Athalia nearly resembles Hylotoma and Selandria, but is 

 distinguished from both by its antennae, which are more cla- 

 vate than the latter and have more joints than the former. 

 Di-. Leach described them as 10-jointed, but in the species 

 figured the males have only 9 joints (fig. 1.), and in the females 

 an nth joint is indicated. Six species are recorded in the 

 Guide as British, and the one before us is well deserving our 

 attention from the injurious habits of its larva. 



The T. spinarum is stated by Fabricius to be destructive to 

 turneps, and the T. centifolicc of Panzer is undoubtedly the 

 same species. 



In walking through the turnep-fields last year the most 

 casual observer must have noticed the mere skeletons which 

 the leaves often exhibited, the fibres only remaining, the mem- 

 brane being consumed by larvae called Blacks by the farmers. 

 From the middle of August to the 20th of October, at which 

 lime they were full-grown, I observed them feeding on the 

 leaves of the turneps; they often varied considerably in stature, 

 and the bulb was evidently reduced in size through their 

 agency. The larvae or caterpillars when full-grown are some- 

 times green, but generally of a lead or slate colour, being black 

 before changing their skins, and always appearing darker when 

 rolled up : they form an oval horny cocoon either amongst the 

 leaves on the ground or under the clods of earth, where they 

 become pupae. The fly appears principally in August and 

 September, but I have found them as early as the 29th of 

 March, and as late as the middle of October. I first observed 

 these flies in abundance in a potato-field at Battersea, and 

 afterwards in a field near Heron Court ; but last year they 

 were distributed over the whole country, after an absence in 

 many places, I was informed, of upwards of 30 years ; they 

 have appeared again this year, and Mr. R. Taylor and my- 

 self, in a botanical excursion last August, saw the flies coming 

 out of the ground in myriads in a ploughed field near Bristol, 

 where potatos had apparently been grown. 



The Jlies do not appear to be attached to any particular 

 plant ; whether the larva; will attack any other than the En- 

 glish turnep I cannot determine, but it is a remarkable fact 

 that they will not touch the Swedes. I believe it is not diffi- 

 cult to destroy them, for if they are brushed off the leaves it 

 seems they are unable to crawl upon the ground and recover 

 their station ; they consequently perish unless they are fiill- 

 grown at the time : but as there is a constant succession from 

 August till near November, the operation of drawing a hurdle 

 or something over the turneps ought to be repeated at inter- 

 vals during that period. Wet, also, is said to destroy the 

 blacks, and ducks turned into the fields clear them off' rapidly 

 and grow fat upon them. 



The full-grown larva is represented feeding upon the tur- 

 nep, Brassica llapa. 



