232 



THE AMERICAN 



IfOXIOUS LABV^. 



liV Dll. WM. LE BARON, GENEVA, ILLS 



Wliilst insects are much more beautiful and 

 perfect, aud consequently more attractive and 

 interesting, both to the entomologist and the 

 amateur, in the imago or winged state, than in 

 the lai-va or grub state, yet it is in this last con- 

 dition that they are of cliief importance to the 

 farmer and horticulturist. This we shall easily 

 understand from the following considerations. 

 In tlie first place, it is in the larva state that the 

 insects accomplish the whole of their growth; 

 no insect increasing in size after it has attained 

 tlie winged form. It is therefore in the larva 

 state th:it tlic nii'ati'st aniount of food is required, 

 aii<l :irc(ir(liiii;|y il i- in this state only, with a 

 few exceptidiis. llial insects commit those exten- 

 sive ravages which often render them the scourge 

 of the husbandman. 



Secondly, many insects which in the lai-va state 

 are furnished with mandibles or teeth fitted for 

 gnawing herbage, are so completely changed, 

 that in the perfect state, the mouth consists of a 

 long flexible tube or sucker, incapable of injur- 

 ing vegetation. Such are the extensive tribe of 

 caterpillars, which, in their perfect state, become 

 converted into moths or butterflies. 



Thirdly, as a general rule, insects live much 

 longer in the larva than in the perfect state, and 

 therefore have more time for mischief. Many of 

 the Lepidoptera live several months as larvae, 

 but only a few days as imagines or perfect in- 

 sects. Some of the most pernicious Beetles, 

 namely, the May-beetle, which comes from the 

 Wliite grub, and the Two-striped Saperda, wliich 

 is the parent of the Round-headed Apple-tree 

 Borer, exist three years in the larva state, and 

 not often more than as many weeks in that of 

 the perfect insect. 



It is in the lai-va state, therefore, we repeat, 

 that insects are of the most importance to the 

 agiicultuiist, and it is natural, when he meets 

 with these mischievous creatures, that he should 

 feel interested to know what is their name aud 

 nature, and into wliat kind of winged insects 

 they will ultimately be changed. It is in order 

 to aflTord some assistance in gratifying this laud- 

 able curiosity that we have drawn up a few 

 practical generalizations, which are recorded in 

 the sequel. 



Insects, with respect to their transformations, 

 are divisible into two widely different sections. 

 In one the metamorphosis is said to be incom- 

 plete ; that is, the insect retains the same form, 

 or nearly the same, in all its stages of lai-va, 

 pupa, aud imago, and is active in the pupa, as 



well as in the other states. The pupa is distin- 

 guished by having ruclimental wings, and the 

 imago by having wings fully developed. The 

 grasshopper furnishes a familiar example of tliis 

 kind of metamorphosis. 



In the other section, the metamorphosis is 

 complete; that is, the insect undergoes such a 

 total change that its several states bear no re- 

 semblance to each other, and the insect is inac- 

 tive in the pupa state. The caterpillar changing 

 to a chrysalis, and then to a moth or butterfly, 

 furnishes a well known instance of complete 

 metamorphosis. To the former division belong 

 the orders Orthoptera (Grasshoppers, &c.) and 

 Ilemiptera (Bugs, Leafhoppers, &c.) ; wliilst 

 the latter inelndes tlie vast majority of insects, 

 constituting I lie rcinijinhensive orders of Coleop- 

 tera or Beelhs. Leiii(lni)iera or Scaly-winged 

 Flies, Hymenoptera or Clear-winged Flies, and 

 Diptera or Two-winged Flies. The order Neu- 

 roptera, which is in a gi-eat measure aquatic, 

 forms a connecting linlc between the two sec- 

 tions, the greater number being active in all 

 their states, whilst in a few families, such as the 

 MyRMELEONiDvK (Aut-lious), and the Hemebo- 

 BiiD^ (Lace-wings) , the species undergo a 

 complete transformation. 



If, in accordance with the views of some re- 

 cent authors, we unite the anomalous group of 

 Strepsiptera to the order Coleoptera, and more- 

 over include the harmless Phryganeid^ in the 

 order Neuroptera, then we can make the broad 

 assertion that every order of insects contains 

 species injurious to mankind. By far the larger 

 proportion of noxious insects belong to the two 

 orders Coleoptera and Lepidoptera, either one 

 of which contains nearly as many injurious spe- 

 cies as all the other orders together. 



Ot the one hundred and seventy-eight families 

 recognized by Mr. "Westwood in his classiflcation 

 of insects, sixty-five, or rather more than one- 

 third, contaui noxious species. Of these sixty-five 

 families, I find but six in which the species are 

 injurious exclusively in tlie imago state, viz., 

 the Cantharides, the Rutelidie and the Cetoniidse 

 amongst the Coleoptera, the Formicidae (Ants) in 

 the order Hymenoptera, and the Culicidse (Mos- ) 

 quitoes), and Tabanidas (Horse-fiies) in the order 

 Diptera. And of these six, none except the Can- 

 tharides can be classed with the more seriously i 

 injurious insects. The species of all the other ) 

 fifty-nine families are injurious exclusively or ) 

 chiefly in the lai-va state. In some instances, 

 indeed, and especially amongst the phytophagous ) 

 Coleoptera, namely, the Chrysomelidie and their ' 

 allied famihes, and also in those orders wherein ' 

 the species undergo an incomplete metamor- 



