New Zealand Entomology/Hymenoptera
CHAPTER IV
The Hymenoptera.
The Hymenoptera are perhaps the most interesting order of insects, their brilliant colours, great activity, and unparalleled instincts rendering them alike attractive to the young collector and scientific entomologist. They are, however, not very numerous in New Zealand, several of the most important families being completely absent; in fact, with the exception of the ants, there are no social Hymenoptera native to this country. The information I here give in connection with these insects does not adequately represent the large amount of interest which can be derived from their investigation, and I must therefore refer the reader to those admirable works by Sir J. Lubbock on Ants and by Huber on Bees, which cannot fail to interest all who read them.
Family Andrenidæ.
Dasycolletes hirtipes (?) (Plate III., fig. 1).
This is the true native bee of New Zealand, and may be taken abundantly during the whole of the summer. Its nest is constructed in crevices in the bark of trees, &c., the insect very frequently selecting the spaces between the boards of outhouses, where the loud buzzing noise made by the perfect bees when emerging from their retreat at once arrests our attention. These nests consist of about ten oval cells, formed of clay, and neatly smoothed within. They are all constructed by a single female, which also provisions them with honey and pollen, depositing an egg in each. The larva, after consuming the food, changes into a pupa, from which the perfect insect emerges about January. If the reader will imagine a great number of these nests closely packed together, the formation and storing of the cells being performed by a number of sterile individuals (workers), while the eggs are deposited by a single female (queen), he will have a fair idea of the economy of the social bees and wasps, whose wonderful instincts attain their maximum in the well-known hive-bee, successfully introduced and cultivated in various parts of the country.
Closely allied to this species is Dasycolletes purpureus (?) (Fig. 10), which forms its nests in sand-banks, its cylindrical holes having a great resemblance to the burrows of Cincindela tuberculata, which frequently occur in the same situation.
Family Sphegidæ.
Pompilus fugax (Plate III., fig. 2).
This is a very abundant insect, and may be observed flying about on any fine day during the summer, occasionally stopping to examine leaves and crevices in the bark of trees, where it is looking for the unfortunate spiders, which constitute the food of its progeny. The larva is a fat apodal grub, and may be found in the cells constructed by the perfect insect, which usually selects a large cylindrical hole in a log, previously drilled out by a weevil. Into this burrow she pushes a large quantity of spiders, which she has previously captured and paralyzed with her venomous sting. When her nest is properly provisioned she deposits an egg in it, closes the hole with a neat plug of clay, and leaves the larva to quietly consume its half-dead companions. Each female, no doubt, forms a large number of these cells during the summer. While cutting up old logs for Coleoptera, the entomologist will not infrequently come across these nests, when the insects may be found in various stages of development. Unfortunately, however, the sight which usually meets his eye is a large number of legs and other fragments of spiders, the fugax having long since deserted the burrow, and being very probably engaged in forming others in a neighbouring tree. These insects are very ferocious, and will attack spiders which considerably exceed them in size. On one occasion I noticed a very large one at rest in the centre of its web, which was suddenly noticed by a passing fugax, which immediately sprang upon its back, and, in spite of violent movements on the part of the spider, twisted her abdomen dexterously round and stung her victim in the centre of the thorax, between the insertions of the legs. This produced almost instantaneous paralysis in the spider; but it was apparently too large for the fugax to carry away to her nest, as I saw the unfortunate creature hanging helplessly in its web some hours after the occurrence.
Family Formicidæ.
Formica zealandica (Plate III., fig. 3 ♂, 3a ♀, 3b ☿, 3c, cocoon).
This is one of our commonest ants, and may be noticed under logs and stones throughout the year. The nest consists of a number of irregular cavities dug out by the workers either in the ground or in soft rotten wood. Its size varies considerably, but the societies of this species are not usually so extensive as those of Atta antarctica, an insect I shall have occasion to refer to presently. The larvæ are minute apodal grubs, which are dependent entirely on the workers for food. When full grown they spin an oval cocoon of white silk, in which they are converted into pupæ, and these the patient neuter ants may be observed carrying away with great anxiety when disturbed, risking their own lives to preserve their adopted offspring from destruction. The females, or queens, of which there are several in each nest, do not appear to participate in these labours, but are only instrumental in perpetuating the species, and the same remark applies to the males. A large number of these winged males and females may be observed in the nests about February, the general emergence taking place during that month. At this time they leave their native homes and mount to a great height in the air, and after sporting for some hours they re-alight on the earth, and in a short space of time cast their wings. The neuters at this time are said to carry them away to form fresh colonies, but I have not carried my investigations sufficiently far to verify this in connection with the New Zealand species.
