affecting the Corn-Crops. 
515 
Females in swarms, males very seldom seen. 
A second species in corn-fields, called Platyyastcr Tritici ; and 
there is a vast number of other species. 
Platijgaster inser ens lays its eggs in those of the P. Tijmlce, 
and limits its increase. 
Macroglenes penetrans is also occupied in the same way, but lays 
its eggs in the maggots of the Platygaster Tipuke. 
Flies called Empidcs carry oft" and devour the wheat-midge. 
A little insect called Thrips accused of injuring the corn-crops. 
Some species destroy peaches and melons, cucumbers, olives, and 
hothouse plants. 
Thrips cerealium destroyed one-third of the wheat crop in the 
richest plains of Piedmont in 1805, and it is believed affected the 
same crops in England. 
It causes the rge to be unprolific in Scotland, and also ia 
Sweden. 
The larvcp and pupa; are similar to the perfect Thrips, but the 
first is of an orange colour, the others are black, and the female 
only has w ings in her last stage. 
Abundant in summer in the ears and between the leaves, at the 
base, in reheat and barley plants. 
It is the most numerous of all the insects infesting the wheat, 
and common every year. 
Pungled, or shrivelled grains, caused by the Thrips extracting 
the milky secretions, and abortion frequently occurs from their 
piercing the tender straw at the joints. 
One fouj'th part thus destroyed in some ears. 
Orange-coloured larv(B very active, pupcB indolent. 
The orange-coloured powder often accompanying them is not 
their excrement, but a. fungus called Must. 
They do most mischief to late-sown w heats, the earhj-soicn being 
too hard to suffer from their attacks. 
Apparently more injurious on heavy than on ligJit soils. 
In some years the bearded wheat escaj?ed, in others it has suffered 
most. 
Earwigs with them. Do they live upon the Thrips^ 
Minute as the Thrips is, it is infested by a parasite, and is often 
covered with mites which feed on it. 
Aphides, or plant-lice, called also dolphins, infest the wheat in 
July and August ; when they are in every stage of growth. 
Aphis granaria also inhabits barley and oats. 
Every Aphis sometimes punctured by a parasite, and the ears 
exhibiting numbers of broicn and black globules scattered over them. 
Aphidius Avence lays her eggs in the body of the apterous 
which then becomes brown. 
