1 882.] Entomology. ' 825 



structures for them. From all this I conclude that they have 

 their principal, perhaps exclusive, seat in the alimentary canal. 



Similar experiments made upon chinch bugs taken from the 

 field, gave similar results throughout ; but nothing of the sort 

 could be detected in the fluids of corn plant louse {Aphis maidis) 

 feeding upon the same stalks, nor in any of a number of insects 



To-day (Aug. 17) I noticed that the chinch bugs in the field 

 from which most of those experimented on were taken, were much 

 less numerous than three weeks ago ; and many dead bugs, both 

 young and old, were found behind the sheaths of the corn. The 

 mortality, from whatever cause proceeding, had evidently taken 

 principal effect on the older individuals, as in this field not more 

 than two per cent, of those living had reached the " pupa " state, 

 and no winged specimens were seen, while in other fields, from 

 half a mile to a mile distant, about nine-tenths were pupae, and 

 many adults occurred. I collected a number of bugs, both living 

 and dead, from this situation, and found the Bacteria excessively 

 abundant in all examined. 



The objectives used in these studies were usually Beck's tenth- 

 inch water immersion and a No. 7 Gundlach. For a more care- 

 ful study of the Bacteria, and for a comparison with Bacterium 

 termo, I used, in conjunction with Professor T. J. Burrill (whose 

 studies of Bacteria are well known), a tenth-inch Spencer's homo- 

 geneous immersion and a fifteenth-inch Tolles' of recent make, 

 likewise a homogeneous immersion lens.— S. A. Forbes, State Lab. 

 cf Nat. Hist., Normal, III. 



On the Mouth of the Larva of Chrysopa. — Recently I had 

 the opportunity of watching in a live box, under a low power of 

 the microscope, the seizing and devouring of some plant-lice by 

 the larva of an undetermined species of Chrysopa, and was inter- 

 ested in the manner in which it emptied the body of its victims. 

 The jaws are large, hooked, pointed and tubular, with a small 

 opening at or near the points. Approaching its prey the body of 

 the Aphis is grasped by the hooked mandibles which at the same 

 time pierce it. The Chrysopa larva remains stationary, and pro- 

 ceeds to pump its victim dry. At the base of each of the man- 

 dibles the integuments are dilated into a sac-like form capable of 

 expansion and compression at will, a portion of the thorax is 

 similarly constructed, and it is by the repeated dilating and com- 

 pressing of these sacs that the fluid contents of the body of the 

 Aphis are transferred through the tubular mandibles to the 

 stom ach of the Chrysopa larva. 



when the abdomen of the Aphis has been emptied, the points 

 of the mandibles of the Chrysopa larva are thrust in the thorax, 

 and forward into the head in every direction, and in a few mo- 

 ments nothing remains of the once plump plant louse but a 



