fifty millions 

 in a year, which are extruded at the rate of sixty in a minute when engaged in the act*. 

 This statement embraces the extremes. Others are known to lay, as the queen bee for 

 example, fifty thousand ; female wasp, thirty thousand, though generally only from two to 

 three th<)usand. The eggs of the whe^t fly are not very numerous, and probably less than 

 one hun<lred ; yet even in that small number the increase will be sufficient to secure the 

 destruction of the wheatfields in a large district. But many insects produce several broods 

 in a season, and some of the most prolific produce several generations of young, consisting 

 mainly of females, which are capable of laying eggs as soon as they have reached a stage 



• NaturalW* Library, Introduclion, pp. 72, 78. 



