Part 10

Let us now consider how the intestinal canal is circumstanced in the two sections into which the Class _Arachnida_ is divided; the _Scorpionidea_, and _Araneidea_. In the Scorpions, this organ proceeds from the mouth to the anus without any flexure or convolution, so that its length is scarcely equal to that of the body[568]; it is slender, and its diameter, with the exception of an irregular dilatation here and there, is nearly the same in its whole extent; the gullet is short; the stomach long, and nearly cylindrical; the _duodenum_ shorter and thicker than the stomach, from which, as well as from the _rectum_, it is separated by a valve; the latter is cylindrical, and opens at the anus above the insertion of the vesicle that secretes the poison[569]. With regard to the _biliary_ system and its organs: The _liver_ is of a pulpy granular consistence and of a brownish colour, fills the whole cavity of the trunk and abdomen, and serves as a bed for the other intestines. It is divided longitudinally into two portions, by the channel in which the heart reposes--its anterior part is formed into many irregular lobes, by the sinuosities of the trunk; at the other extremity, it terminates in two acute ends, which enter the first joint of the tail; its surface presents a reticular appearance, the result of the approximation of polygonous _lobuli_; its interior is a tissue of infinitely minute glands: in _Scorpio occitanus_ there are about forty pyramidal _lobuli_ detached from each other, the summits of which, by their union, form bunches that have their excretory canals, varying in number in different species, which convey the bile to the alimentary tube; in the above insect there are six pairs, three in the trunk and three in the abdomen, and in _S. Europæus_ a smaller number[570]; these vessels run transversely from the liver, or aggregation of conglomerate glands, to the intestinal canal[571]; the bunches consist of an infinite number of spherical glands, generally filled with a brown thick fluid[572]: besides the transverse vessels, from the base of the stomach there issue two pairs of very slender tortuous ones, seemingly analogous to the common bile-vessels; one pair of which runs upwards, one on each side that organ towards the mouth, forming here and there some ramifications which enter the liver; and the other runs nearly transversely to it[573]. As the fluid contained in these vessels is different from that contained in the glands of the liver, M. Marcel de Serres supposes they may be chyliferous[574].

In the _Araneidea_ also the alimentary canal is nearly straight, and scarcely exceeds the length of the body: the _gullet_ is rather thick and cylindrical[575]; the _stomach_ is distinguished anteriorly by two pairs of sacs, the upper pair being much the largest and nearly triangular, the lower linear[576]; from these sacs a narrow tube runs towards the _rectum_, but which is so entangled with the liver, muscles, &c., as not to be easily made out[577]; the _rectum_ is rather tumid, and has a lateral _cœcum_[578]. The disposition of the liver or conglomerate glands is stated to be similar to that of the scorpion[579]; it is usually white, but in some species it is yellowish, or reddish, and its lower surface has sometimes regular excavations[580]; no transverse hepatic ducts connecting it with the alimentary canal, as in the scorpion, appear to have been at present discovered: two pairs of capillary _free_ vessels are attached to the base of the _rectum_ on one side, which, except in their situation, seem analogous to the bile-vessels of insects[581].

From the above detailed account of the alimentary canal of the animals whose internal anatomy we are considering, it appears that M. Cuvier's observation--that the length and complication of the intestines indicate a less substantial kind of nutriment--does not hold universally: thus, in _Necrophorus_ and _Silpha_, _carnivorous_ insects, the intestinal canal in its length and convolutions exceeds those of most _herbivorous_ ones, and in _Cassida viridis_ and some others of the _latter_ tribe are not longer than those of the _predaceous_ beetles. In _herbivorous larvæ_ also, in general, the length of the alimentary canal does not exceed that of the body, but in those of some _flesh_-flies (_Musca vomitoria_) it very greatly exceeds it[582]. So true is the observation--that there is no general rule without exceptions.

In this letter it may not be out of place to say a few words upon the _excrements_ of insects; which, strange as the observation may seem, but it is no less true than strange, are sometimes pleasing to the eye, from their symmetry, and to the taste, from their sweetness. In those that masticate their food they are solid, and in those that take it by suction, fluid or semi-fluid. In the caterpillars of _Lepidoptera_ they are of the former description, and every grain wears some resemblance to an insect's egg: as the passage in many of these consists of _six_ fleshy parts separated by channels, so the excrement represents six little prisms separated by six channels[583]. The _Aphides_ all secrete a fluid excrement as sweet as honey, of which the ants are so fond[584], which is ejected not only at the anal passage, but, in many, by two little siphonets also above it[585]. A semi-fluid excrement is produced by some species of _Chermes_, as that which inhabits the Box, which often comes from the animal in long convoluted strings resembling vermicelli. Reaumur says its taste is agreeable, much more so than that of manna[586]. Under this head should be included the abundant spume with which the larva of _Cercopis spumaria_ envelopes itself[587].

