Live identification

identify insects at the logs

Why identification?
Many of the insects found at the logs live fascinating lives and are amazing to look at in close-up detail. It is only too easy to be intrigued, but the time soon comes when you start to recognise some regulars and want to know more about them; this requires at least a  degree of identification. The digital camera has allowed freedom to capture many views of the insects, from varying angles, while drilled logs set out on a south-facing wall have been proven to draw in numbers of species of hymenoptera in particular. Another wonderful tool has been the availability of low-priced binoculars developed for studying butterflies in close-up. 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 do this, and many are quite safe to identify as they appear in the wild. 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 added as a pattern is discerned and useful features noted.


- Basitarsus            top segment of the tarsus, at bottom of leg
- Gaster                 hymenopteran abdomen
- jizz                      general recognition of insect
- Pubescence          hairy surface
– Scopal brush        pollen basket beneath gaster
- Sternite               segments seen beneath the gaster
- Tergite                 segments visible above gaster
- Thorax                 major body section between head and gaster



Species nesting in wood: Osmia bicornis, caerulescens, leaiana

Females (with bushy pollen baskets beneath the abdomen, usually smothered in pollen)

1. Scopal hairs GOL or BRIGHT ORANGE                                                                                                                                                                                                                       2.

- Scopal hairs BLACK                                                                                                                                                                                                                                                      3.

2. Dark head and top of thorax metallic bronze-green; HORNS at side of clypeus (see 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.             



- Head and top of thorax black; 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.        


 3. Top of thorax polished and lacking microsculpture; body integument black, tinted metallic BLUE and covered with greyish hairs; face without horns; only slightly dusky wings; hair bands at the edges of the abdominal segments; GREY leg hairs; scopa BLACK; 7-11mm.


 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; 7-13mm.



- 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; 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.                                       


- GOLD-BRONZE head and thorax; PALE face hairs; short brown leg hairs; tarsi with short red-gold hairs; 9-10mm.


 Although photographs are shown after each description, it may be helpful to put a smaller copy of each together, so as to make comparisons easier.


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 hairs, particularly those on the top of the insect, so as to appear almost white. Visual identification is a question of detective work on numbers, rather than concentration on one specimen. With experience comes a sense of ‘jizz’, but this is only an aid to becoming more familiar with the insects visiting log-nests.

 FEMALES - short antennae, dense scopal brush

M. willoughbiella is the odd one out in this set, notable for not being one of the others, rather than with definite obvious features. She varies a great deal both in colour and the extent of wear and tear. If you spot the long black hairs on the last gastral segment (1), it will be clear it is not M. centuncularis, which is a very distinctive bee.

1.    From the side, long black hairs emerging from matted hairs on last visible gastral tergite 6                                                                                                                    2.

-    Minute black matted hairs only on gastral tergite 6                                       3.

 2.    ‘FULL-LENGTH,’ fringed, golden to red-haired pollen basket (seeming all one colour, though the final two sternites are actually white haired). Hairs on head, thorax, and gastral tergites 1 to 2, SNOW-WHITE. Tergite 5 with a conspicuous fringe of white or yellow pubescence. 9-12mm



   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. Tergite 2 without, 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    


3.    Scopal hairs on sternites 2-4 rich, deep, GOLDEN-RED; hairs on 5, and base of 6, BLACK. 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


-    Scopal hairs on gastral sternites 2-4 golden, 5 and 6 black. Skimpy, barely obvious, pale bands on dark gaster, widely interrupted in centre. 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


 MALES  - long antennae, no pollen basket
1.    Pale front basitarsus, EXPANDED & flattened. 10-12mm


- Front basitarsus cylindrical and black                                                             2.

2. Dark head with pale hairs; 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


-   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


- 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



As previously, I believe it is helpful to put a copy of each species photograph into a group for comparative purposes.


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 find out what general grouping they fall into, which can prove difficult with conventional keys. The following list should enable people to come to grips with a general idea of the commoner groupings - sufficient perhaps to get a book or go online to be more certain.

Chrysidids - Brilliant red and or blue-green cuckoo, or jewel, wasps

Coelioxys -Cuckoo bees with distinctive tapered and pointed abdomen

Crossocerus -Small dark digger wasps, with short constricted segment between abdomen and thorax

Ectemnius - Black wasps with yellow banded  or marked abdomens

Gasteruption - Peculiar looking small parasitic wasps with their abdomen looking as if it arises from the top of the thorax, long ovipositor in female

Hylaeus - Tiny black bees looking like wasps, with white or yellow markings on their face and other parts

Ichneumons - If an insect is seen with long ovipositor sticking out behind, it is almost certain to be a female from this group

 Passaloecus - Small dark wasp with a long slender segment between abdomen and thorax

Pemphredon - Small densely hairy wasp similar to the largely hairless Crossocerus wasps

Psenuslus - small dark wasp like Crossocerus, but with stouter antennae, particularly female

Trypoxylon - Dark elongated wasp with the abdomen projecting well beyond the wings

CROSSOCERUS digger wasps are the third main group, other than leafcutter and mason bees, likely to be found round the logs on any typically busy day. Small, slender black wasps fly round the holes, testing for the presence of females and, later, females search for the best nest sites. There are great numbers of these around whenever the sun comes out. It may be helpful to list those that might be found in this area, using logs or bamboos for nest sites. At least this cuts the list of possibles down.

C. annulipes - dark, flies from May to September

C. binotatus - black wasp with yellow banded abdomen, flies from June to September

C. capitosus - dark, flies in June

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

Top - flats insects


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