Observations on Insects affecting the Turnip Crops. 67 



in every garden, field, and hedge, and I have bred them even in 

 October. The maggots are yellowish-white, with broken scarlet 

 lines down the back, and black spots and marks between them, 

 which are caused by the food in the intestines shining through ; 

 the head is furnished beneath with two minute hooks or teeth, 

 and there is a tubercle at the rump composed of two lobes^ with 

 which the animal adheres to any object ; and there are minute 

 bristles on the sides. Out of one of the pupre came three or 

 four little parasitic maggots, which lived through the winter ; and 

 the first week of April they produced some small flies, very 

 similar to No. 8, ^vhich I take to be the Ceraphron Syrphii of 

 Bouche,* who bred them likewise from the pupae of S. Rihesii. 

 One of the Ichneumonidae, called by Gravenhorst Bassns albo- 

 signatus,^ also lays its eggs in the larvae of ^S*. halteata. 



22. S. scripta, Linn, is much smaller than the foregoing in- 

 sects, and the males have a much narrower body : the face is 

 yellow ; the horns orange ; thorax dull green, the sides and 

 scutel yellow; body long and narrow in the males, with two 

 bright ochraceous spots towards the base, two bands of the same 

 colour farther down ; the penultimate segment has a V-shaped 

 ochraceous mark on the centre, with a dot on each side, and the 

 apex is also ochraceous, with a few black dots; the legs are 

 entirely ochraceous; length 4f lines, expanse 7 lines. 



This and many allied species are abundant everywhere, espC' 

 cially in meadows and ditches, from Midsummer to October. I 

 may mention also that the Baron De GeirJ] describes and figures a 

 blood-red Acarus or mite which seizes the Aphides by the back, 

 belly, or neck, as a ferret would a rat, and sucks out all the juices ; 

 and I find that earwigs assist in diminishing the plant-lice, by 

 feeding upon them in the curled leaves, where those troublesome 

 insects shelter themselves after their nocturnal excursions. 



Severe frosts are exceedingly beneficial in the destruction of 

 noxious insects, and although the Aphides can resist cold to a 

 considerable amount, having survived the weather when the 

 thermometer was as low as 29° Fahr., not only are immense 

 quantities destroyed by intense cold, but a check is given in 

 another way to their increase, for in mild winters little doubt can 

 be entertained that they not only survive, but are actually propa- 

 gating ; and Mr. W. Curtis very sensibly remarks, that as their 

 enemies, on the contrary, exist, but do not multiply, during such 

 periods, the Aphides get the start of them, and thus obtain an 



* Bouche's Naturg. der Insecten, p. 175, pi. 7. fig. 33 and 36 to 39 and 

 fig. 41. 



t Curtis's Guide Gen. 520, 20. 



% Memoires, v. 7, p. 122, pi. 7, fig. 13, U. 



f2 