I am, &c.

FOOTNOTES:

[418] _Anat. Comp._ iv. 129.

[419] Cuv. _Anat. Comp._ iv. 129.

[420] PLATE XXI. FIG. 3. c, d, e, is the intestinal canal of the larva of the _Cossus_.

[421] Cuv. _Ibid._ 112.

[422] Ramdohr _Anat. der Ins._ 6.

[423] _Ibid._ 25.

[424] _Ibid._ 6.

[425] Cuv. _ubi supr._ 113.

[426] Comp. Ramdohr _Anat._ 7.

[427] PLATE XXI. FIG. 3. _c._

[428] _Tenebrio_ Ramdohr, _ubi supr._ 9. _t._ iv. _f._ 1.

[429] _Agrion._ _Ibid._ _t._ xv. _f._ 4. _a, b._

[430] _Ibid._

[431] Many other insects that live by suction have something similar, as the honey-bag of butterflies, PLATE XXX. FIG. 10, 11. _a._ Ramdohr _t._ xviii. _f._ 2. with _t._ xix. _f._ 1-3. and xxi. 1, 3, &c.

[432] Ramdohr _Anat._ 11--.

[433] PLATE XXI. FIG. 3. _d._

[434] Ramdohr _Ibid._ 28--.

[435] Herold (_Schmetterl._ 24) says that Ramdohr is mistaken here, and denies the existence of this juice in insects; but as Ramdohr's researches were so widely extended, he is most likely to be right.

[436] Ramdohr _Ibid._ 29.

[437] _Ibid._ 31.

[438] _Ibid._ 28.

[439] _Anat. Comp._ iv. 135. Comp. Dr. Kidd in _Philos. Trans._ 1825. 223. _t._ xv. _f._ 6, 7.

[440] Ramdohr _Anat._ 15.

[441] _Ibid._ 15.

[442] _Ibid._ 18.

[443] _Ibid._

[444] _Ibid._

[445] Swamm. _Bibl. Nat._ i. 94. b. Cuv. _Anat. Comp._ iv. 134.

[446] _Ubi supr._ 18.

[447] _Ibid._ _t._ i. _f._ 1. _e._ 5. _c._ 9. _g, h._

[448] _Ibid._ _t._ xxv. _f._ 4. _bb._

[449] Ramdohr _Anat._ _t._ viii. _f._ 3. _cc._

[450] _Ibid._ _t._ vii. _f._ 2.

[451] _Ibid._ 20.

[452] _Anat. Comp._ iv. 132.

[453] _Ibid._ and 136.

[454] _Ubi supr._ 30.

[455] _Ibid._ 31. _t._ iv. _f._ 2. _c._ _t._ v. _f._ 1. _d. f._ 4. D.

[456] _Ibid._ 32.

[457] _Ibid._ 34.

[458] Ramdohr _Anat._ 35.

[459] _Ibid._ _t._ xxiv. _f._ 1. _F._

[460] _Ibid._ 36. _t._ vii. _f._ 2. _kk._ _t._ viii. _f._ 3. _g, hh._

[461] _Ibid._ _t._ xii. _f._ 1. _t._ xvii. _f._ 1. _t._ vii. _f._ 5.

[462] _Ibid._ 37.

[463] _Ibid._ 38.

[464] _Ibid._

[465] Ramdohr _Anat._ 40.

[466] _De Bombyc._ 18--.

[467] _Anat. Comp._ iv. 153.

[468] _Ibid._

[469] _Ibid._

[470] Ramdohr 43. _Cicindela campestris_, _t._ iii. _f._ 1. K.

[471] _Phryganea grandis_, _Ibid._ _t._ xvi. _f._ 2.

[472] _Notonecta glauca_, _Ibid._ _t._ xxiii. _f._ 5.

[473] Of _Musca vomitoria_, _Ibid._ _t._ xix. _f._ 5.