Family Formicidæ.
Ponera castanea (Plate III., fig. 4 ♂, 4a ☿, 4b, larva).
This is a much larger species of ant than the last, but is apparently not unlike it in habits. I have figured a male (Fig. 4) and worker (4a), the female not differing from the latter in any great degree, except in being provided with wings. It will be noticed, however, that the male is very divergent. The larvæ of this insect are covered with numerous minute spines, and may be often found in the nests; also the cocoons which they form when full grown, these latter being of a dark brown colour, and rather elongate. The winged insects are not frequently seen. They appear only for a short time in February, the earlier ones being invariably held captive by the workers until the rest have emerged, when they are all allowed to fly away and form fresh colonies as in the last species.
Family Formicidæ.
Atta antarctica (Plate III., fig. 5 ♂, 5a ♀, 5b, larva).
This is another very abundant species, found occasionally amongst rotten wood in very large communities. Its larva, which is represented at Fig. 5b, does not form any cocoon, the pupa being quite naked and defenceless. It is a beautiful little object when examined with a microscope of moderate power. The annual migration of the winged males and females of this species usually takes place on a hot day in the last week of March, at which time I have observed the air throughout a day's journey absolutely swarming with these little insects. Many specimens are captured in the spiders' webs, while the logs, fences, and ground are covered with ants in the proportion of about ten males to one female. At other seasons of the year the winged individuals of Atta antarctica are seldom observed.
Family Chalcididæ.
Pteromalus sp. (?) (Plate III., fig. 9).
This little insect was reared, in company with thirteen others of the same species, from a pupa of Eurigaster marginatus which had been procured from a larva of Œceticus omnivorus, and is consequently a true hyperparasite.[1] Its curious habits will be better understood by the reader after perusal of the life-histories of those two insects, which I have given on pages 60 and 74. The method by which the females of the Hymenoptera whose larvæ are parasitic on insects inhabiting other insects, introduce their eggs into their hosts,[2] is not at present known to entomologists, but it seems at least probable that they are deposited in the eggs of the parasitic Dipteron before these gain access to the caterpillar of the moth.
Family Ichneumonidæ.
Ichneumon sollicitorius (Plate III., fig. 6).
This is the most abundant of our ichneumon-flies, and may be taken amongst herbage from August till May. Its larva is parasitic in the caterpillars of various Noctuæ, having occurred in the following species: Mamestra composita, M. mutans, and M. ustistriga. The pupa may be frequently discovered inside that of the moth, and is quite white in its early stages, but as age advances all the colours of the future insect can be seen through the thin pellicle which invests it. The perfect insect makes its escape through a circular hole, which it drills in the upper end of the unfortunate moth pupa it has destroyed. The sexes of all ichneumon-flies may be at once recognized by the females possessing an ovipositor[3] differing considerably in length among the various species, but nearly always plainly visible.
Family Ichneumonidæ.
Ichneumon deceptus (Plate III., fig. 7).
This conspicuous insect is chiefly mentioned on account of a very curious habit possessed by the females of congregating in large numbers on matai trees, as many as fifty or sixty specimens being often found huddled together under a single flake of the bark. The males are occasionally taken flying in the open, but I have never seen any amongst these large assemblages of females. Whether the ichneumons are parasitic on some insect which lives on the matai, or whether they assemble to feast on the sweet juice occasionally exuded from its bark, it is impossible to say, but in either case the complete absence of males is a very remarkable circumstance.
Family Ichneumonidæ.
Scolobates varipes (Plate III., fig. 8).
The larva of this little insect is parasitic on the useful larva of Syrphus ortas whose life-history is recorded on page 57. It is very common in some instances, and must consequently destroy a considerable number. It entirely eats the soft portions of the insect, and may afterwards be found lying snugly within the hard empty shell of the deceased syrphus pupa, which acts as a cocoon for it while undergoing its own pupa state. The perfect insect may be often observed amongst herbage, searching for syrphus larvæ to deposit its eggs in.
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