IS AUSTEALIAN SUGAE-CANE BEETLES AND THEIR ALLIES. 



ill wliich, on an extremely hot day, he saw hordes of beetles fly and take 

 shelter on the shady side of the trunks of large trees, lining them from 

 3 to 50 feet. 



Ovipositing. 



Prior to the season of 1920-21 we had little direct evidence as to the 

 ovipositing of these beetles in the field, for most of the observations had 

 been made in pots of soil in the insectary, where the beetles were naturally 

 limited as to depth. These observations, however, coincided with those 

 made by Tryon (19) in which he states: — 



""When about to lay its eggs the beetle enters the ground to a depth 

 of about 6 inches, or even sometimes to a less depth. This habit is 

 displayed when the beetle is confined under experimental conditions, but 

 it seems that it is highly probable that it is also manifested in the field, 

 since what appears to be the eggs of the beetle have been turned up 

 whilst hoeing the sugar-cane in December. The beetle then executes a 

 rotary movement of its body, and so, by forcibly compacting the soil 

 surrounding it, j^rodnces an oblong cavity measuring about 1^ inches 

 long and Ij inches wide. This has smooth walls internally, but the latter 

 are not specially lined, as is the case with the chamber wherein the 

 chrysalis or pupa lies. The latter is also of a much more regular and 

 symmetrical shape than is the egg-chamber. In this cavity the eggs 

 are laid one on the other to the number of twenty-five or sometimes less. 

 These are usually compacted together like those of a carpet-snake, the 

 yielding envelopes of individual eggs often .showing evidences of having 

 undergone pressure from those that have surrounded them. The eggs 

 usually fill the egg-chamber, and, if this does not happen, fine earth 

 that falls in from above assists in doing so. Beetles when confined in 

 In-eeding-cages have also been noticed to deposit their eggs singly in the 

 earth, and they may therefore be expected to display this habit sometimes 

 also Avhilst living under natural conditions." 



I have been able to locate only two definite published observations 

 of the finding of egg-chambers under natural conditions in the field. 

 Girault and Dodcl {66) found a cluster of 11 eggs in a rude cavity in dry 

 clay loam of natural forest, at a depth of 7 inches; and some time later 

 Dodd (91) located a single set of 13 eggs directly under a cane-plant in 

 red volcanic soil, at a depth of 5 inches. 



The above formed slender evidence on which to base a conclusion ; 

 yet the general inference has been that the eggs, in fields of sugar-cane, 

 are normally deposited in chambers directly under the cane-stools and at 

 a depth of approximately 6 inches or less. 



In order to clear up this matter once for all, I started a series of 

 experiments during this past season (1920-21), placing gravid beetles 

 in cages both in the insectary and under natural conditions in the field. 

 Observations in the insectary agreed in the main with what Mr. Tryon 

 has recorded, but in every case the egg-chambers were located right at 

 the bottom of the flower-pots ; so the beetles were evidently limited as to 

 the depth that they might have gone. This was strongly demonstrated 

 in the large field-cage, from which I got most instructive results. 



This cage was made of wire gauze and located in the garden, where 

 the soil had been avcU ploughed. On 31st December, ]920. it was supplied 

 with 21 gravid female Ix'etles that had been collected from the cane-leaves 

 immediately following tlie morning flight. The soil was well watered. 



