10 i IOWA ACADEMY OF SCIENCES. 



of insects. Larvse from without could not possibly enter, a leap of two feet being 

 far beyond their powers, a few inches being the most that they can rise. The proba- 

 ' bility of the adults entering the enclosure, even if any had been found elsewhere, 

 was very slight indeed. As soon, however, as larvae appeared over grass land in gen- 

 eral, and they appeared in millions within a few days of the time that the first 

 larvse were found, this pen also contained larvae in numbers, showing, we believe, 

 that the eggs must have been deposited withm that particular area the fall pre- 

 ceding. This observation coupled with the fact that the eggs of the summer 

 broods have been found inserted under the epidermis of grass blades seems to give 

 conclusive proof that the spring brood of larvae hatch from eggs that have been de- 

 posited in the grass in the autumn or early winter preceding. 



The first larvae were seen April 28d, in grass, on the south side of one of the 

 •college buildings, but were not to be found elsewtiere, nor did they appear in great 

 numbers till May 12th, evidently being retarded by the cold wet weather. The 

 larvae taken April 2.3d were nearly black in color and developed into Deltocephalus 

 inimicHS, one adult being obtained .June 29tb. Larvae of the same species, belong- 

 ing to later bro( ds, are usually much lighter colored, almost whitish, with occa- 

 sional individuals of darker color, and after first or second moult all present a 

 characteristic marking, consisting of a black lateral margin to thorax and abdomen. 

 Larvffi of D. inimicus and D. debilis, though very similar when first hatched, are 

 readily separated after the first or second moult by this character, debilis being 

 uniformly light, through the first two or three moults which have been observed. 



Deltocephalus inimicus has been pretty carefully studied and its life history is 

 quite complete. The eggs have been found inserted beneath the epidermis of blue 

 grass blades, forming minute blister-like swellings near the tips, the end of the 

 tips beyond the point of oviposition turning yellow and dying in all the cases 

 examined. By pressing the blisters the incubating insects can sometimes be 

 extruded through the slot made by the ovipositor, and the young insects have been 

 reared from such blades when put in breeding jars. 



July 8th some adults were caged on growing bluegrags and had all died by the 

 15th of July. July 25th larvae appeared in the cage. The period of incubation, 

 therefore, when subjected to breeding jar conditions, would not be less than ten 

 nor more than seventeen days. 



Five distinct stages of growth are known, young larvae, first, second and third 

 moults, the last producing the pupa stage, and lastly the imago. Moults occur at 

 intervals of seven or eight days depending somewhat upon temperature, and some 

 insects that hatched July 25, matured August 26. When ready to moult the 

 insect ascends some blade of grass, fastens its legs to the edge of the blade, and so 

 far as observed with the head invariably upward. The old skin splits along the 

 median line of the head and back and the soft creature struggles out, grasshopper 

 fashion, leaving its cast clinging to the grass. When fii-st moulted it is very soft 

 and transparent, the heart showing as a reddish streak along the back. The dark 

 lateral stripes do not characterize the specimen until about an hour after the moult 

 occurs. 



Deltocephalus debilis. We captured the first specimens of adult debilis June 2d, 

 ten days or two weeks before any adults of inimicus were taken, though as before 

 stated the first larvae found developed into inimicus at a later date, June 29th. 

 By July 7th the first brood of debilis had nearly disappeared. Adults of debilis 

 confined in breeding jars June 3d, died in about ten days, and larvae hatched in 

 these jars July 5th, so the period of incubation of this generation and with breed- 



