WING OP SCATOPHAGA. 91 



SPIUACLES OF LARVA OF BOT-FLY. 

 (CEstrus.) 



See egg of GEstrus for an account of the Bot. 



WINGS OF INSECTS. 



There is much to learn in the wings of Coleoptera, 

 Hemiptera, Hymenoptera, and Diptera. The scales or fea- 

 thers which clothe the wings of Lepidoptera are noticed 

 under Scales of Moth. The Diptera are classed by the vein- 

 ing of the wings, and therefore it is absolutely necessary to 

 have a few specimens mounted as lessons for the names of 

 the nerves or veins of the wing. 



The wing itself may be described as a transparent mem- 

 branous organ, consisting of two laminae, or plates, which 

 are united by canals called veins or nerves. These veins are 

 hollow channels through which the circulating fluid flows, 

 and a trachea! vessel runs in communication with the tracheae 

 in the thorax. 



In the Ladybird's (Coccinella) wing, the blood is not con- 

 fined to these canals or veins, but circulates freely through a 

 large part of the wing. The circulation may be seen in the 

 wing of any newly-hatched fly, but especially in that of the 

 beautiful lace-winged fly, Hemerobius, where it was first 

 noticed by Dr. Bowerbank. 



WING OF SCATOPHAGA. 



Although this is fully described for the slide of Scato- 

 phaga, mounted whole, it is mentioned here as the best 

 lesson on the veins, and very easily put up separately. If 

 merely mounted dry, the veins are sufficiently seen, but when 

 soaked for a few days in turpentine and mounted in balsam, 

 they become transparent from the expulsion of the air ; and 

 then not only the canals, but the tracheae, may be visible, 

 especially in the costal vein. 



Observe that strong vein bordered with hairs on the fore- 

 margin of the wing that is the Costal vein; and in the 