[474] _Ibid._ _t._ viii. _f._ 1. H. and G. _f._ 2.

[475] _Ibid._ 50.

[476] _Ibid._

[477] _Ibid._

[478] _Ibid._ 44. _t._ i. _f._ 9.

[479] _Ibid._

[480] _Ibid._ _t._ vi. _f._ 5. H.

[481] Kidd in _Philos. Trans._ 1825. _t._ xv. _f._ 6.

[482] _Ibid._ _t._ xix. _f._ 1. _N, N, O,_ _f._ 2. _P, P, O._

[483] _Ibid._ _t._ 1. _f._ 1. _kkk._

[484] Ramdohr, _t._ xiii. _f._ 1-3.

[485] _Ibid._ 44.

[486] _Ibid._ 45.

[487] _Ibid._ 45. PLATE XXI. FIG. 3. _f. f._

[488] Rhamdohr, _Ibid._ _t._ iii. _f._ 6. E.

[489] _Ibid._ _t._ i. _f._ 1. 5. 9. _t._ xiv. _f._ 1-3.

[490] _Ibid._ 46. _t._ vi. _f._ 3.

[491] Ramdohr, _t._ vii. _f._ 2.

[492] _Ibid._ _t._ ii. iii. &c. _t._ xx. _f._ 1, 2. 6. _t._ xxii. _f._ 1-5. &c.

[493] _Ibid._ _t._ xviii. _f._ 1. 5. _t._ iv. _f._ 1. See also _t._ vi. _f._ 1. 3.

[494] _Ibid._ _Anat._ _t._ xvii. _f._ 1, 2. 6.

[495] _Ibid._ _t._ xiv. _f._ 3.

[496] _Ibid._ _t._ xiii. _f._ 4.

[497] _Ibid._ _t._ xv. _f._ 3, 4. _t._ 1. _f._ 1. 5. 9. _t._ xii. _f._ 4, 5, 6, &c.

[498] _Ibid._ _t._ xi. _f._ 4. _t._ xii. _f._ 4-6. _t._ xiii. _f._ 2-4, &c.

[499] _Ibid._ _t._ vii. _f._ 1. _t._ viii. _f._ 1, &c.

[500] Ramdohr _Anat._ _t._ ii. iii. xxv.

[501] _Ibid._ _t._ iii. _f._ 6. _t._ iv. _f._ 2. _t._ v. _f._ 1.

[502] _Ibid._ _f._ l. _e. f._ 3.

[503] _Ibid._ 122.

[504] _Ibid._ 123.

[505] _Ibid._ _t._ v. _f._ 4. B.

[506] _Ibid._ 94.

[507] _Ibid._ 96--.

[508] Ramdohr _t._ x. _f._ 1. 8.

[509] _Ibid._ _f._ 8. _b. c._

[510] _Ibid._ 98. _t._ x. _f._ 2-4. From Ramdohr's figure, compared with the size of the insect, it appears that the gizzard could scarcely have been of greater diameter.

[511] _Ibid._ _f._ 2.

[512] See W. Curtis in _Linn. Trans._ i. 88.

[513] Ramdohr _t._ x. _f._ 1. _d._

[514] _Ibid._ _l l._

[515] _Ibid._ _t._ ix. _f._ 1, 2. _t._ xi. _f._ 3. _t._ xxiv. _f._ 1, 2.

[516] Ramdohr 103.

[517] _Ibid._ 104. _t._ vi. _f._ 4. D.

[518] _Ibid._ _f._ 2. B.

[519] _Ibid._ _t._ vi. _f._ 3. E.

[520] _Ibid._ 101.

[521] _Ibid._ _t._ i. _f._ 1. 5. 9.

[522] _Ibid._ _f._ 2, 3, 4. 7, 8. 12.

[523] _Ibid._ _f._ 1. _e,_ _f._ 5. _c._ _f._ 9. _g h._

[524] _Ibid._ _f._ 1. 9. _k._

[525] _Ibid._ _t._ xv. _f._ 3, 4. _t._ xvii. _f._ 2. 6.

[526] _Ibid._ _t._ xv. _f._ 3, 4, _f._

[527] _Ibid._ _t._ xvii. _f._ 2. _c._ _f._ 6. _d._

[528] _Ibid._ _f._ 2. _b._ _f._ 6. _c._

[529] Ramdohr _t._ xii. _f._ 6. _H._ _t._ xiii. _f._ 1. _f._

[530] _Ibid._ _t._ xiv. _f._ 2, 3, _C._

[531] _Ibid._ _t._ xii. _f._ 6. _D._ _t._ xiii. _f._ 1. _b._

[532] _Ibid._ 133. _t._ xii. _f._ 1-3.

