IJOOK VII. 



INSECTS. 



1113 



7G49. The duration qf insects Is extremely variable: the greatest proportion appear to be annuab 

 emerging from the egg and passing through tne three stages ortheir existence within the space of a year- 

 JBut there are a great number of species, particularly among the beetles, which pass three, and even four, 

 years in the caterpillar state ; and instances are on record of beetles remaining in timber from ten to 

 fifteen years. The greatest proportion of moths are biennial, passing the winter in the chrysalis state 

 and closing their existence in the succeeding summer. The transitory life of the .Ephemera is proverbial; 

 the perfect insect indeed exists but for a day, and seems born only to continue its species j yet in the larva 

 state it enjoys a life of one, two, or even three years. 



SuBSECT, 2. Arrangement or Classification of Insects* 



7650. All insects, as Macleay observes, may be divided into two groups ; 1. Apterous insects, having either 

 no metamorphosis, or only that kind of it the tendency of which is confined to the increase of the number 

 of feet : these, as their name implies, are destitute of wings. 2. True insects, or those whose metamorphosis 

 has a tendency to give wings to the perfect or image state, but never more than six feet. 



7651. True insects are again divisible into two primary groups ; the first of these are organised for mas- 

 tication in their jx^rfect state, and the second are organised for suction alone. Each of these divisions, 

 according to the system of Macleay, contains five separate orders, the principal characters of which we shall 

 endeavour to make intelligible in common language. 



7652. The Mandibvlata, or masticating insects, are furnished with jaws of a horny or membranaceous 

 substance, infinitely diversified in their form and structure. They are divided into the following orders : 



tiy !. 

 country, well known, in their perfect state, to all loTers of ang- 

 ling. Phryganea rhdmbica {Jig. 967. c) may serve si an 2i- 



1. Trichdptera. The wings are four, soft, and 



generally 



., w . ttie lower 



folded when at rest. The insects of this order are compar- 



a tube of its own construction. There are many species in this 

 known, in their pi " ' ' ' ' 



atively few. The caddy, or cadis worm, is the larva of the ample of this order. 



spring fly ( Pbrvginea), and lives in the water, concealed within 



2. Hymeruipiera. 1 he wings are four, clear and transparent. 

 The tai8us (or outer division of the foot) is composed of five 

 joints, and the body is armed with a sting. The bee, the ant, 

 and the wasp, are familiar examples. 



3. ColciSptera. This well defined and most extensive order 

 comprehends all insects known by the name of beetles. 1 hey 

 have two wings, concealed beneath a pair of hard wing-cases, 

 wliich meet close together in a straight line down the back. 

 There are many tribes of these insects, wliich, both in their 

 larva and perfect state, are extensively injurious to man. 



4. Orihiiptera. The true wings are but two, \er\ large when 



expanded, and folded lengthways when at rest. Thev are co- 

 vered, either partially or wholly, by two wing-cases o"f a thin, 

 tough, and rather opaque substance, somewhat resembling 

 parchment, and reticulated with small neives. The leading 

 Characters of this order are exemplified in the Cldtta, or cock- 



roach ; the pest of tropical countries, and frequently trouble- 

 some in our kitchens and larders. 



5. Neurdptera. The wings, with Tery few exceptions, are four 

 in number, clear, transparent, and reticulated with numerous 

 areolets, or irregularly square divisions ; the tail of the female 

 is not armed with a sting. Few, if any, of these insects maybe 

 considered as injurious: some are, indeed, beneficial ; as, from 

 their predatory habits, they attack and devour a vast number 

 of smaller insects. This is more particularly the habit of the 

 green dragon-fly (A'grion vfrgo, ^^y. 967. a\ which every one 

 s, dui 



may see, during summer, hovering over ponds, and flying about 

 like a hawk in search of its prey. The JSph^mera, or day-fly 

 \B. vulgkta, Ji^. 967. 6), likewise belongs to this order; and, 

 although not very numerous in this country, is so abundant on 

 the Continent, that they are collected annually in barrows, and 

 afford to the agriculturist a rich and valuable manure. 



7653. The Haustellata, or suctorial insects, likewise contain five orders. Although apparently destitute 

 of jaws, there is every reason to believe, from the observations of the celebrated Savigny, that the rudi- 

 ments of the masticating organs exist in these insects, but that they are so slightly developed as to be totally 

 useless, and only discoverable under a very strong magnifier. The suctorial insects in their larva state 

 are mostly furnished with strong and well defined jaws, and feed voraciously upon animal and vegetable 

 bodies ; yet, from the perfect insect being supported by suction alone, it is obvious that in this state they 

 can do no injury to the agriculturist. The orders into which they have been divided are these : 



1. Lemtliipiera. Thewingsarefoiir,thin, membranaceous, and 

 covered with a fine powdery substance, which, by the magnify- 

 ing glass, is shown to consist of minute scales, lying one upon 

 another, like those on fishes. The butterfly and moth tribes 

 are familiar to every one, as well known examples of these in- 

 sects, the larva of which are called caterpillars. The Papflio 

 urticiE.or small tortoise-shell butterfly ( fig. 968.), will strve as 

 & good example of the egg (a a), larva (b), and pupa state (c) of 

 most day-flying lepidopterous insects. 



2. Diplera. The wings are two, clear and transparent, 

 like those of the common house-fly. This order is very nu- 

 merous, and contains many insects which are injurious to vege- 

 tables as larvfc, and troublesome to man in a winged state ; as 

 the gnat (Cfilex), whane-fly (Tabanus), crane-fly (Tlpula), &c. ' 



3. A'ptera. Entomologists of the last century arranged all 

 insects without wings under this order; but it is now restricted, 

 by Latreille and Macleay, to such only as have a bivalve articu- 

 lated sheath to their mouth or rostrum, and no wings, as in the 

 case of the common flea. 



4. He7n(ptera. Insects of this order are furnished with two 

 folded wings, covered by wing-case;, also crossing over each 

 other, of a semi-corneous substance, and which are likewise 

 useful as organs of flight. The tarsi are composed of three, 

 two, or sometimes only of one joint, and the body is much flat- 

 tened. The various insects cornmonly called field-bugs, which 

 emit a strong and disagreeable smell when handled, are all ar- 

 ranged under Uiis order. 



."J. Hotndptera. Tliese insects have a great resemblance to 

 the last ; but the body, instead of being depressed and flat, is 



