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BARDWICKE'S SCIENCE-GOSSIP. 



THE HISTORY OF RANATRA LINEARIS. 



ON the excursion of the Hackney Microscopical 

 and Natural History Society, held June 28, 

 I captured a pair of that interesting aquatic insect the 

 Ranatra linearis, and having since had the good 

 fortune to breed from them, I venture to submit to 

 you the following short observations. To watch 

 these insects feed, and their mode of taking their 

 food, I placed them in an upright glass aquarium 

 with plants of Vallisncrici spiralis and common frog- 

 bit— this was on June 28. On July 7, I was much 

 surprised to find the leaf of frog-bit exhibiting a 

 most unusual appearance — as shown in fig. 191. The 



Fig. 191. — Eggs deposited on leaf of Frog-bit. 



Fig. 132.— Single eggs and young of Ranatra. 



best verbal description I can give of this appearance is, 

 that the floating leaf appeared on the top to possess 

 the antennae of some moth, to which underneath was 

 attached a small substance, something in shape like 

 a canary-seed, but more rounded at the extremities, 

 especially at the end from which these antennae or ap- 

 panages sprung. The leaf had evidently been pierced, 

 the appanages thrust through when they opening 

 into a V-like shape, kept the underneath substance 

 from falling. I was much puzzled by these appear- 

 ances, and being quite ignorant of what they were, 

 called in one or two friends to see them, in the hope 

 of acquiring information ; but being unable to get 

 any I the more anxiously watched and almost came 

 to the conclusion that they were the germs of some 

 botanical production. The leaf of the frog-bit from 

 some cause or other decaying they gradually sank, the 

 same V-like appanage which had kept them in their 

 position now keeping them from falling too fast or 

 from sinking in the soft mud at the bottom of the 

 aquarium ; here they remained in a perpendicular 

 position and were watched from time to time. On 

 August 4, I was delighted to find four young Ranatra 

 swimming freely about (see fig. 192). They were about 

 half an inch in length, and in form so like the parents 

 it was impossible to be deceived. On the 5th another 

 was added to the number, which the elder ones 



instantly devoured while it was yet in a helpless' 

 condition. I should think the first must have been 

 hatched on August 3, although I did not see them 

 until the 4th, they were so strong and well-grown 

 when first observed, whereas the fifth, which must 

 have been seen directly after its development, was a 

 poor little pink thing with large black eyes, and soon 

 became a prey to those of yesterday. The appearance 

 of these young Ranatra led to the discovery that the 

 objects on leaf of the frog-bit which had so puzzled 

 me were the ova of this insect, for I found them all' 

 on the bottom of the aquarium quite empty, with an 

 opening in the end between the antennae or appan- 

 ages, so I come to the conclusion that when I took 



Fig. 193. — Full-grown Ranatra (natural size). 



the adult Ranatra on June 28, they were in copula- 

 tion, that the ova were deposited on July 6 or 7, and. 

 the puny insect developed on August 4 and 5.- 

 These times may of course vary according to circum- 

 stances, I only speak from personal observation. I 

 cannot help thinking what an interesting sight it 

 must have been to have watched the insect depositing 

 the ova, how the leaf must have been pierced, the 

 ova extruded, the antennae— if they may be so called 

 — being thrust through the perforated opening, on 

 which they must have immediately sprung into a 

 wedge-like shape — opening wide at the top — to keep 

 the ova in position. How long it takes the young 

 insect to acquire maturity I cannot say, probably 

 some twelvemonths ; unfortunately all mine perished,, 

 the greater part being devoured by their brethren,. 



