88 



golden rod and asters. Several important factors control the abun- 

 dance of T. inornata, such as scarcity of large grubs in the years when 

 the dominant species occur either as beetles or small grubs. The life- 

 cycle of most species of Lachnosterna is completed in three years, and 

 when full-grown grubs are abundant, plenty of hosts for Tijphia occur ; 

 but the next year only beetles, eggs and small grubs are present and 

 Tiphia then either parasitises grubs of non-dominant species or perishes. 

 A permanent scarcity of grubs is caused by unfavourable agricultural 

 practices, or the absence of trees to furnish a food supply for the 

 adults. Frequent ploughing, rotation of crops, and heavy grazing 

 of meadows and fields by horses, cattle and especially pigs, destroy 

 large numbers of Lachnosterna beetles. Practically all the fields from 

 which the largest numbers of Tiphia cocoons were collected, were of 

 two types, either with several trees of Populus deltoides in or near them,, 

 or near Quercus or mixed woods. P. deltoides and Salix are preferred 

 to oaks and elms by most species of Lachnosterna, and Madura 

 aurantiaca and two species of maple are the only common trees 

 unacceptable to any Lachnosterna beetles. As an adequate supply of 

 Lachnosterna grubs is restricted to areas supporting the favoured 

 trees, the dispersion of Tiphia is checked where they are absent. 

 Unfavourable soil, which favours other parasites of Lachnosterna, is 

 an important factor. Tiphia is abundant on the black clay and 

 brown silt loam, but Elis sexcincta, F., another parasite of Lachnosterna, 

 seems better adapted to the grey clay and sandy, gravelly loam of the 

 hilly and wooded parts of Illinois. There are at least two parasites, 

 a BombyUid fly, Exoprosopa fascipennis, Say, and a Rhipiphorid 

 beetle, Rhipiphorus pectinatus, which attack Tiphia, but these seldom 

 infest more than 1 or 2 per cent, of the cocoons. Autumn ploughing 

 causes premature emergence of the adults and exposure of the 

 cocoons to predatory enemies. 



MiNGwoRTH (J. F.). Further Notes on the Breeding of the Tachinid 

 Fly parasitic on the Cane Beetle Borer. — Jl. Econ. Entom., 

 Concord, vii, no. 5, October 1914, pp. 390-398, 1 pi. 



A thousand grubs of the borer Rhabdocnemis ohscurus, Boisd., 

 parasitised by the Tachinid, Cerojnasia sphenophori, were trans- 

 ported from Hawaii to cane fields in Fiji. During the voyage, 

 about 100 flies emerged from puparia which had been found in the 

 borer cocoons, the emergence invariably taking place in the morning ; 

 all these were placed under inverted glasses and daily supplied with 

 fresh slices of cane and bits of cotton batting saturated in water, 

 care being taken to have no drops of water anywhere. On reaching 

 Suva, Fiji, half the emerged flies were put in a cage stocked with canes 

 containing S. obsciirus, the other half were liberated in badly infested 

 fields ; about 50 flies were put into each of tw^o cages in a drier section 

 than Suva ; the remainder of the parasites, then in the form of puparia, 

 were placed in jars containing damp grass, in the fields, but sheltered 

 and protected from ants ; the next morning these were all found to have 

 been destroyed by rats or mice. Mating observations showed that the 

 flies begin to mate on the same day that they emerge and that a fly 

 can produce upwards of 1,000 young, which are deposited as living 

 maggots and are thus enabled to enter S. ohscurus grubs at once. 



