3 i68 



N 



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 nour- 

 ishment. L,ess 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. 

 FEMALE CORN THRIPS S me destroy the pollen grains, and so prevent the fertiliza- 

 (Much enlarged.) tion 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. 



Heliothrips hcemorrhoid- 

 alis (greatly enlarged). 



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 appa- 

 ratus, or with two or three long, jointed ap- 

 pendages, which sometimes serve a similar 

 purpose. Characterized 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 

 springtails (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 

 abdomen has at most but six segments and very often only three. The forked tail, 



Podura villosa. 

 (Natural size and greatly enlarged.) 



