The Eggs of the Kerry Slug, Geomalacus maculosus, AllmanAuthor(s): Thomas RogersSource: The Irish Naturalist, Vol. 9, No. 7 (Jul., 1900), pp. 168-170Published by: Irish Naturalists' Journal Ltd.Stable URL: http://www.jstor.org/stable/25521793 .

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x68 The Irish Naturalist. [July,

THE EGGS OF THE KERRY SLUG, GEOMALACUS MACULOSUS, ALLMAN.

BY THOMAS ROGERS.

(PLATIE 5.)

THOUGH many naturalists have gone hunting for the Spotted

Slug in its native haunts, very few seem to have seen its eggs:

indeed, I know of only one published reference to them-that

quoted by Dr.Scharff in his "Slugs of Ireland,"' on the authority of Simroth, who states that Signor de Silva e Castro had seen

the eggs in Portugal, and that they were quite transparent.

In view of this, perhaps, the following observations on egg

clusters obtained many years ago by myself, and some lately

by Mr. R. Welch, may be of interest.

In August, I875, I received a Geornalacus from Kerry, and

placed it in a glass jar along with a little carrot, cabbage

leaves, and lettuce, which were renewed from time to time, occasionally washing out the jar with clean water. The

Geomalacuis seemed to keep in good condition and bright looking. In the August of the year following I found that it

had deposited eleven eggs of an oval fornm, about three

sixteenths of an inch long, which appeared to me very large for the size of the slug. The eggs were almost transparent, or opalescent. A month later, when cleaning out the jar, I

found that six of the eggs had assunmed a dark colour, due to the development of the pigment-cells of the young slugs; and soon afterwards I found that one of the younig slugs had been

hatched out, and began to creep about the body of the parent. The two remaining eggs had becomle quite dull, with no

apparent vitality in them, and in one I observed a small

worm-like entozoon working round the inside of the inner

wall of the egg. Another egg-case had collapsed from some cause. All the young that were hatched out were kept during the following winter, except that now and then one or two

were missing.

On the 30th of May, I877, the jar was examined, and I found that all the young slugs, except one, had disappeared; this one I placed in a separate jar, but it ultimately died. I came to the conclusion that the y(oung slugs had been eaten by their parent. From the young slug that had been separated

from the mother slug I took out the internal shell. I Transactions of the Royal Dublin Society, I89I, p 553.

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19c.] ROGERS.-- The Eggs of the Kerry Slug. i69

On the 29th July followinlg T noticed that the Geomalatus

had deposited fourteen more eggs, which were slightly adhering to each other by mucus. These were removed

into another jar, and kept separate from the parent slug. On

20th August eight more eggs were deposited, and placed in a separate jar, as I was anxious to raise a few adults. The eggs which were laid at the end of July were examined on

October I 2th, and I found that seven slugs were then grown to

about half to three-quarters of an inch long; one egg had

collapsed; what became of the others I canInot tell.

The eggs deposited on August 20th had not been hatched

when I looked at themii on October I2th, but by the end of the

month they were all hatched, except one, which appeared to

be dead. These young slugs increased in size until the

beginning of February, i878 (having beeil fed with carrot); two of them were then found dead, and very much attenuated.

The odontophores of these were found to have the same

characters as those of adults.

Of the slugs hatched from the eggs deposited at the end of July previously, I found one dead on the 20th of February,

i878. Thinking that they died for want of aninial food, I

cut an earthworm in three pieces, and placed it in the jar with four or five Zoni/es nitidulus. On clearing out the jar on March I7th, 1878, I found that the young slugs had

begun to diminiish in size and number, only two nmoderately healthy ones remiiainilng, and another much reduced in size,

with its head eaten off and the internal shell exposed; of the others [ could not find a trace. The earthworm had not

been eaten, the head and tail divisions of the wormn were still

alive, but the centre part was dead. I also found that one of the Zoniles had a hole through its shell, and the latter was enipty. On the i7th March I examined the jar in which were

placed the first batch of eggs which I had separated from the parent, and found all the young slugs dead, except two. The

discovery of four internal shells of the others leads me to put down their disappearance to cannibalism.

On July igth1 1878, the parent slug was found dead, but from what cause I could not determinle. It miglht have been

through old age. want of proper food, or excessive heat of the month (the latter most probably). The young slugs see.med

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170 7he Irish Naturalist. [July,

to die when they attained the length of about half or three

quarters of an inch. I did not know their proper food, and

perhaps I ought to have attended oftener to the cleaning out

of the jars with fresh water.

Mr. R. Welch informs me that, while ini the Kenmare district

in May, I898, assisting in the arrangements for the Field

Club Union Conference held there two months later, he.

collected a large number of Geomalac-cs, some of which he fed

well oni lichens ahd lettuce, to show at the winter meetings in

Belfast and Dublin. On July 22nd one of the slugs .laid

eighteen eggs in a cluster, partly eatinig three before he had

time to remove them, and on the 25th three more were laid.

These were loose, not attached. About a week later the eggs

had turned quite brown, and had shrivelled up to half their

size, so he placed them in weak alcohol for preservation.

During an Easter visit to the same district last year, Mr.

Arthur W. Stelfox kindly collected for hin. some more

specimens near the tunnel on the Olengarriff toad. These

were larger and much darker in colour than those previously

obtained in more sheltered positions at about goo feet less

altitude. On July 20th the largest specimen (40 mm. long

when at rest, 17 mm. wide, I5 mm. high) laid twenty-seven

eggs, twenty-four in a cluster and three free; the cluster

measured 3I by i6 by I4 mnl. ; the eggs were fairly uniform

in size, the largest 8j by 44 mm., the smallest 6 by 4 mm.

They varied slightly also in shape, some being almost ovoid,

but the miajority distinctly tapered at one end, not unlike the

shape of a Guillemot's egg. No attempt was made to hatch

these; they were promptly distributed to friends who had

never seen them. These Geomalacus egg-clusters are very

beautiful objects, as the photograph (Plate 5) of the last lot

Mr. Welch obtained will partly show. They are translucent,

with a pearly opalescence which it is impossible to render

properly in monochrome, if, indeed, at all.

The Irish specimens are certainly not transparent like

those reported from Portugal by Simrotli (loc. cit.); trans lucent, with a small transparent area at the narrower end in

some cases, would better describe them. Manchester.

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