J i.lMIUl. CONSIDERATIONS. 



Insects, as defined in the foregoing paragraph, are still very closely related to other 

 ises of animals : thus thej resemble the Myriapodes in the annular or joint* «1 structure, 

 and in the possession of two antenna-, but differ from them by the <li\ ision of their bodies 

 int>> three segments, w hi !<■ the Myriapodes are composed of many rings, to each of which 

 there is provided a pair of legs, as in the family of animals called Centipedes. They re- 

 semble the spiders; or Arachnids, somewhat in the division of the body, hut the head in 

 spiders is - 'Mend to the thorax : thej are also destitute of antenna ; the nervous system 

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

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

 points, but di B c • - atiallj from them in the character <>!' the respirator] apparatus, 

 Inasmuch a> the Crustacea are provided with organs analogous to the gills of fishes. Tlie 

 mblance which insects bear t" the worms, Annelides, is the annulated structure : those 

 worm- have neither antenna- nor feet, and, as to sex, they are mostly hermaphrodites. In 

 addition to the foregoing, I maj add, none of the classes have winus but insects, and their 

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

 ments as in the crab and lobster. 



All insects are oviparous, or spring from an egg laid before the birth of the individual. 

 A tew 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 

 owin:* 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 tin- young : those which subsist upon herbaceous plants, 

 are found upon 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. 



bisects are extremely prolific, but the different species vary exceedingly. According to 

 a statement in the Naturalist's Library, a certain large fly {Mesembrina meridiana) 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 ol sixiy 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 thousand. The e<. r ns of the wheat fly are not very numerous, and probably less than 

 one hundred ; 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 



• Naturalist's Library, Introduction, pp. 72, 73. 



