124 Objects for the Microscope. 



occasion for food, and therefore the milk was not detained 

 in the crop, the intestines having the power of digesting it. 

 Another time Hunter allowed some flies to feed plentifully, 

 and then found the crop quite full, as well as the intestines. 

 Insects have no absorbents ; the chyle, which is a clear, 

 greenish fluid, with round oval corpuscles, is supposed to 

 transude through the coats of the intestine into the abdo- 

 men, where it meets with the blood in the ill-defined veins 

 that permeate the body. (See ' Owen's Lectures on Comp. 

 Anat.') * 



The tracheal vessels or breathing organs have been noticed 

 in the chapter on spiracles and tracheae. 



The nervous system is similar to that of other insects, 

 consisting of two spinal cords or threads, exhibiting a series 

 of knots or ganglions. The Fly has one in the head, a very 

 large one in the thorax, and one, or sometimes two, in 

 the abdomen ; these give out nerve-branches to the wings, 

 halteres, and legs. 



In looking at a slide of Culex observe the length of the 

 coxa, and the small joint called trochanter, between the coxa 

 and femur. 



If possible, obtain the male of Culex annulata with its 

 magnificent antennae and feathered palpi, and the female 

 of Culex pipiens for the display of the suctorial mouth. 



PTYCHOPTERA. 



This is one of the family of Tipulae, Crane-flies, or 

 Daddy-long-legs, which abound in the neighbourhood of 

 water, and are recognised by their black and yellow bodies 

 and spotted wings. The larva is an aquatic worm, and 

 the pupa has a curious, long, thread-like appendage, 

 through which it breathes. We find it in shallow water 

 at the brink of muddy ponds. 



The wing is a good study after that of the Gnat, as 

 an example of wings without scales, and of the peculiar 



* The stomach of the Fly, mounted in balsam, is an interesting object 

 and kept in most collections for sale. 



