416 



DIl'TERA. 



:{ "'' 



barley, from six to ten larvae being found in each, and by de- 

 stroying the flowers render the ear sterile. Osciitis frit Linn. 

 in Europe inhabits the husks of the barle} r , and destroys one- 

 tenth of the grain. Linnaeus calculated the annual loss from 

 the attacks of this single species at half a million dollar.-,. 

 Ploughing and harrowing are of no use in guarding against 

 these insects, as they do not transform in the earth ; the best 

 remedy lies in the rotation of crops. Many of these small 

 flies, like the micro-lepidoptera, are leaf-miners, and are not 



readily distinguished from 

 them when in the larva state. 

 Of the genus Pliora, a 

 European species (P. incras- 

 sata Fig. 339 ; o, larva ; fr, 

 puparium) frequents bee 

 hives, and is thought by some 

 to produce the disease 

 which is known among apiarians as "foulbrood." 



In the pupiparous Diptera, namely, those flies which are born 

 as pupae from the body of the parent, the larva state having 

 been passed within the oviduct, the thorax is more closely 

 agglutinated than before ; the head is small and sunken in 

 the thorax, and in the wingless species this consolidation of 

 the head and thorax is so marked as to cause them to bear a, 

 remarkable resemblance to the spiders. Spider-like in their 

 looks, they are spider-like in their habits, as the names Spider- 

 flies, Bat-ticks and Bird-ticks, imply a likeness to the lower 

 spiders or ticks. The antennas are very deeply inserted and 

 partially obsolete ; the labrum is ensheathed by the maxilla% 

 and the thoracic nervous ganglia are, as in the Arachnida, 

 concentrated into a single mass. 



HIPPOBOSCID^E Westwood. The Forest-flies and Sheep 

 Ticks are characterized by the horny and flattened body, the 

 horizontal flattened head received into the front edge of the 

 thorax, the large eyes, the rudimentary papilla-like antenna? 

 placed very near together, and the proboscis is formed by the 

 labrum and maxillae, whose palpi are wanting ; the labium is 

 very short ; wings with the veins present only on the costal 



