258 



(ESTBUS OVIS, OR GADFLY OF THE SHEEP. 



By A. MoKTON, Curator Eoyal Society's Museum. 



[Read October 13, 1884.] 



A few notes on the introduction of what I am led to 

 believe to be a new grub or fly to Tasmania, may bo of some 

 use to the Felbws of the Eoyal Society. The above insect, I 

 find, is not of any recent date, but is spoken of by a learned 

 physician, Alexander Trallien, in the year 560. They are 

 well-known in Europe, and have been met with at times in 

 the Australian colonies. 



About 10 days ago Mr. Maddox, who is connected with a 

 butchering establishment in this city, brought me in a grub 

 that is on the table, saying that in cutting open a sheep's 

 head, near the brain, he found this grub. The sheep it was 

 taken from was one recently introduced from the neighbour- 

 ing colonies ; in none of the Tasmanian sheep, he states, has 

 he found anything like this. Several other gentlemen con- 

 nected with sheep in this colony have also expressed similar 

 opinions. On examination, and referring to some works on 

 the disease of sheep, I find it to be the (Estrus ovis, or Gadfly 

 of the sheep, belonging to the Diptera order, so named from 

 its larvae inhabiting the nostrils or frontal sinuses of sheep 

 in particular, although it has occasionally been found in 

 goats and deer. In Europe, it assumes its perfect winged 

 form in some uncertain period from May to July ; it then 

 becomes an intolerable nuisance to the sheep, especially in 

 woody countries and in the neighbourhood of copses ; so 

 much so that if only one fly appears, the whole flock is in the 

 greatest agitation. The larvse or grub is composed of 10 or 

 11 rings ; when young it is perfectly white, with the excep- 

 tion of two small brown patches by the side of each other at 

 its tail. At some time between the middle of July these 

 larvse have attained their full growth and seek to 

 escape from their prison. While this is taking Y>lsice great 

 annoyance is caused to the sheep, continually stamping their 

 feet and sneezing violently. It is stated that the exit of the 

 grub is seldom seen, owing probably to the impatience of the 

 sheep. Very rarely are more than three of these lots found 

 in a sheep's head ; some instances have, however, been c[uoted 

 where a head has contained nearly a dozen. M. Valisnieri, a 

 French naturalist, states that a worm which he took on July 

 the 5th underwent its final change at the expiration of 40 

 days, but 63 days passed before one which he found in April 

 became a perfect fly. The fly is considerably smaller than 

 the size of the larva would indicate, the length of the wings 

 being nearly ecjual to that of the body, which they almost 

 entirely cover ; they are described as being prettily 



