451 



But how, then, does this bacterial attack cause the disintegration 

 shown by the polyhedral granules ? BoUe says : 



We suppose that the formation of the polyhedral granules is caused by defective 

 respiration: we are led to this belief by the accumulation of these granules, first in 

 the adipose tissue and then at the capillary terminations of the trachete, both of these 

 being parts of the organism whose main function is respiration. Even if this suppo- 

 sition of ours were correct, we are still unacquainted with the prime causes of the 

 spontaneous formation of these granules. It may be regarded as certain that hu- 

 midity, low temperature, and defective ventilation contribute not a little to the 

 grasserie. But we would say that these influences alone can not develop the disease, 

 although it is probable that they increase its intensity ; otherwise we should have no 

 explanation of the sporadic cases of grasserie which are of constant occurrence even 

 among those broods that are most judiciously cared for. 



Per contra, I give Forbes's conclusions : 



Assuming that the mortality was originally caused by the intestinal bacteria, we 

 may suppose that this infection was not sufficiently overwhelming to destroy life by 

 direct action, as seems to be the case in flacherit, but that it nevertheless had the 

 eflect to so disturb the balance of physiological functions as to retard the develop- 

 ment and preparation for pupation of some of the organs, while the fatty bodies, 

 being special stores of material accumulated for use in pupation, and so less promptly 

 and easily affected by causes attacking the general health of the larva, went on to 

 pupation and experienced the histolysis characteristic of that phenomenon. In 

 othe/ words, we may suppose, quite consistently with all the facts, that a relatively 

 slight bacterial attack took uneven eSect on the various parts of the animal and not 

 immediately destructi ve effects on any ; that it retarded the preparations for pupa- 

 tion of the great vital organs, but that the fatty bodies, as if unaware of this fact, 

 continued their course of maturation and histolysis, reaching a condition of pupal 

 disorganization before pupation had actually occurred (p. 280). 



OBSERVATIONS ON INJURIOUS AND OTHER INSECTS OF 

 ARKANSAS AND TEXAS. 



By F. M. Webster. 



Acting under Dr. Riley's instructions, I left home on February 2, and 

 stopping a couple of days in southern Indiana to make some observa- 

 tions on strawberry insects, more especially Ealtica ignita, reached 

 Memphis, Tennessee, on the oth instant. The object in visiting this 

 locality and eastern Arkansas was to secure some data with respect to 

 the early stages of the several species of Buffalo Gnats. Xo difficulty 

 was experienced in finding the exact locality, a short distance to the 

 southeast of Memphis, where Dr. Lugger studied Simulium in 1886, but 

 the stream was so swolleu by recent rains that wading was rendered 

 impossible, and as no boat was obtainable a critical examination was 

 rendered impracticable. 



At Madison, Arkansas, where I had studied the habits of various spe- 

 cies of Simulium during 1887 and 1888, very many larviii were found in 

 the swiftest flowing portions of the St. Francis River, being attached as 

 usual to young willows and cottonwoods growing in the stream. Some 



