10 



All the other consignments of these insects which were received proved to be the cater- 

 pillars of the clover cut-worm (Mamestra trifolii). They appeared in large numbers 

 during the month of August and did considerable damage, particularly in fields of peas, 

 turnips and mangold wurtzel. This insect seldom appears in Canada as a serious pest, 

 nor from the condition of the consignments received by me do T anticipate that we 

 shall suffer from their attacks again next year. Of five lots of caterpillars sent 

 from different localities, nearly every specimen was found to be parasitised. One 

 lot of over a dozen caterpillars only gave, instead of moths, specimens of Ophion 

 purgatum, an active and beneficial Ichneumon fly, from the other larva; were reared 

 Tachina flies. A fact which has frequently been observed with regard to these cater- 

 pillars, and one which gives great comfort, is that whenever they -increase largely in 

 numbers they are invariably checked by the appearance of friendly parasitic insects. It 

 must be remembered that all insects are not injurious, but on the other hand that many 

 are very beneficial, preying upon and destroying injurious kinds. These belong to dif- 

 ferent natural orders. Amongst the Hymenoptera we find the Ichneumon flies. The 

 female is, as a rule, provided with a long slender ovipositor, by means of which she inserts 

 her eggs beneath the skin of her victim, or, as in the case of our largest species Thalessa 

 lunator, which has an ovipositor between four and five inches in length, pushes it into the 

 burrow of the woodboring host. The eggs of some are laid upon the outside of the skin 

 and not inserted beneath it. These parasites are some of them as Thalessa external feeders 

 lying alongside of their hosts, they pierce through their skins and suck out the juices, some, 

 and probably most, as the grub of the Ophion above-mentioned, after hatching, lie inside 

 the cavity of the body of the caterpillar, growing with it and feeding upon its blood, but 

 avoiding all vital portions. When full-grown they either eat their way out and pupate 

 in the ground or complete their changes inside the dead caterpillar. Of the Diptera 

 or two-winged flies, there are several spesies of Tachina flies, which closely resemble our 

 common house flies. These lay their eggs on the surface of the skin of the caterpillar, 

 to which they adhere firmly. When the young maggot hatches, it eats its way through 

 the skin into the body of its host and thrives at its expense. In addition to the above 

 there is a class of parasitic fungi which attacks caterpillars when thsy appear in large 

 numbers. One species Entomophthora virescens, Thaxter, has done good service in this 

 district by keeping down the larvse of Agrotis fennica. The work of this beneficial 

 fungus was detected again this year. 



The other attack which I have mentioned as having been of exceptional severity 

 during the past season was that of various kinds of locusts. These are generally incor- 

 rectly spoken of as grasshoppers. Early in June the fields in the neighbourhood of 

 Ottawa were found to be swarming with myriads of tiny locusts. Later in the season 

 these developed and committed serious depredations upon almost every green plant of a 

 few feet in height. Their numbers were so great that ordinary remedies were useless. 

 In an effort to protect some special plants a mixture of bran, sugar and arsenic, as sug- 

 gested by Prof. Riley, was used and certainly killed large numbers, but the dead bodies 

 and every green thing near them were soon demolished by the survivors. Mechanical 

 apparatus for catching and destroying them would have been the only way to deal with 

 them after they attained the perfect form. If, however, the hay fields had been cut 

 about a fortnight earlier, I believe enormous numbers would have been destroyed. Hay 

 was cut about the first of July in this district, and just at that time the first perfect 

 specimens of our commonest species Melanoplus femur-rubrum (fig. 7), and M. atlanis 



were observed. Had the hay been cut about the 20th 



June, as it might have been without injury to the crop, 



the greater part of the first brood must have perished. 



In a crop like hay, which covers the ground thickly, 



there is very little active vegetation at the roots, 



to ^ but a great deal of moisture is kept from evapora- 



* IG - ' • ting. As soon as the crop is cut all that is left on 



the fields above the surface is at once dried up by the action of the sun and air 



and the plant does not shoot up again for some weeks. In very wet seasons, of 



course, this takes place sooner. Last July, and the end of June were excessively hot and 



