170 



HARDWICKE'S SCIENCE-GOSSIP. 



contents of the tubes become exhausted ; greasy 

 substances smeared over the abdomen, blocking the 

 apertures and preventing respiration, result in suffo- 

 cation and consequent death. In the chrysalid, respi- 

 ration is reduced to a passive condition, but it 

 exists ; a pupa dipped in oil is destroyed. 



It is possible that sounds produced by insects 

 during flight do not entirely emanate from the 

 vibration of the wings, or exterrial frictions, but may 

 have some connection with the velocity of the air 

 streaming through the spiracles in and out of the 

 body. It is obvious that any unusual hum of an insect, 

 the unmistakable sound of an angry bee, or fitful 

 buzz of a blow-fly, cannot altogether proceed from a 

 sudden and abrupt alteration in the motion of the 

 wings, but is more likely to be the result of a rush 

 of respiration under strong excitement through the 

 trumpet-like orifices. 



Curious and strange conditions exist : among others 

 the larva of the Ichneumon, parasitic and buried in 

 the. tissues of a caterpillar, breathes through stigmata 

 differing but little from the larvae of other hymenop- 

 teraj they must necessarily tax the respiration of 

 their host (and it has been observed) by piercing a 

 tracheal tube and inspiring the air pouring from it. 

 Such a wound might not be vitally material to the 

 victim, as the puncture of the smallest branch would 

 amply sustain so minute a life as the larva of an 

 Ichneumon ; caterpillars so affected are always 

 sickly. 



Aquatic insects, both in the larval and perfect 

 condition, have varied, and curious modifications for 

 respiratory purposes, membranes perforated with 

 holes, prolonged gill-like flaps, in which the tracheal 

 tubes open out and radiate into minute fibrillar. In 

 the larva of the day-fly, common in every pond, a 

 most complicated organ is seen, a pronged brush- 

 like tail ; each filament is the termination of a tracheal 

 process. In other aquatic larvce may be found a 

 funnel or coronal of hairy plumes capable of gather- 

 ing from the surface of the water a globule of air and 

 carrying the supply for respiration into the depths. 

 The common pond-beetle (Dytiscus) rises to the 

 surface and entangles air between the elytra and 

 abdomen, where the spiracles are placed ; when the 

 captured store is exhausted, it returns for a renewal. 

 Another large aquatic insect [HydroKspiceus) collects 

 and sweeps in air with antennce covered with fine 

 hairs, packing and storing the minute bubbles under 

 the thorax, which is coated with a silky pubescence, 

 until there is accumulated a globule, often so large 

 and buoyant as to make it difficult for the creature 

 to sink to its home ; they may be seen with their 

 treasure cautiously creeping down the stems of plants. 

 Water-spiders (although not in the category of 

 insect life) excel all aquatic creatures in their 

 respiratory resources ; collecting air from the 

 surface, they carry it down by degrees to their 

 lairs, and, entangled in their webs, accumulate 



bubbles of considerable magnitude in which they 

 reside. The arachnida, in all that concerns their 

 condition of existence, exhibit resources, if not 

 approaching sagacity, at least amazing powers of 

 expedience. 



For dissection, and the exhibition of the tracheal 

 tubes and spiracles, a full-grown caterpillar, the 

 larva of a goat moth, may be selected, and the entire 

 system revealed. Pinned to a small plate of wax, 

 pressed on the bottom of a porcelain or glass tray 

 under water, an incision is made from end to end, the 

 integuments carefully turned back and pinned down ; 

 with a sable brush, a pair of fine surgical scissors 

 and a thick needle sharpened into a cutting edge, the 

 respiratory organs may be traced and washed out, the 

 tubes and spiracles removed, and the various parts 

 prepared as permanent objects, by easy and well- 

 known methods. 



Considered from a microscopist's point of view, 

 the insect world is endless ; many of the class 

 could creep through a pin-hole, possessing every 

 function of a highly organised life, with respira- 

 tory machinery no less complicated than in the 

 giants of the order. Dr. Carpenter says, " the 

 inexhaustibility of Nature is constantly becoming 

 more and more apparent, so that no apprehension 

 need arise that the microscopists' researches can ever 

 be brought to a standstill for want of an object," 

 and it may be added, the subject of a drawing. 



Crouch End. 



NOTES ON THE FERNS OF THE 

 PYRENEES. 



DURING a visit of some five weeks' duration to 

 the Pyrenees last autumn, I succeeded in 

 finding the following species of ferns, twenty-nine in 

 number — 



Cystopicris fragilis, C. alpina, C. montana, Adian- 

 turn Capillns- Veneris, Cheilanthes fragrans, Allosorus 

 crispus, Blcchnuvi Spicant, Aspleninm viride, A. 

 trichomanes, A. fontanum, A. Adiatitum-nigntm, 

 A. ruta-muraria, A. septentrionalc, A. Germaniatm, 

 Athyriiun filix-fccvmia, Pteris aquilina, Ceterach 

 qfficinaru?n, Scolopendrlnm vulgare, PolysticJntm 

 Lonchitis, P. aadeatwn, Lastraa filix-mas, L. oreop' 

 tcris, L. dilatata, Polypodiitin vnlgare, P. Phcgoptcris, 

 P. Dtyopteris, P. Robertiannvi, Osiminda regalis and 

 Botrychmni hinaria. 



I found several plants of Cystopteris alpina at the 

 Cirque of Gavarnie, where C, t?ioniana occurs as 

 well, the latter flourishing under some large rocks on 

 the left bank of the stream, near the wooden bridge 

 two or three hundred yards above the little hotel. 



P. Lonchitis, too, grows luxuriantly in the locality, 

 and a few plants of the moonwort, very dwarfed and 

 scanty, were just beginning to make their appearance 

 at the time of my visit. 



