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INSECTS. 
Heliothripg hcemorrhoidalis 
(greatly enlarged). 
furnished instead with small vesicular lobes, by means of which they adhere to 
the surface on which they rest. To these characters of the order we may add that 
the body is narrow and cylindrical; the 
thorax is formed of three, and the ab¬ 
domen of ten segments; there are only 
three or four pairs of spiracular openings 
—two on the abdomen, and one or two 
on the thorax; three ocelli are generally 
present on the head in addition to the 
fairly large faceted eyes; and the 
antennae are composed of from seven to 
nine joints. The larvae have a general resemblance to the adult 
insects, and in their last stage they remain inactive and take no 
nourishment. Less than a hundred species of Thysanoptera, 
belonging mostly to the European fauna, have been described. 
These little insects are frequently to be seen on flowers, and on 
other parts of plants. They feed upon the juices, and when present in large 
numbers are capable of doing an appreciable amount of injury. Some destroy 
the pollen grains, and so prevent the fertilisation of the flowers. The corn-thrips 
{Thrips cerealium ) sucks the young grains on the ears of corn, and stops their 
further growth. Heliothrips hcemorrhoidalis, another species which we figure, is 
common in hothouses, where it may be found on the young buds of several 
different kinds of plants. 
Order THYSANURA. 
FEMALE CORN-THRIPS 
(much magnified). 
The Thysanura are active little insects, which live generally in obscure places 
and are mostly of too small a size to attract much attention. They never exhibit 
any trace of wings, undergo no metamorphosis, and have a distinctly segmented 
body, which is usually covered with hairs or scales and furnished behind either 
with a forked tail, used as a springing 
apparatus, or with two or three long, jointed 
appendages, which sometimes serve a similar 
purpose. Characterised on the whole by a 
somewhat primitive type of structure, and, 
in general appearance resembling the larvae 
rather than the adult forms of other insects, 
the Thysanura are in some cases distinguished 
by special features of great interest. The 
spring-tails (Collembola) are all furnished on 
the under side of the first abdominal segment 
with a curious tube or sucker, from the 
mouth of which a glandular process, secreting 
a viscid matter, can be protruded; they are 
remarkable also from the fact that in most of them no trace of a tracheal system 
has yet been discovered. In the Collembola the eyes, when present, are in the form 
of simple or grouped ocelli; the antennae number not more than six joints, and the 
Podura villosa (nat. size and greatly enlarged). 
