﻿80 BUlxLETlK 1369, tJ. S. DEPARTMENT OF AGRICULTURE 



DESTRUCTION BY BIRDS AND MAMMALS 



Birds undoubtedly destroy many larvse as they drop to the ground 

 after emerging from the backs of cattle. The pupae also are subject 

 to attack, since they often remain exposed on the surface of the 

 soil or only slightly covered. Several instances were observed 

 in New York in which robins {Planesticus nnigratoHus) devoured 

 larvse of H. hovis with avidity. In one case a larva under observa- 

 tion as it burrowed into the soil was seen by a robin sitting on a 

 fence. The robin flew down, picked up the larva, and escaped with 

 it before the bird could be frightened away. This larva was almost 

 covered by the soil as it burrowed in. Species of the larger ground 

 birds undoubtedly destroy many larvae. Henry Poison of Mountain- 

 view, Wyo., makes the following statement: "Sometimes magpies 

 pick holes in the backs of the cattle, trying to get the grubs out, 

 causing sores." In rather extensive observations made by one of 

 the writers in areas where magpies (Pica pica hudsonia) abound, 

 this action has not been seen, hence it is thought to be rare. 



Many larvae which emerge from cattle in the barnyards where 

 poultry range are destroyed by fowls. Chickens have been observed 

 to devour greedily considerable numbers of mature larvae when fed 

 to them. 



It is probable that small rodents destroy many larvae and pupae. 

 Stegmann (-94) states that the pupae on the ground are destroyed 

 by moles. 



INSECT ENEMIES 



No predacious insects have been observed to attack the larvae or 

 pupae of Hypoderma in the United States, and it is thought that 

 they are not an important factor in control. 



No parasites have been found in nature, but very few pupae have 

 been recovered after exposure in fields. The writers have reared a 

 considerable number of specimens of Nasoma hrevicorms Ashm. from 

 pupae kept in screen cages in an outdoor insectary, in more or less 

 close association with parasitized pupae of muscoid flies. 



A. Gansser, of the Warble Committee of Switzerland, states in a 

 letter that he thinks that a hymenopterous parasite which has not 

 been determined is an important factor in control in that region. 



FUNGOUS GROWTHS 



The writers have observed the growth of molds on and in the 

 puparia of Hypoderma, and there is some reason to believe that the 

 insects may be attacked in some cases. Lucet {63) expresses the 

 opinion that in France certian fungi destroy the pupae. 



EFFECT OF SUBMERGENCE ON LARV^ AND PUP^ 



In 1921 a considerable number of extracted larvae of H. lineatum 

 were submerged in water for periods ranging from 3 to 23 hours. 

 These periods apparently had very little effect on the larvae; at least 

 the percentage found dead at the end of three days was not greater 

 than in the untreated groups. During 1922 five mature larvae were 

 submerged from I14 to 19 hours. The larva submerged the shortest 

 period produced an adult in normal time, but the four submerged 



