Turnip Saif-Flj/. 195 



the attacks of the turnip flea upon the cotyledon leaves are, at 

 a later period, liable to be destroyed by this nigger caterpillar. 



The time of the appearance of the caterpillars is stated by 

 Mr. Curtis {Btitish Entomoloiii/, October, 1836. pi. 617., folio 

 a) to extend from the middle of August to the 20th of Oc- 

 tober. From the observations of other writers, it would, how- 

 ever, appear that the former is the chief period for the appearance 

 of the niggers ; those found in the middle of September being 

 termed by one writer (W, C, in Sali/rdaj/ Alag., vol. vi. p. 181.) 

 as " several stragglers, or perhaps larvae, of a second brood ; " 

 and Mr. Yarrell, in the above extract, speaks of " variot/s 

 broods," the members of which destroy the produce of the sub- 

 sequent sowings. This is, however, a question upon which 

 more precise information is required. 



When the caterpillar is full grown, it descends into the earth, 

 where it buries itself at a little distance from the surface, forming 

 an oval cell in the earth by the motion of the body ; the external 

 particles of earth and sand being agglutinated together {^g. 73. c), 

 and the interior very smooth, and lined with a silvery-coloured 

 shining matter, evidently caused by some secretion, either from the 

 pores of the body or the mouth, which has dried and hardened. 

 Mr. Curtis states that these insects form an oval horny cocoon, 

 either amongst the leaves on the ground, or under the clods of 

 earth, where they become pupae ; but those which I have seen, 

 and which were placed in my hands by Mr. Yarrell, corresponded 

 with my description. It does not appear to have been ascer- 

 tained how long the insect remains in the pupa state. Mr. 

 Yarrell, indeed, tells us that, on opening one of the cocoons on 

 Nov. 16., the larva was found to have undergone little or no 

 change at that time : the cateipillar was alive and soft. In some of 

 those cocoons which I opened in the month of May following, the 

 insect was in the pupa state (Jig. 73. d) : and, indeed, it is the habit 

 of some of the saw-flies which I have reared, to remain unchanged 

 in the larva state all the winter, and not to assume the pupa 

 state until a very short time previous to tl>eir appearance in the 

 perfect winged state. If, however (and here, again, we are de- 

 ficient in our facts), there be several broods in the course of the 

 autumn, it is most probable that the period between the full- 

 grown larva and winged states does not extend beyond a few 

 days. It is in the month of July that the first winged insects 

 make their appearance from the ground. They are technically 

 known under the name of Athali« centifcMipe. 



Order, Hymenoptera Linnceus. (Membranous four-winged flies, witli saws 

 or stings at the extremity of tlie abdomen.) 



Section, Serrifera (Saw-bearers) Latrcille. 



Family, T'enthredlnidge ( Saw-flies) L(?«c/^ (So named from, and correspond- 

 ing in extent with, the Linngean genus T'enthrcdo.) 



o 2 



