202 



INSECTS. 



Hdiotlirips hcemorrhoidalis 

 (greatly enlarged). 





FEMALE CORN-THRIPS 



(much magnified). 



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. Helioihrips 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. 



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 w r hich 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). 



