SCIENCE-GOSSIP. 



3*5 



NATURAL HISTORY AT PENARTH. 



T*HE Penarth Entomological and Natural 

 History Society met for tea, at their chair- 

 man's house, on Saturday, January 25th, after 

 which several of the members addressed the 

 meeting on various subjects. 



Mr. Geo. N. Dunn, M.K.C.S., gave an interesting 

 resume of the various accounts given of the so- 

 called new discovery by Professor Rontgen. Certain 

 rays of light or energy, emanating from a Crooke's 

 vacuum tube, lit by electricity, were found to pass 

 through bodies hitherto considered opaque. In 

 seeking for an explanation of his own want of 

 success Dr. Dunn found his apparatus to be quite 

 useless, and ascertained that the successful 

 operator, Mr. Swinton, had employed an apparatus 

 almost identical with that used by Nicola Telba, at 

 his epoch-making lecture, given at the Royal 

 Institution, February, 1892. 



Mr. A. H. Trow, B.Sc, gave a short account of 

 the "Material Basis of Heredity," illustrated by 

 microscope slides. He showed that the germ in all 

 cases, both of plants and animals, consisted of the 

 same component parts, viz., a cell of protoplasm, 

 in which a minute nucleus existed. These nuclei 

 in the animal closely resembled each other, until 

 the male and female germs combined, when the 

 apparent bundle of threads, which appeared to be 

 inextricably entangled, broke up into pairs of rods, 

 varying in number according to the species. From 

 these pairs evolved the offspring, usually partaking 

 of the characteristics of both parents ; but an 

 irregularity in this order of procedure would most 

 likely involve a turning back to the special 

 characteristics of earlier ancestors. The generation 

 of plants was more complex, there being frequently 

 an intermediate state. For instance, the spores 

 of ferns do not produce ferns, but a flat-lying 

 plant, from beneath which the ferns are finally 

 produced. 



Mr. C. W. Williams, the chairman, read some 

 notes .on Sirex gigas and S. juvencus, to settle a 

 doubtful point. These two insects are the only 

 ones in the tribe Xylophaga, which feed upon and 

 burrow in the wood of trees. The two species, 

 unlike the Phyllaphaga, which feed upon and 

 deposit their eggs in the softer portions of plants 

 cannot withdraw their ovipositors into the 

 abdomen, but they project in a most conspicuous 

 manner, obtaining for them, with country people, 

 the name of tail-wasps. The ovipositors consist of 

 two double-jointed plates, the second joint of each 

 being prolonged so as to form a sheath, within 

 which are these bristle-like organs, the upper being 

 the largest and channelled for the reception of the 

 two others, which together form an expansible 

 tube for the passage of the eggs. These three 



bristles are serrated. The larvae have remark- 

 ably powerful jaws, instances being known, 

 notably during the Crimean War, of their having 

 gnawed through lead. Sirex gigas is frequently 

 found in this country ; S. juvencus much more 

 rarely. There is a marked difference between 

 them. The female S. gigas has the thorax, 

 base of the abdomen below and a broad band 

 around it of deep black. The rest of the body and 

 the sides of the head are yellow. The thighs of 

 the hind legs and the bases of the others are also 

 black. The other legs and the antennae are yellow. 

 The abdomen is terminated by a straight, pointed 

 tail about five times as long as its diameter, with 

 the ovipositor beneath and projecting beyond it 

 about an equal length. The male is considerably 

 smaller and is black, except a broad yellow band 

 (four segments) around the middle of the abdomen. 

 5. juvencus, (female) is distinguished by its deep 

 metallic blue body. It has yellow legs, its pointed 

 abdomen closely resembles that of the male 

 S. gigas ; the ovipositor, however, is exactly similar 

 to that species. It is rarely recorded. Occasionally 

 it has obtained a footing for a short period in 

 England ; Mr. Drane, one of the Presidents of the 

 Penarth Society, having frequently taken it, when 

 a boy, near Llanberis Major. It does not appear 

 to thrive here. Sirex gigas, on the contrary, is 

 frequently captured, and a log of pine, cut down 

 at Southerndown, was recently exhibited, which 

 was honeycombed by this species. Mr. C. W. 

 Williams suggested a use for the horny "tail." 

 Entomologists must frequently have witnessed the 

 crane-fly ovipositing, standing upright on her hind 

 legs, and probing with her tail until a suitable 

 place is found, and then pausing a second to 

 deposit her egg. He believed observation of the 

 Sirices would reveal a similar process. The 

 ovipositor he assumed to be capable (its unique 

 attachment to the middle of the abdomen favour- 

 ing the idea) of being bent forward by the hinge- 

 like joint towards the thorax. Being thus out of 

 the way, the horn is brought into requisition by 

 the insect standing upon its hind legs, holding on 

 by its splendid claws, and feeling, with the ovipositor- 

 sheath, for a crevice or soft place in the trunk. 

 When that is discovered, the ovipositor is brought 

 back into position, the jointed plates turn aside to 

 right and left, and the boring proper, with the 

 united and flexible triple-edged saw, completed, 

 the insect now standing upon all its legs. The 

 tube is then expanded by the loosening of its 

 component parts, and the egg extruded. The hope 

 was expressed that the members would endeavour 

 to confirm, or otherwise, this suggestion, should 

 opportunity offer. 



