XX. H$’ory of %pula Tritici, and Ichneumon %pub, with j m e Ob/cr- vations upon other Ih@’s that attendthe Wbeat, in a Lelter t o Thmas MarJarn, Ef& Sec, L, S. By the Rev. Wilham &-by, F. La S.

MY DEAX FRI&D. Blir~attt, Sept. eg, 1797.

W H E N you left me in July lafi, you defired me to continue my obfervatioiis upon thofe infeCts that iiifefi the wheat;

and particularly to endeavour to complete the hitlory of the larva, of which you have given an account in the 3d vol. of the TranJ atjions of the Linnwan Society *, and which, with great jufiice, you’ 1

fuppofe to be the principal enemy of the grain. In compliance with this reclueit, I have endeavoured to trace it through all its metamor= phofes, and to afcertain, in fome meafure, the quantity of mikhief which i t is capable of doing-with what fuccefs you ihall now hear; and 1 ihall add fuch othcr circumfianccs relative to this and other infe&s which attend the wheat, as have occurred to my obfervation. What I have collefied, although far from being a complete hitlory of all the inf& infeiters of that grain, may afford fome few hints which may pofibly be of ufe to afifi the inveftigations of abler

* rran/; Lhu. Sor. vol. iii. p. 242. Tab. xxii. fig. 9. 10. XI. 12.

Nat uralilts,

Naturalifis, and, in conjunaion with your own obfewations, and the . . information you will procure from the ingenious and accurate Mr. Markwick aiid other friends, be not unworthy of the notice of the public.

In the year 1795, when you firfi began to invetligate this CubjeO, I obferved very few of the larva in queition; and confidering the Thrips plyfoppus as occafioning the greatelt quantity of injury, my chief attention was direAed to that infe& ; but in the prefent leafoil I have more particularly attended to the former. Wherever I have taken my walks, I have made it my bufinefs to examine thoCe fields of wheat through which I have pared, and I have fcarcely paffed through any in which fome florets, of every car that I examined, were not inhabited by there ~ N V X ; and this has often been at fome Sifiance from hence. But although I have found the larva: To abundant, the pupa has very ikldom occurred to me; fo that for fifty of the former, I think I may fay without exaggeration 1 have fcarcely found one of the latter. As many as I collelked, I put into a tumbler covered with gauze, in which they remained fome time without any imago making its appearance. At length I obferved the exuvia of one lie at the bottom of the glafs; but the imago, I fuppofe, had made its efcape through the gauze, as I could not find it. Upon this 1 put the remaining ones into a fmall phial, the mouth of which I fecured with gauze four tinics doubled, and tied clofe. About three weeks fince, examining this one day, I obferved a fmall fly walking up its fides : L opened it carefulIy, and Cecured my little animal, which upon examimtion nppenrcd to be a very minute %pula, nearly of the colour of the p u p . I t is not delcribed in Gmelin's edition of the .!$j?ernu NofurM, nor by any author that I have accefs to; therefore I ihall dei'cribe it, arid the little J C ~ I I P I ~ / U which dcpoGts its egg in its 1zri.a.

'T 1 F c' L A,

232 Rev. Mr. KIRBY'S l?$ory of

TIPUL ,4. AliJ incumbentihs. Cuhcformcs.

Tri/ki. T. ferrugineo-rufa, a h hyalinis margine pilotis, oculis nigh. Minima auran tiaca. Antenna moniliformes thorace lon- giores. Akc pilis ciliata. Peder longiufculi.

Longitudo ferh linearis. Larva faltatrix, apoda, citrea, marginata rnargine plkato-papila

lofo, capite acuto, caudi truncati.

Habitat in Tritici fpicis. Pupa anguita, utrinque acuta, rufefcens.

ICHNEUMON. Minut< ah&& mabJ$%.

I. niger, antennis baG pedibufque rufis; tibiis poiticis clavatis apice nigris.

Minutifimus, iiiger, nitidus. Anterzne fiaat;e, vibratoriae, arti- culo primo longo rufefcenti. Ah aveniz immaculatz corpore longiores. Ah&men obovatnm, deprefium, i'ubfeefiile. Tdk clavatae, pmfertim poftica.

S@h.

Longitudo infra linearis. Habitat in larvis Tipuh Irriici, ovum unicum deponens in

iingulis.

