And not only the Off-spring of the Phalæna-Tribe, but there are some of the Ichneumon-Fly Kind also, endowed with this textrine Art. Of these I have met with two Sorts; one that spun a Milk-white, long, round, silken Web, as big as the top of ones Fingers, not hollow within, as many are, but filled throughout with Silk. These are woven round Bents, Stalks of Ribwort, &c. in Meadows. The other is a lump of many yellow, silken Cases, sticking confusedly together on Posts, under Cole-worts, &c. These Webs contain in them, small, whitish Maggots; which turn to a small, black, Ichneumon-Fly, with long, capillary Antennæ; Tan-coloured Legs; long Wings reaching beyond their Body, with a black Spot near the middle; the Alvus, like an Heart; and in some, a small setaceous Tail. Some of these Flies were of a shining, beautiful green Colour. I could not perceive any Difference, at least, not specifical, between the Flies coming from those two Productions.
[x] I have often admired how Wasps, Hornets, Ichneumon-Wasps, and other Insects that gather dry Materials for building their Nests, have found a proper matter to cement and glue their Combs, and line their Cells; which we find always sufficiently context and firm. But in all Probability, this useful Material is in their own Bodies; as ’tis in the Tinea vestivora, the Cadew Worm, and divers others. Goedart observes of his Eruca, Num. xx. 6. that fed upon Sallow-Leaves, that it made its Cell of the comminuted Leaves, glued together with its own Spittle, hæc pulveris aut arenæ instar comminuit, ac pituitoso quodam sui corporis succo ita maceravit, ut inde accommodatum subeundæ mutationi instanti locum sibi extruxerit. Domuncula hæc à communi Salicum ligno nihil differre videbatur, nisi quòd longè esset durior, adeò ut cultro vix disrumpi posset.
[y] An ingenious Gentlewoman of my Acquaintance, Wife to a learned Physician, taking much Pleasure to keep Silk-Worms, had once the Curiosity to draw out one of the oval Cases, which the Silk-Worm spins——into all the Silken Wire it was made up of, which, to the great Wonder as well of her Husband, as her self,——appeared to be, by measure, a great deal above 300 Yards, and yet weighed but two Grains and an half. Boyl Subtil. of Effluv. ch. 2.
[z] Since my penning this, I have met with the most sagacious Malpighi’s Account of Galls, &c. and find his Descriptions to be exceedingly accurate and true, having traced my self many of the Productions he hath mentioned. But I find Italy and Sicily (his Book de Gallis being published long after he was made Professor of Messina) more luxuriant in such Productions than England, at least, than the Parts about Upminster (where I live) are. For many, if not most of those about us, are taken Notice of by him, and several others besides that I never met with; although I have for many Years as critically observed all the Excrescences, and other morbid Tumors of Vegetables, as is almost possible, and do believe that few of them have escaped me.
As to the Method how those Galls and Balls are produced, the most simple, and consequently the most easy to be accounted for, is that in the Gems of Oak, which may be called Squamous-Oak-Cones, Capitula squamata, in Malpighi: Whose Description not exactly answering our English-Cones in divers Respects, I shall therefore pass his by, and shew only what I have observed my self concerning them.
These Cones are, in outward Appearance, perfectly like the Gems, only vastly bigger; and indeed they are no other than the Gems, encreased in Bigness, which naturally ought to be pushed out in Length: The Cause of which Obstruction of the Vegetation is this: Into the very Heart of the young tender Gem or Bud (which begins to be turgid in June, and to shoot towards the latter end of that Month, or beginning of the next; into this, I say) the Parent-Insect thrusts one or more Eggs, and not perhaps without some venomous Ichor therewith. This Egg soon becomes a Maggot, which eats it self a little Cell in the very Heart or Pith of the Gem, which is the Rudiment of the Branch, together with its Leaves and Fruit, as shall be hereafter shewn. The Branch being thus wholly destroyed, or at least its Vegetation being obstructed, the Sap that was to nourish it, is diverted to the remaining Parts of the Bud, which are only the scaly Teguments; which by these Means grow large and flourishing, and become a Covering to the Insect-Case, as before they were to the tender Branch and its Appendage.
The Case lying within this Cone, is at first but small, as the Maggot included in it is, but by degrees, as the Maggot increaseth, so it grows bigger, to about the Size of a large white Pease, long and round, resembling the Shape of a small Acorn.
The Insect it self, is (according to the modern Insectologers) of the Ichneumon-Fly Kind; with four Membranaceous Wings, reaching a little beyond the Body, articulated Horns, a large Thorax, bigger than the Belly; the Belly short and conical; much like the Heart of Animals: The Legs partly whitish, partly black. The Length of the Body from Head to Tail, about ²⁄₁₀ of an Inch; its Colour, a very beautiful shining Green, in some tending to a dark Copper-Colour. Figures both of the Cones, Cases, and Insects, may be seen among Malpighi’s Cuts of Galls, Tab. 13. and Tab. 20. Fig. 72. which Fig. 72. exhibits well enough some others of the Gall-Insects, but its Thorax is somewhat too short for ours.
[aa] Not only the Willow, and some other Trees, but Plants also, as Nettles, Ground-Ivy, &c. have Cases produced on their Leaves, by the Injection of the Eggs of an Ichneumon-Fly. I have observed those Cases always to grow in, or adjoining to some Rib of the Leaf, and their Production I conceive to be thus, viz. The Parent-Insect, with its stiff setaceous Tail, terebrates the Rib of the Leaf, when tender, and makes Way for its Egg into the very Pith or Heart thereof, and probably lays in therewith, some proper Juice of its Body, to pervert the regular Vegetation of it. From this Wound arises a small Excrescence, which (when the Egg is hatched into a Maggot) grows bigger and bigger, as the Maggot increases, swelling on each Side the Leaf between the two Membranes, and extending it self into the parenchymous Part thereof, until it is grown as big as two Grains of Wheat. In this Case lies a small, white, rough Maggot, which turns to an Aurelia, and afterwards to a very beautiful green, small Ichneumon-Fly.
[bb] What I suspected my self, I find confirmed by Malpighi, who in his exact and true Description of the Fly bred in the Oaken Galls, saith, Non sat fuit naturæ tam miro artificio Terebram seu Limam condidisse; sed inflicto vulnere, vel excitato foramine infundendum exinde liquorem intra Terebram condidit: quare fractâ per transversam muscarum terebrâ frequentissimè, vivente animali, guttæ aliquot diaphani humoris effluunt. And a little after, he confirms, by ocular Observation, what he imagin’d before, viz. Semel prope Junii finem vidi Muscam, qualem superiùs delineavi, insidentum quercinæ gemmæ, adhuc germinanti; hærebat etenim foliola stabili ab apice hiantis gemmæ erumpenti; & convulso in arcum corpore, terebram evaginabat, ipsamque sensam immittebat; & tumefacto ventre circa terebræ radicem tumorem excitabat, quem interpolatis vicibus remittebat. In folio igitur, avulsà Muscâ, minima & diaphana reperii ejecta ova, simillima iis, quæ adhuc in tubis supererant. Non licuit iterum idem admirari spectaculum, &c.