CROSSING EUSCHISTUS VARIOLARIUS AND EUSCHISTUS SBRVUS. 341 



also the nymphs, snck the water from this filter-pa.per, but apparently with 

 no injurious after-effects. We aimed to keep the temperature at 80° Fahr. 

 night and day, and we succeeded in keeping the heat quite constantly at 

 this point by using an electric stove. 



[t requires unremitting care to raise these Hemiptera in the laboratory. 

 They not only require constant watching during the day, but must be 

 examined two or three times in the night. Not only is this necessary for 

 accurate observations, but if the adults or nymphs are found on their backs 

 they can be turned over with a camel's hair brush and their lives thus 

 saved. 



All our records have been kept with the utmost care. We have recorded 

 not only the number and date of the deposition of the eggs, but the date of 

 hatching, the number hatched in each group, the date when each of the five 

 moults occurred, and a record of just how many young survived each moult. 

 This is very important, in order to know the exact number of nvmphs in each 

 wet chamber dish, and thus avoid the danger of unwittingly thowino- away 

 a nymph with the stale food. As a rule, the nymphs from a sino-le batch 

 of eggs were kept separate, but late in the season, when only a few nymphs 

 hatched out from a group of eggs, these nymphs, after the 1st or 2nd moult 

 were added to a cage that contained other nymphs from the same parents. 

 When possible the date and hour of the deposition of each batch of eggs was 

 recorded, though this of course was only possible where the deposition of the 

 eggs was actually observed. In all other cases the time given is only 

 approximate ; but as the food in the cages was arranged to expose to view 

 the places generally selected by the bugs for depositing their eggs, they 

 were not often overlooked, until the food was changed and a closer search 

 was possible. It is very important to secure the eggs as soon as possible 

 after they are laid, for we found that both the male and the female parents 

 will occasionally suck the eggs. Sometimes the male and sometimes the 

 female was found with the proboscis buried in one of the eggs, very busy 

 sucking out the entire contents. They pass from one egg to the next and 

 may destroy a large number of eggs, leaving only transparent empty shells. 



Two sets of records were kept for each pair of bugs, one set recording the 

 history of the parents, and the second set recording the development of 

 their offspring. 



A full copy of these notes would make too voluminous a record to be 

 published here, but in order to compare the breeding habits of variolarius, 

 servus, the crosses and the Fi hybrids, we shall give a condensed extract 

 from these notes, showing for some individual cases, the number of eggs 

 deposited by one female, the relative number that hatched, and the relation 

 between mating and the deposition of eggs. Records I.-XI. pp. 362-70. 



We have frequently watched the hatching of the eggs and the subsequent 

 five moults of the nymphs before they reach the winged stage. Nymphs 

 from the same group of eggs that hatched the same day, or even the same 



29* 



