176 



INJURIOUS INSECTS AND FUNGI. 



[Sept. 1895. 



The flea-beetle not only attacks turnips and swedes, but is often 

 very destructive to rape, mustard, cabbage, kohl-rabi, and other 

 cultivated cruciferous plants. 



There are at least two other species of flea-beetles which are 

 injurious in a less degree to turnips and other plants of the 

 same order. These much resemble Phyllotreta nemorum, and 

 can only be differentiated by close observation. Of these 

 Fhyllotreta tmdulata is the most common. It resembles 

 Phyllotreta nemorum^ but is rather smaller, and the yellow 

 stripes on the wing-cases are somewhat differently arranged. 



Life History. 



The Turnip Flea is very small, being only about one and a 

 quarter lines long, as shown in Fig. 3 of the above illustration, 

 which Messrs. Blackie and Son have courteously allowed to be 

 reproduced. It is black, with a broad yellow stripe down each 

 elytra or wing-case. The antennae have three ochreous-coloured 

 joints nearest the head, and eight dark -coloured joints. The 

 legs are ochreous, or yellow, and the thighs, which are very 

 stout, are well adapted for the long jumps which this insect 

 can make. Curtis states that it can jump 18 inches, or 216 times 

 its own length. It passes the winter in beetle form under clods 

 and stones, in tufts of grass, among weeds, and under rubbish 

 of various kinds, by the sides of fields, hedgerows, and ditches 

 It is thus sheltered during the winter, and it is sustained 

 throughout the early spring-time until the turnips have sprouted, 

 upon wild cruciferous plants, such as charlock, hedge-mustard, 

 and wild radish. It has large and powerful wings, expanding 

 more than the fourth of an inch (Figs. 1 and 2), and takes long 

 flights in search of congenial food, which, some say, it scents 

 from a distance. It attacks the young turnips, biting and 

 devouring their soft tissues, and lays eggs on the under sides of 

 their second or " rough " leaves. From these eggs, tiny yellow 

 larv?e come at the end of from seven to eight days (Figs. 8 and 

 9), and make mines (Fig. 7) in the leaves, feeding upon the soft 

 tissues, and much weakening the plants. When full grown, 

 the larvae are rather more than 2 J lines long, with six feet 

 and a caudal proleg, or " sucker foot." They have dark marks 

 upon the anterior and posterior parts of their bodies. In the 

 course of from five to seven days, they fall to the ground and 

 change to pupae (Figs. 10 and 11), from which, in about 12 days, 

 the perfect beetles come and proceed to attack the turnip plants. 

 It is said that as many as six generations may be produced 

 in a season, if the conditions are suitable. 



Methods of Prevention. 



Sowing upon a " stale furrow " is calculated to prevent the 

 attacks of this beetle. A stale furrov/ usually implies a " good 