[533] _Ibid._ _f._ 4.

[534] Comp. Ramdohr _t._ xxii. _f._ 3. _M._ FIG. 4. 3. with _t._ xxi. _f._ 1. _I._

[535] Ramdohr _t._ xxii. _f._ 1. c. _f._ 3, 4. _B_--.

[536] _Ibid._ _f._ 1. _D E._ _f._ 3. _C D._

[537] _Ibid._ _t._ xxii. _f._ 1. _D, E._ _f._ 3. _C, D._ _f._ 4. _C._

[538] _Ibid._ 198.

[539] _Ibid._ _t._ xxvi. _f._ 2. 4.

[540] _Ibid._ _t._ xxxiii. _f._ 3.

[541] Ramdohr _t._ xviii. _f._ 1. _F, G._

[542] _Ibid._ _L, K._

[543] PLATE XXX. FIG. 7.

[544] Ibid. FIG. 8.

[545] Ibid. FIG. 9.

[546] PLATE XXX. FIG. 10.

[547] Ibid. FIG. 11. _a._

[548] Ibid. _e._

[549] Ibid. _d._

[550] Ramdohr, _Ibid._ _t._ xx. _f._ 1. _E._ _f._ 6. _C._

[551] _Ibid._ _t._ xix. _f._ 2. _C._ _f._ 3. _CCD._ _t._ xx. _f._ 2. _E._

[552] _Ibid._ _t._ xix. _f._ 2. _D._

[553] _Ibid._ _t._ xx. _f._ 2. _FF._ _f._ 6. _DD._ 184. 180.--

[554] _Ibid._ _t._ xix. _f._ 1. _ON._ _f._ 2. _OP._ _f._ 3. _F._ _t._ xxviii. _f._ 1, 2. _p. q._

[555] Ramdohr, _Ibid._ _t._ xx. _f._ 1. _G._ _f._ 2, 3. _L._

[556] _Ibid._ _t._ xxi. _f._ 1. _D._

[557] _Ibid._ 172.

[558] _Ibid._ _t._ xix. _f._ 2. _K L._ This organ seems analogous to that with four retractile fleshy horns, observed by Reaumur and De Geer in other species of _Muscidæ_. Reaum. iv. _t._ xxviii. _f._ 13. _a, s._ De Geer vi. _t._ iii. _f._ 18. _c, d._

[559] Ramdohr _t._ xxi. _f._ 6.

[560] Ramdohr _t._ xxix. _f._ 1 *. _A._

[561] _Ibid._ and _f._ 3. _B, D._

[562] _Ibid._ _f._ 2, 3. 5. &c.

[563] See above, p. 99--.

[564] Treviranus and Ramdohr are of the former opinion; and Meckel, Cuvier, Marcel de Serres, and Leon du Four, of the latter.

[565] Treviran _Arachnid._ _t._ 1. _f._ 6. _v._

[566] _Ibid._ _n._

[567] _Ibid._ _t._ ii. _f._ 24. β.

[568] Treviran _Arachnid._ _f._ 6. _B B._

[569] _N. Dict. d'Hist. Nat._ xxx. 423--. Comp. Treviranus, _Arachnid._ _t._ i. _f._ 6.

[570] Treviranus, _Ibid._ _v._

[571] _N. Dict. d'Hist. Nat._ xxx. 421--. Comp. Treviran. _Ibid._

[572] _N. Dict. d'Hist. Nat._ _Ibid._

[573] Treviran. _Ibid._ _t._ i. _f._ 6. _i i, c c._

[574] _N. Dict. d'Hist. Nat._ _Ibid._

[575] Treviran. _Ibid._ _t._ ii. _f._ 24. _a._

[576] _Ibid._ _v, b._

[577] _Ibid._ _c, d, f._

[578] _Ibid._ _g, n._

[579] _N. Dict. d'Hist. Nat._ _Ibid._

[580] Treviran. _Ibid._ 28.

[581] _Ibid._ _t._ ii. _f._ 24. β.

[582] Ramdohr, _t._ xix. _f._ 1.

[583] Reaum. i. 143. _t._ v. _f._ 9.