After I had taken my little'Z'z)ula, I unfortunately loft it. I had faitcned it upon a piece of paper with gum water, and left i t for a time in an open box, that the gum might dry. I fuppofe iome .other i d e a took tha t opportunity to devour i t ; for when I returned t o put it to a place of greater fecurity, it was gone, and ever Gnce I have watched in vain for the difclofure of another.

It

7iPula Tritici, arid Ichneumon T+uLx. 233

It is fingular that this fpecies of T;puZa, which muit neceffarily be very common, ihould never have been noticed. So often as I have been, and a t all times, in the corn-fields, with my attention always awake to entomological fubjeas, 1 do not recolleA ever fee- ing it before. Since I lofi it, I have fearched for it in a field where I found the larvse in the greateit plenty ; I have examined the barn where the corn from that field was laid up ; and in both in- fiances was equally unfuccefsful. From thei'e circumitances it ieems probable, that althouqh one or two mizht be difclofed with me, by being placed in a fituation where the fun h o n e upon them, fooner than their natural feafon, yet t h a t in general the fly does not make its appearance until the Spring, fo as to be in reacli- nei's to depofit its egqs in the wheat, when it has matfc fo miicli progreCs in gronith, that the larva may be hatched about the tiinc of its going into bloffom. And I am confirmed in this opinion by another circumftmce : A few days fince, with a fine needle, I care- fully took off the thin membrane from two of the p u p which I had referved, that I might fee how near they were to a change of itate ; but infiead of dii'covering the lineaments of the future fly, the infeeEt was flill in the form of the larva*: fo that probably the pupa is not ufually complete until the Spring, and the iiifeA inclofcs itfelf iii a thin nieiiibrane to proteki itfelf from the cold of the Winter.

I obferved above, that the pup^^ which I met with bore no pro- portion in number to the /ifrz~'cz. I have k e n more than once ieven or eight florets in an ear inhabited by the latter, and fometimes fo m a n y as thirty i n a fingle floret, i l d o m I d s than e i g h t or nine, a n d

* It mny be oliji.c'tci1 that tlli , v . is probnbly the larva of the L h r e u m n , which 11 Id To tllis I reply, that it W A S in colour, form, and i n C T C Y ~ ~ detoured that of the TI)I//~.

refpetl for-~attly lirnilnr to the latter that i t coiild be noother. Vor,. IT'. I 1 11 y e t

234 Rev. Mr. KIRBY’S H$?wy of

ye t I have fcarcely ever found inore than one pupa in an ear, and had to examine feveral t o meet with that. W h a t then becomes of the remainder of the lame .? Are they deflroyed by that of the Ich- lieurnon? or do thcy become the prey of foine other infe& ? or do they fall to the groiind Xvlien they affume t,he pupa, and remain there until the following Spring ? To give a pofitive anfwcr to any one of thei‘e queries I ilia11 not pretend ; 1 will only relate circumitances, a i l d point out what from them appears to me to be mofi probable. ?‘he p u p that I have obierved have genci-ally been fomcwhat at- tCicheci to t l ie grain, and, what is worthy of notice, I never found then1 within thotc Aorcts wheic the lari-z had taken up their refi- dence ; they ken1 in \ ariably to choofe for their habitation, in their intermediate fiate, one where the grain is uninjured, to which they niay attach themfelves. A queftion here arifes, how they contrk-e to get from one floret to another, having no feet? but as I have never k e n them do this, I will not attempt to conjeAure how they do it. In the field above-mentioned, I took u p many roots of flub- ble, with a large lump of earth ro~ind them, to fee if I could dif- cover any of the pupz concealed in it ; but i f they were there, they efcaped myeye, from their minutenefs: yet it feerns not probable, nor analogous to the general proceedings of nature, that it ihould be in- different to themwhether they go under ground,or remainin the ear, when they aKume the pupa. T h a t they are defiroyeli by any other i d e a than the Icbneutmn, I have no rcafon to believe, having never Eeen them attacked by any other; tlicrefore it feems to me moil proba- ble that this little fricud to man is the deltrayer of by far the greatefi part of them. I f this be the cafe, what a benefaAor to the human race is this diminutive animal ! and how ought we to admire and adore the wifdom and goodnefs of Divine Providence, in thus iettiiig bounds to the ravages of an i d e a , which, however infignificant it

