June 1, 1866.] 



SCIENCE-GOSSIP. 



133 



BIDDULPHIA AND ISTHMIA. 



rTIHESE two genera of British diatoms are asso- 

 -*- ciated together in a group named Biddulphietc, 

 which might almost be termed the Royal Family of 

 diatoms. 



Fig. 131. Biddulphia pulchella x 400. 



Fig. 132. Isthmia enervis x 400. 



Biddulphia is characterized as having the valve 

 roundish or elliptical, frequently constricted. Frus- 

 tule compressed, quadrilateral, the corners produced 

 into rounded or horn-like processes, and the ends 

 generally bearing spines. The frustules united into a 

 continuous or zigzag filament. The species selected 

 for illustration (fig. 131) is Biddulphia pulchella. 



Isthmia has the valve elliptical, frustulc com- 

 pressed, trapezoidal, the lower angle of each 

 frustule attached by a small gelatinous cushion to 

 the one beneath, the whole forming an irregularly 

 branched filament. Of the two British species our 

 figure (fig. 132) represents Isthmia enervis. 



AN ARMY OF CATEBPILLABS. 



TTEARING on the 8th of May, from a farmer, 

 -*-*- a curious story about a "fall of worms" 

 in his neighbourhood, which caused some excite- 

 ment, I visited the ground, and found the field 

 crossed by a zigzag black line, about a yard hi 

 breadth, giving it the appearance at a distance as 

 if a cart had passed through it from which soot had 

 been thrown out in shovelfuls. The caterpillars 

 were not in motion, nor feeding, but basking in the 

 suu, rolled together in thick and deep lumps. I took 

 up about fifty of them by simply putting down my 

 hand. The owner of the land informed me that they 

 had appeared " suddenly," at five o'clock in the 

 morning, on the 2Sth of April, and that they were 

 then ten times thicker than I saw them, lying just 

 as if they had been emptied out "from pots or 

 bushels." Allowing something for rustic exaggera- 

 tion, this cannot have been far from the truth ; for 

 when I saw them, more than a week after, there were 

 signs of constant dispersion, as I found another body 

 in rapid march across the road adjoining the field, 

 while those remaining were certainly, when I saw 

 them, lying as if they had been emptied out from 

 breakfast-cups at intervals of a few inches. These 

 had moved, on the whole, a distance of two fields 

 from that in which they were first seen. None had 

 ever been observed in the neighbourhood before. 

 From rough estimates I have made since, I think I 

 am within the mark in saying there were at least a 

 million in the remnant I saw in the fields, though I 

 am well aware that this, to some people, may seem 

 almost incredible. I should be glad to know if this 

 is an unusual phenomenon, and how to account for 

 the sudden appearance of such an army. I have 

 never seen or heard of anything at all resembling it. 

 I need scarcely add that the aborigines were greatly 

 terrified, and seemed divided in opinion as to 

 whether it portended war or only cholera. — S. Leslie 

 Brakey, Ennis, Co. Clare, Ireland. 



Fig. 133. 



[The caterpillars received were those of the 

 " Greas y UTritillary"^ (Meliteea artemis), a local 

 species,| feeding on tne Scabious. One of these we 

 have engraved (fig. 133) from a specimen forwai'ded 

 by our correspondent.— 2ft/ ] 