[584] VOL. II. p. 88--.

[585] De Geer iii. 26.

[586] Reaum. iii. 357. _t._ xxix. _f._ 6-10.

[587] VOL. II. p. 225.

LETTER XLI.

_INTERNAL ANATOMY AND PHYSIOLOGY OF INSECTS, CONTINUED._

SECRETION.

Having given you so full an account of the system of _digestion_ in insects, I am now to say something concerning their _secretions_, and the organs by which they are elaborated. Though no individual amongst them perhaps secretes so many different substances as the warm-blooded animals; yet in general the Class abounds in secretions perhaps as numerous and extraordinary as in the last-mentioned tribes, to some of which a few of them are analogous, while others are altogether peculiar. We know little or nothing of the mode in which the process of secretion in insects is accomplished; in most cases we cannot even discover, except in general, whence the secreted substance originates; and in others, though we are able to trace the vessels that contain it, we are often in the dark as to their structure.--Cuvier, as has been before hinted, from not being able to detect any thing in them like _glands_, and from their being constantly bathed in the _blood_ or nutritive fluid, conceives that they separate the peculiar substances they contain, by imbibition or infiltration, through the pores of the skin[588]; a circumstance which seems to indicate a certain conformation of the pores both as to size and figure, so as to enable them to admit only one peculiar product.

In treating on this subject, I shall first consider the _organs_ of secretion, and next their _products_.

I. _Organs of Secretion._ In general, these are membranous vessels that float in the blood or nutritive fluid, and secrete from it a peculiar substance. They may be denominated according to their products--_Silk-secretors_, _Saliva-secretors_, _Varnish-secretor_, _Jelly_ or _Gluten-secretor_, _Poison-secretor_, and _Scent-secretors_.

i. _Silk-Secretors_ (_Sericteria_). These organs are most remarkable in the caterpillars of the _nocturnal Lepidoptera_ or moths, especially in that tribe called _Bombyces_, to which the silkworm belongs: but this faculty is not confined to these insects, but is shared by many other _larvæ_ in different Orders; and in one instance at least, by the _imago_. In general, the outlet of the silk-secretors is at the _mouth_; sometimes, however, as in the larva of _Myrmeleon_ and the imago of _Hydrophilus_, its exit is at the _anus_. The first is the organ which in the silk-worm provides for us that beautiful substance from which the animal takes its name. There are always _two_ of these vessels, which are long floating tubes, growing slender towards the head of the insect, where they unite to form the spinneret (_fusulus_) before described[589], which renders the silk. Their lower extremity also is commonly more slender than the middle, and is closed at the end. These organs are usually very much convoluted and twisted[590]. According to Ramdohr[591], they consist of two transparent membranes, between which is found a yellow or transparent jelly. The greater the quantity of silk employed by the caterpillar in the construction of its cocoon, &c., the longer are the silk-secretors. Those of the silkworm are a _foot_ long[592], while those of the larva of the goat-moth are little more than _three inches_[593].

Other insects spin silk with the _posterior_ extremity of their body. In the great water-beetle (_Hydrophilus piceus_) the anus is furnished with two spinnerets, with which it spins its egg-pouch[594]; these are in connexion, probably, with the five long and large vessels containing a green fluid, described by Cuvier[595], which surround the base of each branch of the ovaries. The larva of _Myrmeleon_, which also spins a cocoon with its anus, differs remarkably in this respect from other insects, since its reservoir for the matter of silk is the _rectum_; this is connected with a horny tube, which the animal can protrude, and thus agglutinate the silk and grains of sand that compose its cocoon[596].

The _web_ of spiders is also a kind of _silk_ remarkable for its lightness and extreme tenuity. It is spun from four anal spinnerets, which never vary in number; two longer organs peculiar to some species have been mistaken for additional ones, but Treviranus affirms that they are merely a kind of anal _feeler_. Their structure, as far as known, has been before described[597]. The web is secreted in vessels varying in form. In some (_Clubiona atrox_) they consist of two larger and two smaller ones, at the base of which lie many still more minute[598]. The four larger vessels are wide in the middle, branching at top, and below terminating in a narrow canal leading to the spinnerets[599]. Treviranus thinks the fluid contained in the lower minute vessels different from that furnished by the larger ones--but for what purpose it is employed has not been ascertained.

