Life History. 



The life histories of a majority, even of the economic species 

 of Cicadellidse, have not been fully v^^orked out. Some have, 

 however, been worked out in detail, so that it is fairly easy to 

 g-ive a general life history for the group. 



These insects belong to an order in which the metamorphosis 

 is incomplete, that is, there is no distinct pupal or quiescent 

 stage in the life cycle. It would, however, be better to speak of 

 them as having a gradual metamorphosis rather than an incom- 

 plete one, reserving the latter term, as pointed out by Professor 

 Comstock, for such water forms as dragon flies, which do not 

 resemble the adult at all in their imperfect stages and yet can- 

 not be said to have a complete metamorphosis. Thus there are 

 three stages in their life cycle, namely, egg, nymph and adult. 



The female leaf hopper is provided with a strong enough 

 ovipositor to enable her to push the eggs in under the covering 

 of some plant tissue. There is of course a great deal of dif- 

 ference in the different groups, and even among the species of 

 the same genus, in the kind of material chosen for egg deposi- 

 tion, it being the rule that the eggs are always deposited in the 

 kind of plant which is to furnish food for the nymphs on 

 emerging. 



In general it may be said that grass-feeding species deposit 

 their eggs either between the sheath of the blade and the stem, 

 or else in the margin of the leaf, where a layer of epidermis 

 covers the egg. In either case the eggs are protected by a part 

 of the host plant. Other forms deposit their eggs in the veins 

 of leaves or sometimes under the epidermis in the tissue be- 

 tween the veins. Such is the case with the grape-leaf hopper, 

 the potato-leaf hopper and a host of others. Still others de- 

 posit eggs in the stems of their host plants. This is true of 

 such forms as the rose-leaf hopper, the apple-leaf hopper {Em- 

 poasca imicolor) and others. Some, such as the clover-leaf 

 hopper, deposit their eggs either in the leaves or the stems of 

 their host plant. In a few cases also the same species may 

 oviposit alternately in two different hosts. This has been 

 shown to be the case with the rose-leaf hopper, the overwinter- 



(22) 



