OBSERVATIONS ON THE LIFE HISTORIES OF THE STICK INSECTS Acrophylla t"essellata Gray and Ex-tatosmna t"iarat"unl Macleay nv K. KOH.BOOT DEPARTMENT OF ENTOMOLOGY Volume I 1961 Number II lQL 4Zi l ·SJ�t v\ M II OBSERVATIONS ON TI-IE LIFE :HISTORIES OF THE STICK INSECTS A_crophylla tessellata Gray and Extatosom,a tiaratum Nfaclcay by K. KORBOOT Price: Two Shillings University of Queensland Papers Department of Entomology Volume I Number 11 THE UNIVERSITY OF QUEENSLAND PRESS St . Lucia 24th August, IH6l Wholly set up and printed in Australia by WATSON, FERGUSON and COMPANY Brisbane, Q. 1961 Observations on the Life Histories of Acroph.rlla tessellata Gray and Extatosoma tiaratum Macleay (Phasmida) BY KATHERINE KORBOOT, B.Sc. Records observations, extending over two years, on the life histories of A. tessellata and E. tiaratum bred in captivity from eggs laid in the laboratory in January, 1959, by mated females. In both species the incubation period ranged from eight to twenty months. In the development of both male and female A. tessellata each of the six nymphal stadia was approximately fourteen d ys For there were six nymphal stadia for the female, and a . E. tiaratum. five for the male. In the case o.C females of E. tiaratum bred from eggs with an incubation of eight and nineteen months, the duration of each stadii.tm was approximately nineteen days and twenty-four days respectively. Male nymphal stadia were slightly longer than those of the female. The females of A. tessellata were usually found in the summer months on Eucalyptus saplings, but the males, unless taken in copula, were scarcely seen. The males were tree-top dwellers, and with their large, powerful hind wings were able to fly rapidly for a few hundred yards before settling . The females used their wings for gliding from one branch to the next. E. tiaratum was encountered less often than A. tessellata, as both males and females were tree-top dwellers. After storms in the summer months the females were found on young Eucalypt saplings. In both sexes of E. tiaratum the abdomen was fringed with spiny processes . and lamellate expansions, the legs were irregularly dilated, and the cuticle beset with spines. The females were larger and stouter than the males, and somewhat leaf-like in appearance. Their wings, however, were reduced and functionless. The favoured host trees of A. tessellata wete:- E. major, E. grandis, E. maculata, crebra, melanophloia, gummijera, trachyphloia, E. E. E. E. in order of preference, tiaratum e e: major, maculata, tereticomis. tessel­ while those of E. w r - E. E. E. E. laris was not favoured by either species. A constant supply of fresh gum tips was provided for the insects reared in captivity, as they refused withering or stale leaves. The older nymphs and adults readily attacked mature leaves, but the younger nymphs preferred the succulent leaves of the young tips. In absence of gum leaves, young Acacia leaves would be eaten. e Being edge feeders the insects cut off strip after strip of l af , the incision gradu­ ally becoming deeper. They swallowed the tissue whole and after taking one strip of leaf, returned to the starting point to take another strip, no food being consumed in the return motion. Much of the food provided was wasted because of their habit of biting through the leaf near the petiole, resulting in the fall of the leaf blade. They fed irregularly, eating a great deal one day and very little the next. The largest meals were those taken following an ecdysis. Feeding generally took place in the morning and in the evening, the insects remaining motionless at other times. A. tessellata. NS ON TilE L1 FE HlSTORlES UL<' l62 OBSEl<VilfiU STlCK lNSECTS On the .17th January, 1959, a male and a female were taken at Enoggera Crt�ek, a Ashgrove, BrisbanoJ e, and kept in cylindrical 8 in . x 15 in. plastic breeding cag(,, A small branch the food plant, F. maJor, was placed m a receptacle of water m the a cage and the floor of the (�age was covered with layer of sand. Every tiftb chy the leaves wen� replaced w1th fresh ones, and every second day they were sprinkled with water. CojJulation and OvijJosition. The adults copulated on the 20th .J an1tary and remained in cojJula nntil the 1st February, i.e. eleven days. The male took a position 011 the back of the female, witll his fore tarsi resting on her mctathorax, his mid tarsi grasping her second abdominal segment and his hincllegs banging freely cxtcndecl. On the 2nd Fchrua.ry, both the male and female ate ravenously. From the ard Feuruary until the 22nd