all pictures © robin williams
help to identify insects at the logs
digger wasp Crossocerus megacephalus, taking debris from nest
Many of the insects found at the logs live fascinating lives and are amazing to examine close-up. It is only too easy to be intrigued, but the time soon comes when you start to recognise regular visitors and want to know more; familiarity requires at least a degree of identification. The digital camera has given freedom to capture many views of the insects at no extra cost, from varying angles. Drilled log on a south-facing wall have been proven to draw in numbers of species of Hymenoptera in particular. All this adds up to a simple need to build up knowledge so as to enjoy the experience more.
The purpose of this section is to provide a reliable preliminary identification of the insects as they fly round the logs and bamboos at the 'flats'. While some will remain mysteries unless specimens are taken, I have reached the stage in life where I do not want to take these. Many are quite safe to identify as they appear in the wild, while increasing familiarity will add to the range of those recognised. By careful examination of the many photographs taken during each season, combined with features from reliable keys, there are small groups that respond to this treatment. To recognise some, where only a limited number of species are likely to be present, is much easier than toiling through a long key, depending on microscopic features. Osmia and Megachile fit this pattern and should enable people to get to grips with their identification at log trap-nests. Other groups of insects may be added as a pattern is discerned and useful features noted. The first step in identification is to determine and list those that are likely to be in your locality. This research will not be wasted, cutting down laborious time in examining many unlikely species, because of nesting habits, time of year, records in recent years and so on.
Colours and appearance in these keys are based on LIVE INSECTS, not dead specimens
Some terms in use
- Basitarsus top segment of the tarsus, at bottom of leg
- Gaster hymenopteran abdomen
- jizz general recognition of insect by its behaviour
- Pubescence soft, hairy surface
– Scopal brush pollen basket beneath the gaster
- Sternite segments viewed from beneath the gaster
- Tergite segments visible above the gaster
- Thorax major body section between head and gaster
VISUAL IDENTIFICATION OF BRITISH MASON BEES Osmia
Species nesting in wood: Osmia bicornis, caerulescens, leaiana
Females (with bushy pollen baskets beneath the abdomen, often seen smothered in pollen)
1. Scopal hairs GOLD or BRIGHT ORANGE 2.
- Scopal hairs BLACK 3.
2. Dark head and top of thorax metallic bronze-green; HORNS at side of clypeus (see red line on picture); RED-GOLD hairs covering top of abdomen; hairs on lower legs bushy RED-GOLD; face with dark to black hairs; slightly dusky wings; 9-14mm.
Osmia bicornis f - note horns on head
- Head and top of thorax black; eyes GREEN: face without horns; gastral tergites golden; tergites 2-5 appearing HAIRLESS, the sides fringed with yellow hairs; hairs on lower legs pale, with some gold; wings definitely SMOKEY; 9-12mm.
Osmia leaiana f
3. Top of thorax polished and lacking microsculpture; body integument black, tinted metallic BLUE and covered with greyish hairs; face without horns; dark eyes; only slightly dusky wings; hair bands at the edges of the abdominal segments; GREY leg hairs; scopa BLACK; 7-11mm
Osmia caerulescens f
Males (no pollen basket, unobtrusive hairs beneath abdomen; constantly visiting nest holes in flight, without resting)
1. EXTRA-LONG antennae; dark head and dark bronzed thorax; face hairs distinctive WHITE; upper part of abdominal tergites 1-3 densely clothed with long ORANGE hairs.
Osmia bicornis m
- More 'normal'-sized antennae. 2.
2. Head & thorax BLACK, with blue lights; PALE face hairs; head & thorax with reddish hairs which quickly wear to show much black skin; dark eyes; distinct GREY bands at the edges of tergites, but these wear down to show dark, bare appearance; pale neutral to almost white leg hairs; 7-10mm.
Osmia caerulescens m
- GOLD-BRONZE head and thorax; PALE face hairs; GREEN eyes; short brown leg hairs; tarsi with short red-gold hairs; 9-10mm.
Osmia leaiana m
Although photographs are shown after each description, it is useful to put a smaller copy of each together, so as to make comparisons between sexes and other species more obvious.
O. bicornis f m
O. caerulescens f m
O. leaiana f m
Megachile: VISUAL IDENTIFICATION of BRITISH LEAFCUTTER BEES
Species nesting in wood Megachile centuncularis, ligneseca, versicolor, willughbiella
Male bees are difficult to differentiate, but the generally easier identification of the females should provide a guide as to what is currently flying. However, age may fade the hair colour, particularly on the top of the insect, such as to appear almost white. Visual identification is a question of detective work on numbers, rather than concentration on one insect. With experience comes a sense of ‘jizz’. This is just an aid to becoming more familiar with the insects visiting log-nests. Species are not easy to differentiate, though continued observation over a period will bring differences to light.
FEMALES - short antennae, dense scopal brush
1. From the side, long black hairs emerging from matted hairs on last visible gastral tergite
- Minute black matted hairs only on gastral tergite 6 3.
