1200 Insects. 



that, in this part of the country, a very large proportion, probably more than nine 

 tenths, of every generation of this fly is thus destroyed. One of these parasites was 

 made known by Mr. Say, in the first volume of the ' Journal of the Academy of Natu- 

 ral Sciences of Philadelphia ; ' and the interesting discovery of three more kinds is due 

 to the exertions of Mr. Herrick. They are all minute Hymenopterous insects. The 

 chief parasite of the pupa is the Eurytoma destructor, (Ceraphron destructor of Say). 

 This has often been mistaken for the Hessian fly, from being seen in wheat-fields, in 

 vast numbers, and from its being found to come out of the dried larva-skin of that fly. 

 In the month of June, when the maggot of the Hessian fly has taken the form of a flax- 

 seed, the Eurytoma pierces it, through the sheath of the leaf, and lays an egg in the 

 minute hole thus made. From this egg is hatched a little maggot, which devours the 

 pupa of the Hessian fly, and then changes to a chrysalis within the shell of the latter, 

 through which it finally eats its way, after being transformed to a fly. This last change 

 takes place both in the autumn and in the following spring. Some of the females of 

 this or of a closely allied species of Eurytoma, come forth from the shells of the 

 Hessian fly without wings, in which form they somewhat resemble minute ants. Two 

 more parasites, which Mr. Herrick has not yet described, also destroy the Hessian fly, 

 while the latter is in the pupa or flax-seed state. Mr. Herrick says, that the egg- 

 parasite of the Hessian fly is a species of Platygaster ; that it is very abundant in the 

 autumn, when it lays its own eggs, four or five together, in a single egg of the Hessian 

 fly. This, it appears, does not prevent the latter from hatching, but the maggot of the 

 Hessian fly is unable to go through its transformations, and dies after taking the flax- 

 seed form. Meanwhile its intestine foes are hatched, come to their growth, spin them- 

 selves little brownish cocoons within the skin of their victim, and in due time they are 

 changed to winged insects and eat their way out. "The following account" says Dr. 

 Harris " of my observations on the barley-straw, was published in the ' New England 

 Farmer,' in July, 1830. In winter, each maggot was imbedded in the thickened and 

 solid substance of the stem, in a little longitudinal hollow, of the shape of its own bo- 

 dy ; and its presence was known by an oblong swelling upon the surface. In some 

 pieces of straw the swellings were so numerous as greatly to disfigure the stem, the 

 circulation in which must have been very much checked, if not destroyed. Early in 

 the following spring these maggots entered the chrysalis state, and on the 15th of June 

 the perfected insects began to make their escape through minute perforations in the 

 straw, which they gnawed for this purpose. Seven of these little holes were counted 

 in a piece of straw only half an inch in length. The insects continued to release them- 

 selves from their confinement until the 5th of July, after which no more were seen. 

 They had destroyed all the flies that were the cause of the disease. The scientific 

 name given to them was Eurytoma Hordei." — Francis Walker; Grove Cottage, 

 Southyate, October, 1845. 



Dytiscus rnaryinalis. One of these kept in confinement left the water by night, 

 and flew about the room, returning to the vessel again by day. It fed on the tadpole 

 of the common frog. I never observed them devour their own species. — F. W. L. 

 Ross ; Broadway House, Topsham, Devon. 



K. NEWMAN, PRINTER, 9, DEVONSHIRE STREET, BISHOPSGATE, LONDON. 