may

\

'Tipula % itici, atiJ Ichneumon '?;PuLt. 235

unav kern a t firit fight, mi;;ht, if pcrmitte4 to exceed its due limits, deprive us of the ftaff of bread, and almott occafion the deitruttion of our ipecies ! T h e fuperltition of the Ancients, had they been acquainted with the advantages which appear to I)e dcriirc.i to man through the initrumeiitality of this important though minute link in the chain of creation, would have cre&ed altars to it, as to a beneficent deity : Can we, who enjoy the clear light of revelation, do lefs than adore and extol tha t goodnei's, which thus prei'erves a due balance in his works, and fays to the deltroyer, Thus far ihalt thou come, and no further * ? Indeed the numerous fpecies of the genus li.hncumon ieem to have been created on purpofe to keep within due bounds the other tribes of iiife&s. Any pcrfon who has obferved the depredations committed in our gardens by the caterpillar of the cabbage butterfly, may conjefiure to lvhat extent they would be carried, were it not given in charge to the Ichneumon of that inlet9 to keep them within their afigned limits. 111 a. word, were it not for this philanthropic genus, we lhould not be able to itir, nor even breathe, without being annoyed, nay Cuffocated by myriads and myriads of troubleCome animals, which are now taught to know their proper bounds, and a n h e r the ends for which they were created. But why do I thus moralize to yoii, to lvhom thel'e refleoions are perpetually recurring ? I ihal l therefore returii to my hiltory.

I t is Gngular, but molt people who are acquainted with the larva of the Tipula Trihi miltake this friendly I c h n t ~ x m for its pa- rent, and thus impute all the mif'chief to the very creature which

Finis creationis telluris efi gloria Dei, ex opere naturz per hominem folum. Omnes res creatae funt d i v i n ~ fapienti% et potentia tetles : divitia felicitates humans.

Ex harum ulu bonitas creatoris ; ex pulchrediiie fapientia Domini ; ex ceconomia in ~ 0 1 1 -

Lim.

ferrvatione,prcpcvricnr, renovatione, potentia majefiatis elucet. hi. H h 2 is

236

is appointed to prevent it.. It is Come fatisfa&ion to ine to con- firm your opinion" and do jutlice to our little benefaaor, and to point out where the odiuni ought to fall.

To fee our little Ichneumon depofit its q g in the caterpillar of the wheat fly, is a very entertaining fight. I n order to enjoy this pleafure, 1 placcd a number of the latter upon a iheet of white paper, at no great diltance from each other, and then fet an Icbnetfmwz down in the midit of them. She began immediately to march about, vibrating her an tennz very britk1y:--a larva was foon dif- covered, upon which h e fixed hcrklf, the vibratory motion of her antennae increafing to an intenfe degrec ; then bending her body obliquely under her breafi, Ihe applied her anus to the litrva, and during the infextion of her arnicas, and the depofiting of the cqg, her antennz became perfektly fiill and motiddefsi WbiM t i i s operation was performing, the larva appeared to feel a momentary fenfation of pain, for it gave a violent wriggle. When all was finilhed, the little Ichneutnon marched off to feck for a fecond, which was obliged to undergo the Ciime operation, and To on to as many as it could find in which no egg had been before depofited- for it commits only a Gngle egg to each larva. I have feen it i?.c- que~itly mount one which had been pricked before, but it loon dil- covered its mifiake and left it. T h e t z e of it Ls fo near that of thc ~ i u l a , that I imagine the larva of the latter could not fupport morc than one of the former, and therefore infiinft direas it to depofit only a tingle egg in each ; befides, by this means one Ichngurnen \vitl deftroy a n infinite number of larvz.

T h e 1rrri.a of the %)h 7r-h;ci (as Mr. RInrkwick; in his letter to you, dated July I 7, 1797, has well conjet3urcd) appears to feed upoll

* Iran/ Linn. Sot. vol. iii. p. 243.

the

the pollen or dun of t h e an them, for in thofe florets in which i t refides the germen never fwells, and t h c an the r2 are perfifling; f rom which it feems evident t h a t thc impregnation of t h e germen is prevented, either by t h e infea's ufing fornc means, perhaps a kind of gluten, to prevent t h e pollen from buriting from thc an- t h e m , or, vice ve@, by doing foinething to t h e itigma to prevent t h e fertilization of t h e germen. T h e pollen of three a n t h e m is a itore which will maintain fomctinies thirty of there creatures, from t h e time that t h e wheat is in bloffoin, until it is nearly if not alto- gether ripe. I could never diicovcr that the grain was injured in any other way by this infe&, but it invariably produces the inani- timi of it in t h e floret which it inhabits. I t may always be de- tec'ted by the difcoloured appearance of the bnfc of t h e coroll~, , which is its d u a l itation.