ii. _Saliva-secretors_ (_Sialisteria_). These are organs, rendering a fluid to the mouth or stomach, that are found in many insects, especially those that take their food by _suction_, as the _Hemiptera_, _Lepidoptera_, and _Diptera_, though they are not confined to the perfect insect, being also in some cases visible in the larva. Swammerdam was one of the first that discovered them, and he suspects that they may be _salival_ vessels; though he, as well as Ramdohr, thinks they are the same with the _silk_ vessels of the caterpillar[600]; an opinion which Herold has sufficiently disproved, by showing that at one period of the insect's life they co-exist[601], and Lyonet discovered a very conspicuous pair in the caterpillar of the Cossus, co-existent with the silk-secretors[602]. But the physiologist who has given the fullest account of these organs is Ramdohr:--I shall therefore extract chiefly from him what I have further to communicate with respect to them.

They are variously constructed blind vessels, that are present in almost all insects that take their food by _suction_, but are mostly wanting in those that _masticate_ it. They have been found, however, in _Cryptorhynchus Lapathi_, _Chrysopa Perla_, and _Iulus terrestris_. The most usual number of the saliva-secretors is _two_[603]; but sometimes, as in the first of the last-named insects, there is only _one_[604]; in others (_Pentatoma Baccarum_) there are _three_, the exterior one consisting of a pair of reservoirs connecting with the gullet by a single capillary tube[605]; in _Pentatoma prasina_ there appear to be _four_[606]; in _Nepa cinerea_, even _six_--the exterior double pair in this insect, under a powerful lens, is found to consist of spherical vesicles, resembling somewhat a bunch of currants[607]; and in _Syrphus arcuatus_ they are covered with _four_ rows of similar ones[608]. In the flea they consist of two pair of spherical reservoirs, each of which is connected with a short tube, which uniting with that of the other forms a common capillary one connecting with the mouth or gullet[609]; these organs sometimes terminate below in slender vessels;--thus, in _Nepa_, the inner pair terminates in a single vessel of this description[610], and in _Tabanus_ and _Hemerobius_ apparently in many[611]. It admits of a doubt however, as was lately observed, whether in the _Hemiptera_, which have usually more than a _pair_ of these organs, some are not rather _food-reservoirs_ as in the _Diptera_.

The saliva-secretors open either into the _instruments_ of _suction_ themselves (_Tabanus_, _Musca_); or into the entrance of the _gullet_ (_Pentatoma_, &c.); or, lastly, into that of the _stomach_ (_Syrphus_, _Bombylius_). Those which lie at the entrance of the _stomach_ consist only of a blind uniform _tube_[612]; but there is commonly to be distinguished in those that open into the _mouth_, a _reservoir_, varying in shape in different species, and terminating in a capillary tube, or tubes, at one or both extremities[613]. In Bugs, _two_ pair of these vessels are often present, one of which opens into the stomach (_Reduvius_), or gullet (_Pentatoma_), but the other into the instruments of suction[614]. In the _Diptera_ they open into the stomach when the insect feeds only upon the nectar of flowers (_Syrphus_), and into the proboscis when it feeds upon both animal and vegetable juices (_Tabanus_, _Musca_). The function of the fluid secreted by these organs is to moisten or dilute the food before it is received by the instruments of suction and passed to the stomach[615]. When a common house-fly applies its proboscis to a piece of sugar, it is easy to see that it moistens and dissolves it by some fluid.

iii. _Varnish-secretor_ (_Colleterium_). In butterflies, moths, and several other insects, one or more vessels called blind vessels open into the oviduct, concerning the use of which, physiologists are not agreed. In the cabbage butterfly there is a pair of ovate ones, or rather a bilobed one, each lobe of which externally terminates in long perplexed convolutions, not easily traced, filled with a yellow fluid, which Reaumur and Herold think is used for varnishing or gumming the eggs, so that they may adhere to the leaves on which they are deposited: it may probably serve likewise for other uses[616]. Another vessel is also to be found in the above butterfly, which enters the oviduct above this, filled with a thick white fluid, the function of which is, probably, to lubricate the passage[617]. A similar organ is found in _Phryganea grandis_[618].

iv. _Jelly-secretor_ (_Corysterium_). This is a remarkable organ, related to the preceding, which secretes the jelly of _Trichoptera_, some _Diptera_, &c.; this organ in the former, at least in _Phryganea grandis_, is of an irregular shape, with four horns or processes[619].