INSECTS WHICH PREY UPON AGRICULTURAL PLANTS. 89 



aphis and lay one egg. This hatches into a grub, which lives 

 on the substance of its " host," and eventually kills it. 



Aphis humuli (the Hop Fly). — This is the great pest of the 

 hop crop. It appears in the middle of May, when the bines are 

 about four or five feet high, on the under side of the topmost 

 leaves. The aphides are very susceptible of atmospheric 

 changes, and do not appear some seasons at all. Syringing 

 with an infusion of tobacco juice is the method usually employed 

 to kill them, while the " lady-birds " destroy them in large 

 quantities. 



Aphis hrassiccc (the Cabbage Aphis). — This is one variety of 

 aphis which infests cabbages and turnips, doing much harm by 

 inserting its suckers and drawing away the juices, and thus 

 causing a diseased growth. It is dull green covered with a 

 grey powder. The females are wingless. Syringing with 

 soap-suds or tobacco juice w^ould be the best method of deal- 

 ing with them on a limited scale, as in a garden. Turnips 

 afiected with mildew are, in the early stages, more apt to 

 succumb to them as they (the turnips) are not healthy enough 

 to resist their attacks, so that keeping up a good strong growth 

 is the best way of treating this pest. 



Aphis dianthi (the Turnip Aphis). — This species is especially 

 liurtful to turnips, swedes, and potatoes wdien growing, some- 

 times occurring in vast swarms so as to completely smother the 

 plant. There are both winged and wingless females, the former 

 of a black colour, and the latter greenish. Dressings of any 

 kind of wash cannot be economically applied to a large field of 

 turnips, but if these are supplied with sufticient food at their 

 roots they will not suiter so much. 



Tlirips cercalium (the Corn Tlnips).-;-Tliis is a little black 

 slender insect which does much damage to the corn crops. The 

 imago is smooth and shining, and about one-sixteenth of an inch in 

 length, the female only being winged, and the wings being ciliated 

 with long hairs. They cause intolerable irritation when they alight 

 on tlie hands and face by running and leaping with their bladder- 

 shaped feet. Injury is done to the seed by their sucking the 

 juice, and they attack various corn crops. The only preventive 

 is to sow as early a.s possible, in order to have the plants vigorous 

 before they appear. 



Eaplcrijj) solani (the I'otato Frog-lly.) — It is of a lively green 

 colour, but fades to yellow after death. The abdomen tapers to 

 a point; the head is broad with lateral ])roniinent brown eyes; 

 the wings arc twice as long as the abdomen, glossy, and the 

 U]»per ones or "elytra" are rusty at the extremity. The length 

 of the full-sized insect is about one-eighth of an inch. The mouth 

 is moditied into a " rostrum" or snout which folds under the hciid 

 and thorax. 



