THE AMERICAN ENTOMOLOGIST. 



6i 



the mine to pupate. The larva of L. robini- 

 ella like that of L. ornatella is found in both 

 surfaces of the leaflets, and is what is tech- 

 nically termed a tentiform mine, — that is, 

 it is a large white blister-like spot. Its 

 larva up to its third stage is flat and white, 

 and after that becomes cylindrical. The 

 larva of the beetle is much larger than 

 either of those of Lithocolletis. The fourth 

 mine is that of Gracilaria {Parectopa) 

 robiniella. It is pale yellowish and extends 

 along the midrib on the upper side of the 

 leaflet, sending off finger-like processes on 

 each side. The larva is somewhat de- 

 pressed, by which fact it may be dis- 

 tinguished from the larva of L. robmiella. 

 These larvae of Lithocolletis and Gracilaria 

 have each only six legs ; but in their mines, 

 and especially in the mines of L. robinietla, 

 may frequently be found a larger, striped 

 larva with eight legs ; this is the larva of 

 Gelechia pseudacaciella before mentioned. 



Fully nine-tenths of the depredations of 

 insects on locust trees in this locality are 

 the work of Hispa suturalis, Lithocolletis 

 robiniella, L. ornatella, G. robiniella and 

 Cecidomyia robinice, and probably one-half 

 of it is the work of LL. suturalis. 



When we look at a grove in August the 

 wonder is not that it should be destroyed 

 by these depredators, but that it does not 

 succumb much sooner than it does. It 

 will continue to live, in spite of its injuries, 

 for several years, the trees gradually dying 

 out one by one. The young trees seem to 

 suffer most, as the insects seem to prefer 

 their foliage ; and large old trees seldom 

 exhibit the burnt appearance of the young 

 groves. Young shoots growing up around 

 an old trunk will sometimes have nearly all 

 their leaves blistered, while but few com- 

 paratively of those on the old tree will be 

 injured. 



No means of checking the ravages of 

 these species are at present known, other 

 than those afforded by nature, and these 

 seem wholly insufficient. I have bred two 

 species of Chalcid parasites from L. robini- 

 ella, and two from L. ornatella, and one 

 from Gracilaria robiniella, and there are 

 also parasites which prey upon LLispa sutur- 



alis; but although these parasites are abund- 

 ant they are not numerous enough to check 

 perceptibly the devastations of the leaf- 

 mining larvse. Economic Entomology may 

 and it is to be hoped will accomplish much 

 in the future ; unfortunately, man is at 

 present very much at the mercy of his con- 

 temptible little foes. 



^ -^ 



THE INSECT ENEMIES AND DISEASES OP OUR 

 SMALL FRUITS. 



[Read before the New Jersey State Horticultural Society, 

 Jan. 16, 1880, by A. S. Fuller.] 



Insects and diseases are frequently so 

 closely united, or so dependent upon each 

 other, that the naturalist often finds it dif- 

 ficult to determine to which the fruit-' 

 grower should attribute his losses. Some 

 species of insects attack only diseased or 

 dead plants ; others only the living and 

 healthy. If a plant shows signs of failing 

 we are inclined to speak of it as being dis- 

 eased, whether the failure is caused by a 

 lack of some element in the soil, attacks of 

 parasitic fungi, or noxious insects. The 

 loss is the same in the end, whether from 

 one or all of these enemies combined. 



There are two practical methods of com- 

 bating insect enemies and diseases of 

 plants ; one is to so carefully cultivate 

 and stimulate the growth of the plants that 

 they may possess the power of resisting at- 

 tack ; the other is to make war directly 

 upon them by artificial means. Of course, 

 the first method is most applicable or prac- 

 ticable against the more minute species, such 

 as the plant-lice, rust, smut, and mildew. 

 I do not recommend forcing plants to 

 extremes, in order to enable them to resist 

 their enemies, as this might work an irre- 

 parable injury ; but the condition to be 

 aimed at should be a healthy, vigorous 

 growth ; for anything beyond this, is more 

 the sign of weakness than strength. 



The half-starved, over-worked, and un- 

 cared for horse is sure, sooner or later to 

 become the prey of various kinds of inter- 

 nal and external parasites, which are thrown 

 off, or their attacks successfully resisted by 

 the healthy, vigorous and well fed animal ; 

 and the same principle holds good all 



