LN/UUlUUtt TO TUK tVHNlt CUUP. 31 f 



I, or neglecttfil roots lefi in the soil, and growing up with the corn cro]> 

 still furtlior prolong their existence, until tho seedlings of chu next orofiy 

 shewing themselves in a state to which they have a still greater prudileetion,) 

 invito them forth firom their hiding places, to the great chagrin of the cul- 

 tivator, who, for tho tirst time, becomes aware of the presence of thousands 

 of his tiny foes, ready to lay waste the produce of his fields. As a pupa, 

 or chrysalis, a state in which tho embryo of most insects resists the severest 

 winters, numbers probably remain in the soil, and are hatched into wing- 

 ed insects in spring. Ono of the boneflts derivable from the practice of 

 «ftting off turnips by sheep folded oit the ground, is certainly the destruction 

 of many insects m this condition. 



Whilst feeding on tho turnip crop in an advanced state of ^owth, the 

 presence of the beetles is scarcely perceptible ; it is owing to their attacking 

 tho tender gorm, just as it emorffes from the soil, and eating off the seed- 

 leaves which supply the plant^ earliest nutriment, as likewise tb« true 

 leaves, as soon as tiiey appear, that they become a plague. The evil is 

 greatly aggravated in a dry season, with a parching wind, and much sun- 

 shine ; as the edges of the wound are shrivelled up as soon as it is inflicted; 

 whereas, in a moist atmosphere, with a plentiful supply of sap from be- 

 neath, the hurtful effects of evaporation are, in some respects, neutralized. 

 In some insects, th^ grub subsists ou a different kind of food from that pre- 

 ferred by the insect evolved from it ; but, in the present case, the plant has 

 to sustain the attacks of the larva, in which stage the voracity of an insect 

 is at the extreme, as well as to support the parent insects and all their 

 progeny when they have become beetles. The beetle lays its eggs on the 

 underside of the turnip leaf, and they are hatched in ten days. The worm 



firoducod betakes itself to mining between the upper and under skins of the 

 eaf ; durin»' which process, it devours only the .soft, pulpy, internal parts. 

 It feeds witliin its burrow for sixteen days. Its change into tho pupa state, 

 during which it lies quiescent, without sustenance, and incapable of receiving 

 any, takes place in the ground, under tho shelter of the turnip leaves. 

 Making its w^ay through the cuticle, it enters into the soil about an inch and 

 a-half, where it remains for about a fortnight, when it re-appears as a winged 

 beetle.* There are four or five broods in a season. f 



From this detail the following results are deducible :— 1. As it requires 

 forty davs, although in certain junctures the inactive stages may bo ab- 

 ridged, before the insect arrives at its final condition, and ten days ere 

 its grub commences operations, it would appear that the greatest injury to 

 the earliest sown crops is occasioned by the full grown insects that first ar- 

 rive upon the ground ; whether they are the remains of tho preceding year's 

 broods ; their descendants, hatched in the early months, on native plants; 

 or, the production of pupae, that have lain in the soil of adjacent fields till 

 a milder temperature has enabled them to complete their transformations. 

 2. The eggs of the insect are not affixed to the seed, nor committed to the 

 earth with it, as some crude observers have confidently affirmed. 3. The 

 insect does not originate from the manure, an opinion that has likewise 

 l)eeu Uroached. The insects found there are adapted to live upon pu- 

 trescent eubstarvces alone; the beetle, in its different stages, lives exclus- 

 ively on livint^ herbage. Equally ridiculous is the idea, that it is tho pro- 

 duct of putrefaction ; a doctrine that might well be consigned to tho cata- 

 eombs with its originators.} 4. Neither does the insect exist in the soil ; 



* Transactions of the Entomolofrical Society of London, ii., part L, 1837. Entomologi- 



cal Magazine, v., 342. 



♦ Curtis in English Ajrvic. Soc. Joui.,li.,(«/ «t^ Gaideners'iJhroniclo, June22, 1844,p.41S. 



I The EKyptians bad recourse to tho doctrino of equivocal generation to explain the 

 origin of the iinmense awarinn of insects and textiles tiiat appeared simultaneous with 

 the subsidence of the Nile. As regards the production of insects and the lower olaasfs 

 of animals, it id still a favourite popular tenet. Some of tho!ie philosophers who main- 

 tain it, perhaps do to, not so much as the rcHult of opinion* as of »truug traditional 

 pr»'judicc. 



