JUNE 10, 1915] 

NATURE 
399 

OLFACTORY STRUCTURES IN INSECTS. 
ate 2 is no doubt that many insects have a 
sense of smell, but there is great variety of 
opinion as to the precise location of the sense. 
Dr. N. E. McIndoo,! of the Washington Bureau 
of Entomology, has summed up the discrepant 
views in forty pages, and also in one word— 
“chaos.” Lehmann seems to have been the first 
to experiment (1799), and he was led to the con- 
clusion that the seat of smell is in the spiracles. 
Most of the older naturalists reached their con- 
clusion without experimenting, and the sense of 
smell has been referred to at least a dozen 
different parts, such as the mouth, the epipharynx, 
the palps, the caudal styles. Of recent years, as 
the result of experiment on one hand and histo- 
logical analysis on the other, there has been a 
tendency to conclude that the antennz are the 
olfactory organs. The antenne are rich in 
sensory structures, and their removal is some- 
times followed by a negative reaction to an odour 
which is attractive to the intact insect. Dr. 
McIndoo thinks that the arguments are very in- 
conclusive. 
There are certainly many structures on the 
antenne which might be olfactory—pore-plates 
(Lubbock’s pits), pegs (Lubbock’s cones), Forel’s 
flasks, pit-pegs, and end-rods; and each of these 
has been claimed by some investigator as the 
true and only seat of smell. But in all these 
structures the nerve-ending is shut in by the chitin- 
ous cuticle, through which, therefore, the odour 
would have to pass. Another difficulty em- 
phasised by Dr. McIndoo is in regard to the dis- 
tribution of the structures above-mentioned: thus 
the pore-plates cannot be the exclusive olfactory 
structures, for they are absent in all Lepido- 
ptera; the pegs cannot be the exclusive olfactory 
structures, for they are absent in many male bees, 
and so on. The distribution of the various 
antennary structures in different types does not 
correspond with the varied rates of response to 
odours as shown by these types under experi- 
mental conditions. Moreover, spiders can smell, 
and they have no antenne. The author concludes 
that for ants, bees, and wasps, the antennz can 
no longer be regarded even as a possible seat of 
the sense of smell. It is possible, however, that 
what is true of one order of insects may not hold 
for another. 
What, then, is to be made of the experiment 
repeatedly performed of removing the antenne 
and observing that the usual response to odours 
did not occur? The author’s numerous experi- 
ments on Hymenoptera have shown him that if 
the antenne of these insects are mutilated even 
a little, the behaviour becomes abnormal, and 
the slow reaction to odours may be due to the 
actual injury, not to the removal of some of the 
olfactory structures. Amputation of the antennz 
1 “ The Olfactory Sense of Insects.” 
sonian Miscellaneous Collections. 
6 figs. 
By Dr. N. E. McIndoo. Smith- 
Vol. Ixiii (1914), number 9. Pp. 1—63, 
NO. 2380, VOL. 95| 

. the seat of the 
is often fatal, and the insect is so much dis- 
organised that its failure to respond to attractive 
odours does not prove that the olfactory struc- 
tures are on the antenne. Details are given in 
support of this useful criticism. 
Where, then, is the seat of smell? Dr. McIndoo 
takes us back to the work of Hicks (1857), who 
discovered vesicles or pores on the bases of the 
wings and on the legs, and suggested that they 
were olfactory. The structures have been 
studied by Janet and others, as well as by Dr. 
McIndoo. Each is like an inverted flask im- 
bedded in the chitin, but with a minute external 
pore. A fibre from a sensory cell near the inner 
end of the flask rises to the pore, and its cyto- 
plasm comes inte direct contact with the air and 
its odorous particles. These pores correspond to 
the lyriform organs or slits discovered by Bertkau 
on the legs of spiders, and subsequently studied 
by Dr. McIndoo. When the pores on insects’ wings 
are covered with glue or vaseline the reaction 
times are greatly increased, and the rates of 
response in particular insects correspond with 
the number of pores. A drone hive bee has 
2600 pores, and responds in 2°9 seconds; a 
worker has 2200 pores, and responds in 374 
seconds; and a queen has 1800 pores and re- 
sponds in 49 seconds. The author is to be con- 
gratulated on his introduction of some order 
into the chaos of discrepant opinions concerning 
sense of smell in insects. 

SUR TAH. CHURCH, KG VsOr, HARA. 
HE announcement in Nature of June 3 
of the death of Sir Arthur Herbert Church, 
in his eighty-first year, has been received with 
great regret among men of science. Sir Arthur 
Church was educated at King’s College, London, 
the Royal College of Chemistry, and Lincoln 
College, Oxford, where he took a First in the 
Natural Science School. He afterwards became 
Professor of Chemisty in the Royal Agricultural 
College, Cirencester. This appointment naturally 
led him to devote special attention to agricultural 
chemistry, on which he became an authority, and 
at the same time to direct his attention to the 
chemistry of plants. He contributed memoirs 
on vegetable albinism; colein or erythrophyll; and 
aluminium in vascular cryptogams, etc., and 
also investigated the remarkable animal pigment 
known as Turacin, which contains 7 per cent. 
of metallic copper. 
Sir Arthur Church also directed his attention 
to mineralogical chemistry, being the first to dis- 
cover Churchite, a native cerium phosphate, and 
several other new minerals; and he was at one 
time president of the Mineralogical Society. His 
researches in other departments of applied 
chemistry seem, however, to have been influ- 
enced by his strong interest in art in every form. 
Perhaps few chemists know that Sir Arthur Church 
once exhibited at the Royal Academy, besides 
