56 EXPERIMENT STATION RECORD. [Vol.43 



up to the beginning of August. Between the last appearance of H. Uneatum and 

 the first of H. hovis there is usually a period of 10 days when the cattle are 

 immune from attack of either species. H. hovis frightens the cattle much 

 more than //. Unentum. 



"The eggs take about a week to hatch; the larv.ie bore througli the skin in 

 the coarser, porous parts, taking several hours in the process; at this stage 

 they are about 1 mm. long. The lesions resulting from this penetration are 

 caused partly by anaphylactic reactions and partly by bacterial invasion, those 

 produced by H. Uneatum being the more severe. For the skin lesions the name 

 ' hypodermal rash ' has been proposed. 



"At this point there is a hiatus in the life history. It is not positively known 

 how the larvfe reach the esophagus, where they are subsequently found ; most 

 likely they travel in the loose connective tissues under the skin up to the region 

 of the throat and into the esophagus where the umscles bifurcate. Passing 

 down the esophagus they follow the submucosa and are almost always found 

 lying along the long axis of the canal. Whilst in the esophagus, small edmatous 

 swellings are found surrounding the grubs. These are sterile and are anaphy- 

 lactic in character ; the exudate contains large numbers of eosinophilic leuco- 

 cytes. The earliest record made at Agassiz of larvre in the esophagus was on 

 August 15, when a larva 3.4 mm. long was found and several, slightly larger. 

 Continental observers have recorded smaller larva? than this. 



" H. Uneatum makes its appearance in the backs of cattle about December 

 15, and H. hovis about a montli later. Tlie larvre at this time have grown 

 about 1.5 cm., and are similar in size to tliose which are found in the neural 

 canal and under the skin. At this stage it is difficult to separate the larvje 

 of the two species, but Bisliopp has recently discovered good distinguishing 

 marks between them. The life histories overlap at this period, making it 

 difficult to follow the migration, but in the latter part of the season (the mid- 

 dle of March) the last larvse to leave the esophagus are at the paunch end. 

 They pass out under the pleura and go to the neural canal, either up the crura 

 of the diaphragm or up the posterior boi'der of the ribs, entering the canal by 

 the i)Osteri()r foramen. The larva evidently makes iise of the canal as an 

 easy means of access to the lumbar region, the part of the animal which is 

 best suited for passing its last stages within the host. The larv?e follow con- 

 nective tissues exclusively, and no larvse have been discovered in muscular 

 tissue. The mature larvse leave the animals' backs from the early part of the 

 year up to the first days of July. 



" The periods for the two species have not been fully worked out ; but, judg- 

 ing from what records there are of the pupal period and the time of year 

 that flies are on the wing, H. Uneatum begins to emerge in February and 

 finishes about May 1. H. hovis begins about May 1 and ends approximately 

 on .July 1. The average pupal period for H. hovis is 32.5 days for H. Unea- 

 tum a little less. The duration of the life of the flies is short, seeing that they 

 can not feed. This life history applies to Agassiz, B. C. ; doubtless in other 

 countries variations will be noticed, but the period spent by the larvse within 

 the host must be of the same duration, seeing that animals' temperatures are 

 the same the world over." 



As a means of prevention it is reconmiended that animals be housed during 

 the heat of the day to prevent the flies laying upon them. Warble grubs should 

 be squeezed out as early as possible during the year. This method will lessen 

 the damage to animals and their hides. If the total eradication of the pest is 

 attempted, cooperative measures must be undertaken. 



Fruit flies of the genus Dacus sensu latiore (Diptera) from the Philip- 

 pine Islands, N. Bezzi {FhiUppine Jour, fe'cr., 15 {1919), No. 5, pp. 41I-443, 



