(11) Xoiniallv, the disease had the effect of delaying inoltiug, or pupaaou, 

 thus leiigtheniiijj the instar. The exceptions were: two grubs in first instar that 

 died respectively four ami twenty-six days after hatching from eggs; and six 

 grubs in third instar tliat died witliin Ihree months after last molting (one m 

 thirteen days and one in two weeks). 



(12) In the case of several grubs that died of this disease, it was noted that 

 the preceding instar was above normal in length, indicating that a rather long 

 jieriod (if infection by the disease precedes the outward and visible signs of 

 disease. 



Infection ol<^ Grubs by Bacterial Disease. 



A very high fatality of grubs in the experimental boxes was 

 caused, or had every appearance of being caused, by a bacterial dis- 

 ease tliat is supposed to be identical witli a disease described as 

 Micrococcus nigrofaciens by Zae Northrop. (See Technical Bulletin 

 No. 18, ^lichigan Agr. Sta,. entitled, "A Bacterial Disease of June 

 Beetle Larvae, Laclinostevna spp.") The symptoms of the disease 

 are a turning black, and final droi)ping off. of one or more of the 

 legs at the joints, and the appearance on the body or head of black, 

 sliining spots, or lesions, which increase slowly in size and may cover 

 consideral)le portions of the body before death finally ensues. These 

 symptoms, as observed in grubs in rearing boxes at Santa Eita, are 

 identical with those described in tlie bulletin by Miss Northrup. 

 Further reason for believing the two diseases identical may Ik- found 

 in a paragraph of that bulletin, which states: "One hundred per 

 cent of larvae received from Porto Rico (IMarch. 191-1) were more 

 01" less infected." 



After examination of tlie breeding notes, a careful compilation 

 was made of the data concerning the infection of sugar cane wliite- 

 grul)s (P. vandinei) by this disease, and as result it was found that 

 sixty-two grubs were noticeably infected, of which number only three 

 ])upated and became adult in spite of the disease. Tlie other fifty- 

 niiji- died, apparently as a result of the disease. 



Only th<^ larval stage is attacked by the disease, eggs, pupae and 

 adults lieitig appai ciitly iiiiiiiuue. Of the sixty-two hii'vae attacked, 

 fiftx-uiiie wei'e ill tlie thii-d instar (which rejiresents .")() per cent of 

 till' total mimhcf reared), and only tlii-ee in the secoiitl instar. No 

 gniiis of tlie first instar were at any time observed .-ittacked l>y this 

 disease. 'I'his is somewh;it at \ariance with the reiiiai-k made In" 

 ,Miss Xorthnip that the younger grups are the iiiore susceptilile. 



it is notable that at no time were grubs collected in the cane fields, 

 or elsewhere out-of-doors, found affected by this disease. Vet within a 

 few weeks' time after they were placed in the confinement of boxes, the 

 (lisej'.se would iii;;ke its apjx'ai'aitce on fifty per cent of tln^ grubs. This 



143 