Although Mr. Markwick could not difcovcr any damage done to t h e wheat in t h e year 1795, yet, upon a c lokr examination in t h e prefent year, that gentleman feems convinced t h a t t h e inanition of t h e grain takes place wherever t h e larva makes its attack, as appears by his letter above quoted. My own obfervations fully confirm this opinion ; ar,d thc nifchief occationed by i t will appear to you very confiderable, at leait in this nciShbourliood, when you weigli t h e following rerult of a particular examination of my own, y h i c l i had this circumfiance for its obje&.

T o arccrtain the qilantity of mifchicf p d i i c e d by our ?$zf/d

n.ithin particular limits, I wcnt to a field of fifteen aci'es, w h i c h w a s plantcd partly with nrliite and partly \\.it11 red wheat, I n this ficld I too!; ii\,e itations, one 011 each tide, a n d one i n t h e centre.. I n each itation I ex;imincd a certain number of cars, grain by grain, without icle2lion. T h c reCult was, t ha t in thirty ears of white wheat, feverity-thrce grai:is wcrc dcflroyed by thc larva, which is a t t h e

ratc

rate of not quite two and a half grains to an ear; a i d in twenty ears of red \\heat, twenty-nine grains were deflroyed, which is neatly a t the rate of one and a half grains to an ear. Take the whole to- gcther, and the proportion nil1 be about two g a i n s in an ear, \vhich I fuppok may be about a tnentieth part of the produce, and would make a difltrciice of a t leait five coomb in the crop in this field. T h e white wheat in thisinfiance was moit expofed to the attack of the infel-3 ;-whether this be generally the cafe, mult be determined by future experiments upon a more extenfive kale. LeaR mifchief feemed to be done on the South GJe of the North hedge ; but no pal t ekaped wholly-not an ear' I examined but what had fufiained ibme injury. From the field that I have been fpeakhg of 1 went to another, which was fown later in the Autumn : in this I found fc'carcely any of the larvae; but it was very much infeited by the Aphis, called in Mr. Markwick's letter above-mentioned the Dol- phin*. T h e fainc i'pecies of Aphis is fufficiently common upon barley and oats, as well as wheat : I found very few of there in the firtl f i d . T h e red gum, which is undoubtedly a kind of Fungur, appears to me totally unconne&ed with the infeats that infelt t he wheat: in the field where I found an infinity of the larvz of the S p d a Tritici, and Tbt.$s pbjopris, I fcarcely found any

* Pollibly this may be the Aphis Avrm of Fabricius : but a6 he has given M) defcription

A. granorin, viridis, cauda bileta, letis ScniculiCque pedum nigris.

ViII. Ent. EUP. 1. p. 5 5 1 . n. S O ?

\ of it , I cannot be pofitive i I hal l therefore delcribe i t under the name of

Aphis avenz. Fab. Sp. In& i i . p. 386. n. 1 7 . Gmcl. tom. I. part. iv. p. 2206.

G p u i flavidum uti antennarum articulus primus. Om'; nigri. Abdomen obovatum

n. 52 .

caudi aculeatd. Ptdtv lividi, tarfis geniculilque nigris.

Habitat in tritiii et b c d i lpicis, avetiqup paniculis.

florets

florets ivliich produced this little plant ; but Come ears of a kind of beaided wheat, which I cultivated in my garden, were quite dif- coloured by it, without any larva attending upon it. Of all the inre& tha t are found in wheat, the lhrips phyjhpus, in all its kites, is by far the moit numerous. I do not recolle& examining a Gngle ear in which it was not to be found ; and my opinion itill remains unaltered, that it derives its nouriihment from the grain ; nor can I look upon the fpecies of this genus as carnivorous, any '

more than thofe which belong to its neighbouring genera, Aphis, Chcrmes, and Coccus.

I have nothing further a t this time to add upon this intereiting fubjea, and therefore believe me, &c.

XXI. Account