February, i.e. nineteen clays, tbc female continued to oviposit, laying one llllndrcd and twenty eggs in all. The egg was visible within tbe genital cavity for an hour before oviposition, which , observed on several occasions, was a deliberate egg dropping. The female underwent no change in her position or in tile attitude of her abdomen during oviposition and she displayed no interes t in her eggs. Eight eggs were dropped in the i1rst twenty- four hours of oviposition, seven in each o1 the next four clays, and six on each o1 the remaining fourteen days. An egg was laid at inter vals of from three to four hours, mostly between the hours of 4 p.m. and 4 a.m. Form, Size and TVeight of Eggs. The typical egg of A. tessellata has a slightly curved ellipsoid form, somewhat compressed laterally. O ne end is roun ded , and the other flattened and covered hy the operculum, bearing a crown-like prom inence, the capitulum. 'J'he opercuhtm consists of a fiat platform with an encircling ridge. According to Sharp ( 1898) the operculum is present in all known phasmid eggs. The operculum is fastened to the rest of the chorion hy means of many small tpoth- like ridges which fit into corrcs·­ ponding slits on the inner side of the rim of the egg. 'fhe operculum may be removed without causing injury to the normal functions of the embryo. The capitulum is like a creamish shrivelled cap, and bears a central aperture for the admis sion of air to the embryo. This aperture is surrounclccl by a ring of minute perforations. When freshly laid the egg has a thin coating of varnish-like material wbich dries in twenty to thirty minutes, and gradu ally peels of£ during subsequent development. This coating was also mentioned by Mosca.n<l (1950) as being present on the eggs of Bacillus libanictts Uvarov. When laid the eggs were shining black in colour, becoming dull black when the outer covering peeled off, and changing to grey seven days before eclosion. On the dorsal surface of the egg is the micropylar plate which, according to Moscana, is common to all phasmid eggs. The details of the structure of the plate are different and characteristic in each species, so that this structure has been used as a systematic criterion (Brunner V. Wattenwyl and Redtenbacher, 100f)). The micropylar plate of A. tessellata is long ancl ribbon-like with a spearhead prominence pointing towards the posterior end of the egg. This prominence is black in colour, the rest of the micropylar plate being a <lull grey. The broadened posterior part of the plate, which bears the spe<lrhead prominence, may be called the plate proper. Occupying a central position on the prominence is the aperture of the micropylar canal. K. KORDOOT .163 Length of egg: 2. 70-3.10 mm. Width of egg: 1.65-2.10 mm. Diameter of operculum at its greatest width : 1.00-2.10 mrn. e: Length of micropylar plat l.S0-2.31 mm. There seems be 1�0 rrlati01_1Ship between the of thc micropylar p\ate to �ength . and that of the egg. W1dth of 1mcropylar plate: 0. 7n-0.92 mm. m the plate proper and 0.50-0.72 in the rest of the plate. were Freshly laid eggs cleaned of adhering foreign material and weighed in batches of ten. The average weight was 4.1 milligrams. Incubation of Eggs. The eggs were placed in a 3 in. x 2 in. glass tube with a ·finely punctured plastic top. A piece of moist blotting paper was placed · within the lid and renewed once a week. The tube was kept at room temperature throughout the incubation period. Forty-nine of the eggs hatched on the 30th August, 1959. The remaining seventy-one eggs were kept in the tube, but the moist blotting paper wru; not provided during the rest of the incubation period. Emergence from the Egg. The nymphs hatched at any time of the day or night. At eclosion the nymph raised its head pushing the operculum from the egg capsule. The legs were held downwards under the abdomen in a tangled mass, and not until the head and thorax were the did begin to unravel within ca sule. out of egg, the legs the p The abdomen was flipped out, and then the fore, mid, and finally the hind legs were drawn free of the egg. If at the time of eclosion the egg was very moist, the operculum was not pushed completely the hind s the by the free and leg tended to stick in hinge made not freed th could not be shaken free, and operculum. If mechanically e egg shell the nymph died. The fmt instar, unlike the following instars, was apparently incapable of autotomy o:f the legs. If one hind leg only was caught, the nymph was able to drag the empty shell around until it finally dropped off.