(this start-pair is conventional, but daunting, unlikely to be observed in the field. For all practical purposes go directly to the pictures and main descriptions)
2. ALL golden to red-haired pollen basket (seeming all one colour, though the final two sternites are actually white haired); dark eyes; Hairs on head, thorax, and gastral tergites 1 to 2, WHITE. Tergite 5 with a conspicuous fringe of white or yellow pubescence. 9-12mm
Megachile centuncularis f
- Middle of gastral sternites 1-4, scopal hairs golden, not obvious from above; the brush on sternites 5 & 6 black. Plentiful golden-brown hairs on black head, sides and back of black thorax: dark eyes; tergite 2 without bands, tergite 3-5 with, pale bands interrupted in middle, widely so on tergite 5, easily abraded with age, leaving wide, complete bands of sparse, ginger hairs. Front legs and basitarsus obviously but more or less hairy. This bee varies greatly in colour with age but one real characteristic is that the last visible segment of the gaster is TRIANGULAR, both above and from the side. 12-15mm.
Megachile willughbiella f
3. Scopal hairs on sternites 2-4 rich, deep, GOLDEN-RED; hairs on 5, and base of 6, BLACK; eyes dark, gastral tergites 3-5 fringed with faint bands of white pubescence, widely interrupted in the middle. Back margin of last visible tergite evenly rounded. 10-13mm
Megachile versicolor f
- Scopal hairs on gastral sternites 2-4 golden, 5 and 6 black. Skimpy, barely obvious, pale bands on dark gaster, widely interrupted in centre; dark eyes; large, bulky bee; margin of gastral tergite 6 broadly rounded, almost cut off in the middle, giving a RECTANGULAR appearance to a long gaster. 15-18mm
Megachile ligniseca f
MALES - long antennae, without pollen basket
1. Pale front basitarsus, EXPANDED & flattened. 10-12mm
Megachile willughbiella m
- Front basitarsus cylindrical and black - normal 2.
2. Dark head with pale hairs; dark eyes; white hairs on side of thorax and edging the front of the abdomen (when fresh, these are gingery but quickly settle to much paler). Greyish, sparse brush beneath gaster; pale sparse, long-haired bands on top. Gaster more rounded than female, but substantial, with same RECTANGULAR appearance. Large. 12-15mm
Megachile ligniseca m
- Pale hairs on head and edges of the thorax. The last two segments of gaster with white bands; the 3rd segment with widely interrupted band. 10-12mm
Megachile versicolor m
- Hairs on head and edges of thorax, golden-white; Gastral tergite 2 with long erect or sub-erect pale golden or whitish hairs in the middle. Pale, unobtrusive, sparse bands on gaster. 9-12mm
Megachile centuncularis m
As previously, it is useful to put a copy of each species photograph into a group for comparative purposes.
M. centuncularis f m
M. versicolor f m
M. ligniseca f m
M. willughbiella f m - note swollen front leg
GENERAL ID FOR SOME COMMONER GROUPS
Keys are complicated things and require hours of work on dead specimens to come up with reasonable results. Those of us looking to identify the insects visiting our logs and bamboos are only too pleased to even find out what general group they fall into, which can prove difficult with conventional keys. The following ought to enable people to come to grips with a general idea of the commoner groupings - sufficient perhaps to go online to be more certain. An English of scientific name entered in a search, with 'pics' added, will bring surprising results - not always correct, but a general trend of good identification should emerge.
Chrysidids - Brilliant red and or blue-green cuckoo, or jewel, wasps
Coelioxys - cuckoo bees with distinctive tapered and pointed abdomen
Coelioxys inermis f
Crossocerus - small dark digger wasps, with short constricted segment between abdomen and thorax
Crossocerus annulipes f
Ectemnius - black digger wasps with yellow banded abdomens
Ectemnius continuus f - bringing a fly as prey
Gasteruption - peculiar-looking small parasitic wasps with their abdomen looking as if it arises from the top of the thorax, long ovipositor in female
Gasteruption jaculator f
Hylaeus - tiny black bees looking like wasps, with white or yellow markings on their face and or other parts
Hylaeus communis m - tiny cuckoo bee, 6-8mm
Ichneumons - If an insect is seen with a long ovipositor sticking out behind, it is almost certain to be a female from this group
Perithous scurra f
Passaloecus - small dark digger wasp with a long slender segment between abdomen and thorax
Pemphredon - small densely hairy digger wasp, similar to the largely hairless Crossocerus spp., with long slender segment between gaster & thorax
Pemphredon lugubris - hairy head is notable feature
Psenulus - small dark digger wasp like Crossocerus, but with stouter antennae, particularly female
Trypoxylon - dark, elongated digger wasp with the abdomen projecting well beyond the wings
Trypoxylon attenuatum f
Crossocerus digger wasps are the third main group that may be come across, other than leafcutter and mason bees, around the logs on any typically busy day. Small, slender, black male wasps fly round the holes, testing for the presence of females while later, females search for the best nest sites. There are great numbers of these around whenever the sun comes out. This list shows those that might be found in this area, using logs or bamboos for nest sites; helping reduce the list of possibilities.
C. annulipes - dark, flies from May to September
C. binotatus - black wasp with yellow banded abdomen, flies from June to September
C. cetratus - dark, flies from May to August
C. dimidiatus - black wasp with yellow-banded abdomen, flies from May to August
C. distinguendus - dark, flies from June to August
C. elongatulus - dark, flies from May to September, probably the commonest
C. megacephalus - dark, flies from May to September
C. nigritus - dark, flies from May to August
C. podagricus - dark, flies from May to August
C. styrius - dark, flies from May to September
C. tarsatus - dark, flies during mid-summer
Some identification points - possible wood-nesting digger wasps in the locality