388 DR. J. B. HICKS ON THE ORGANS 
In some of the Lamellicorns the closing-in membrane is prolonged to a point, sometimes 
rigid, so as to be easily mistaken for a hair; but closer inspection and comparison, I am 
sure, will satisfy any one as to its true nature. I can best explain what I mean, by the 
antenna of Geotrupes stercorarius. The surface of the lamellæ is patterned all over in 
the same parts as in the former Lamellicorns, and in a very similar manner to those of 
Andrena fulva, shown in fig. 8 of my former paper. The surface is occupied with about an 
equal number of true hairs, and articulated projections very like hairs (I. fig. 20), beneath 
each of which is a sac, as in the former kind of antennze; and as the sac does not extend 
through the whole thickness of the antenna-wall, there is, as in Dynastes, a tubular com- 
munication with the interior of the lamella. (See I. figs. 1, 2.) 
This structure will help to explain other forms in the Lamellicorn groups, as for 
instance in the Stag Beetle (Lucanus Cervus). Over the same parts as in the others 
are a number of apparent hairs, slightly curved, projecting from the antenna-wall. On 
looking more closely, it will be observed that they are not all true hairs; on the contrary, 
only a few of the larger ones are hairs, while beneath the rest an elongated sac is placed, 
as is shown at K. figs. 1, 2. In this insect the terminal lamella has a large cavity— 
sometimes there are two—extending deeply into its interior (fig.3). The diameter of the 
sac is 5555 inch. 
A similar condition exists in Hydrophilus piceus ; but the nature of the sacs is well shown 
by the fact that some have the closing-in membrane level, and others slightly raised, whilst 
some have it prolonged into a spine (G. fig. 2). The diameters range from teso to 
3760 inch. This peculiar-shaped antenna has nine joints; the last three are liberally 
furnished with these sacs, and of a larger size than any I have hitherto found: possibly 
the size of the insect will account for it, though it may generally be said that the size of 
the insect has but slight relation to the size of the sacs, as will be seen by comparing 
the various measurements I have given. | | 
That these sacs with hair-like apices are the same as those which are found in Melolontha, 
Dynastes, &c. is evident from the facts—1st, that they are situated in the same position; 
2nd, that some have level, others spinous apices on the same antenna; 8rd, so far as I have 
found on examination of a large number of insects, I think it may be laid down as a rule, 
that no cuticular projection or spine has a cavity or sac beneath it in any other part of the 
insect, except in the antennæ. In some Hemiptera I have found beneath the true hairs a 
cavity, but not like these sacs, inasmuch as the whole antenna-wall was protruded, with a 
true hair at the apex. m 
= are ee of the covering-in membrane is an important point, because : 
© - : tese with what is generally understood to be the structure z 
od us when we consider the habit of Hydrophilus and compare : 
may obtain a clue as to the ete — sa stp a 
Hint aril) ba: soen-thot = wa of these organs in the antennæ. If watched a er 
moment he is placed in wat ë h Rae es Je release t 
VEN mar = : — brings them beneath the joint of thé head = 
the under surface a the tho ges maner: by the silvery film of air which we 
rax, and which is collected by the numerous downy hairs 0? 
