]'.)■. 



■SO I K X T 1 K I A(j R 1 V\j'V IJ R 



21 



iie.ss" of Central Africa; rat-fleas |)lat,ni(' germs; lice 

 typhus fever germs; ete. There is no longer any 

 (h)iiht as to the inter-relaticinships that exist in this 

 part of the web of life. 



Again, fishes furnish anotiier link in the chain (!on- 

 iiecting mos((uitaes and malaria. As is well known 

 certain fishes feed upon mostpiito larvae, aiul in many 

 districts are undoubtedly instrumental iu regulating 

 the amount of malaria. It is believed that the pre- 



Lady beetles ("lady birds." "lady bugs,") or cocclnellids; a, 

 larva; b, pupa; c. imago; all much enlarged. (U.S. Bu. Ent.) 



sence of the small fish called "millions" in Barbados is 

 the reason why that island is so free from malaria. 



Rabbits are not only a direct cause of great losses 

 to the Australian fanners but also indirectly in de- 

 veloping the hlow-fly pest which is very destructive. 



3. — Insects aJid Plajits. 



We are familiar with the enormous losses produced 

 every year by the action of insects and fungous di- 

 seases on our cultivated crops. But we should not 

 fail to look at the other side of the shield, and ascer- 

 tain how many plants are dependent upon insects for 

 their fertilisation and the production of seed. 



Elsewhere (in the Third and Fourth Reports of the 

 Quebec Society for the Protection of Plants) I have dis- 

 cussed the relations between insects and plants, and 

 their value as i)ollinators of useful ]ilants. In this con- 

 nection I may quote Dr. Phillips' remai-ks regarding 

 the value of the honey-bee: "The jiroductiou of mil- 

 lions of dollars worth of fruit depen(is largely on insect 

 pollination, and no insect is so iiiiportant in this work 

 as the honey-bee. It is a most oonservative estimate to 

 claim that the honey-bee does more good to American 

 agriculture in its office as a cross-polliiiator than it 

 does as a honey gatlierer. " 



In the rehilinn of Insects to I'lanI diseases, two 

 aspects present tliem.seh'.es, v'r/.. (1) tjic role of insects 

 as disease-carriers to plants, and (2) the role of fun- 

 gous diseases in destroying insects. 



It is clear that if these relations are to be thoroughly 

 investigated, the economic entomologist must work in 

 close co-operation with the plant-pathologist. 



With regard to the part played by insects as di- 

 sease-carriers to plants. I cannot do better than refer 

 you to the excellent paper by Prof. Caesar read at the 

 last meeting here (1918 Re])ort Ont. Ent. Soc.) and to 

 the article by Mr. E. M. DuPorte in the 11th Report of 

 the Quebec Society for the Protection of Plants, (1018- 

 19) where the sub.iect is fully discussed. 



An interesting relation is tlie double-host relation 

 of many ajihids. Neai'ly ever.v year adds to the num- 

 ber of aphids that have this relation, and future studies 

 will (lerhaps furnisli an explanation of this interesting 



movement in early and late sumnu'r to the host plants. 

 The relation is ot interest to the economic worker as 

 it suggests additional means of control. 



Another inter-relation somewhat closely related to 

 the foregoing is that of useless plants and insects. One 

 instance will suffice. The hawthorns act a-s Ihosts for 

 many insects that are in.jurious to tlie a[)ple. It is 

 clear that the relationship demands more careful 

 stud.y by economic entomologists. 



With regard to the utilization of fungous and pro- 

 tozoan diseases in insect control (1), it may be said 

 that many experiments have been conducted with- 

 in the last thirty years with the ob.ject of controlling 

 injurious insects tlirough the artificial production of 

 epidemics of fungous diseases. As in the case of para- 

 sitism unexpected difficulties have appeared under 

 field conditions. It was soon disco verecl that "fungi 

 are very dependent upon external conditions, and in 

 mauy cases the apparent absence of a particular fun- 

 gus in a locality is usually an index of conditions un- 

 favorable for its development and an artificial intro- 

 duction will be useless" (Glaser). 



Out of the large number of experiments that have 

 lieen carried ont, I shall briefly refer to a few of the 

 most outstanding ones. Franz Tangl in 1892 used 



Australian lady-bird beetle (uovlus cardlnalis), the enemy of the 

 white scale (natural size), a, l.ady-bird larvae feeding on 

 adult female and egg sac; b, pupa; c, adult lady-bird; d, 

 orange twig, showing scales and lady-birds (after Harlatt, 

 U. .S. Dept. Agr.). 



spore emulsioiii--, of " liidri/tis has.^iana" against the 

 caterpillars of the nun moth of Central Eui'oiie. While 

 the experiments were eminently successful in the 

 laboratory where all the infected caterpillars died of 

 ■■muscardine", those cai'ried on outdoors gave negative 

 results. Tidteuf also obtained like results with "Cor- 

 dyceps militaris. '" 



]\Ian.v of Us perhaps ai-e familiar with the work of 

 Snow and Forbes in connection with the artificial use 

 of "Sporotrichum globuliferum '" against chinch bugs. 

 Later Billings and Glenn also carried on experiments 



(1") European botanists, such as DeBary and Tulas- 

 ne. about the middle of the last century called atten- 

 tion to the importance of white muscardine (Isaria 

 (Irusa Link.) a.s a check on many insects. Metchni- 

 koff, and Krassilstscik cultivated the green muscardine 

 {Metarhiziuin awisopliaf Sorokin) for the control of 

 Anisopiia a.nd the beet weevil (Cleanus punctiventris) . 



Efforts have also been made to check the white 

 grid) in Kurope by means of Cordj'-eeps melolonthae 

 Till.. Isfiria fit iixd' and Hnlnjlhs irnclla Sacc. 



